Publications

@article{Ikuta2019,

title = {Frequency-Multiplexed Photon Pairs Over 1000 Modes from a Quadratic Nonlinear Optical Waveguide Resonator with a Singly Resonant Configuration},

author = {Rikizo Ikuta and Ryoya Tani and Masahiro Ishizaki and Shigehito Miki and Masahiro Yabuno and Hirotaka Terai and Nobuyuki Imoto and Takashi Yamamoto},

url = {https://link.aps.org/doi/10.1103/PhysRevLett.123.193603},

doi = {10.1103/PhysRevLett.123.193603},

year  = {2019},

date = {2019-11-08},

urldate = {2019-11-08},

journal = {Phys. Rev. Lett.},

volume = {123},

pages = {193603},

organization = {arXiv},

abstract = {We demonstrate a frequency multiplexed photon pair generation based on a quadratic nonlinear optical waveguide inside a cavity which confines only signal photons without confining idler photons and the pump light. We monolithically constructed the photon pair generator by a periodically poled lithium niobate (PPLN) waveguide with a high reflective coating for the signal photons around 1600 nm and with antireflective coatings for the idler photons around 1520 nm and the pump light at 780 nm at the end faces of the PPLN waveguide. We observed a comblike photon pair generation with a mode spacing of the free spectral range of the cavity. Unlike the conventional multiple resonant photon pair generation experiments, the photon pair generation was incessant within a range of 80 nm without missing teeth due to a mismatch of the energy conservation and the cavity resonance condition of the photons, resulting in over 1000-mode frequency multiplexed photon pairs in this range.},

keywords = {optical cavity},

pubstate = {published},

tppubtype = {article}

}

@article{Miki2019,

title = {Timing jitter characterization of the SFQ coincidence circuit by optically time-controlled signals from SSPDs},

author = {Shigehito Miki and Shigeyuki Miyajima and Masahiro Yabuno and Taro Yamashita and Takashi Yamamoto and Nobuyuki Imoto and Rikizo Ikuta and Robert Andrew Kirkwood and Robert Hadfield and Hirotaka Terai},

url = {https://ieeexplore.ieee.org/document/8675336},

doi = {10.1109/TASC.2019.2906258},

issn = {1051-8223},

year  = {2019},

date = {2019-03-27},

journal = {IEEE Transactions on Applied Superconductivity},

volume = {29},

number = {1302104},

keywords = {superconducting detector},

pubstate = {published},

tppubtype = {article}

}

@article{Yamamoto2019,

title = {Quantum Information Processing with Superconducting Nanowire Single-Photon Detectors},

author = {Takashi Yamamoto},

url = {http://search.ieice.org/bin/summary.php?id=e102-c_3_224\&category=C\&year=2019\&lang=E\&abst=},

doi = {10.1587/transele.2018SDI0002},

issn = {1745-1353},

year  = {2019},

date = {2019-03-01},

journal = {IEICE TRANS. ELECTRON.},

volume = {E102\textendashC},

number = {3},

pages = {pp.224-229},

keywords = {superconducting detector},

pubstate = {published},

tppubtype = {article}

}

@article{Hasegawa2019b,

title = {Experimental time-reversed adaptive Bell measurement towards all-photonic quantum repeaters},

author = {Yasushi Hasegawa and Rikizo Ikuta and Nobuyuki Matsuda and Kiyoshi Tamaki and Hoi-Kwong Lo and Takashi Yamamoto and Koji Azuma and Nobuyuki Imoto},

url = {https://www.nature.com/articles/s41467-018-08099-5},

doi = {10.1038/s41467-018-08099-5},

year  = {2019},

date = {2019-01-28},

journal = {Nature Communications},

volume = {10},

pages = {378},

keywords = {quantum repeater},

pubstate = {published},

tppubtype = {article}

}

@article{Hasegawa2019,

title = {Experimental time-reversed adaptive Bell measurement towards all-photonic quantum repeaters},

author = {Yasushi Hasegawa and Rikizo Ikuta and Nobuyuki Matsuda and Kiyoshi Tamaki and Hoi-Kwong Lo and Takashi Yamamoto and Koji Azuma and Nobuyuki Imoto},

url = {https://www.nature.com/articles/s41467-018-08099-5},

doi = {10.1038/s41467-018-08099-5},

year  = {2019},

date = {2019-01-28},

journal = {Nature Communications},

volume = {10},

pages = {378},

keywords = {quantum repeater},

pubstate = {published},

tppubtype = {article}

}

@article{Mizutani2019b,

title = {Quantum key distribution with setting-choice-independently correlated light sources},

author = {Akihiro Mizutani and Go Kato and Koji Azuma and Marcos Curty and Rikizo Ikuta and Takashi Yamamoto and Nobuyuki Imoto and Hoi-Kwong Lo and Kiyoshi Tamaki},

url = {https://www.nature.com/articles/s41534-018-0122-y},

doi = {10.1038/s41534-018-0122-y},

year  = {2019},

date = {2019-01-23},

journal = {npj Quantum Information},

volume = {5},

pages = {8},

keywords = {quantum cryptography},

pubstate = {published},

tppubtype = {article}

}

@article{Mizutani2019,

title = {Quantum key distribution with setting-choice-independently correlated light sources},

author = {Akihiro Mizutani and Go Kato and Koji Azuma and Marcos Curty and Rikizo Ikuta and Takashi Yamamoto and Nobuyuki Imoto and Hoi-Kwong Lo and Kiyoshi Tamaki},

url = {https://www.nature.com/articles/s41534-018-0122-y},

doi = {10.1038/s41534-018-0122-y},

year  = {2019},

date = {2019-01-23},

journal = {npj Quantum Information},

volume = {5},

pages = {8},

keywords = {quantum cryptography},

pubstate = {published},

tppubtype = {article}

}

@article{Miki2018b,

title = {Superconducting coincidence photon detector with short timing jitter},

author = {S Miki and S Miyajima and M Yabuno and T Yamashita and T Yamamoto and N Imoto and R Ikuta and R A Kirkwood and R H Hadfield and H Terai},

url = {https://aip.scitation.org/doi/10.1063/1.5037254},

doi = {10.1063/1.5037254},

year  = {2018},

date = {2018-06-26},

journal = {Appl. Phys. Lett.},

volume = {112},

pages = {262601},

keywords = {superconducting detector},

pubstate = {published},

tppubtype = {article}

}

@article{Miki2018,

title = {Superconducting coincidence photon detector with short timing jitter},

author = {S Miki and S Miyajima and M Yabuno and T Yamashita and T Yamamoto and N Imoto and R Ikuta and R A Kirkwood and R H Hadfield and H Terai},

url = {https://aip.scitation.org/doi/10.1063/1.5037254},

doi = {10.1063/1.5037254},

year  = {2018},

date = {2018-06-26},

journal = {Appl. Phys. Lett.},

volume = {112},

pages = {262601},

keywords = {superconducting detector},

pubstate = {published},

tppubtype = {article}

}

@article{Ikuta2018bc,

title = {Frequency comb generation in a quadratic nonlinear waveguide resonator},

author = {Rikizo Ikuta and Motoki Asano and Ryoya Tani and Takashi Yamamoto and Nobuyuki Imoto},

url = {https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-12-15551},

doi = {10.1364/OE.26.015551},

year  = {2018},

date = {2018-06-06},

journal = {Optics Express},

volume = {26},

number = {12},

pages = {15551--15558},

keywords = {optical cavity},

pubstate = {published},

tppubtype = {article}

}

@article{Ikuta2018b,

title = {Frequency comb generation in a quadratic nonlinear waveguide resonator},

author = {Rikizo Ikuta and Motoki Asano and Ryoya Tani and Takashi Yamamoto and Nobuyuki Imoto},

url = {https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-12-15551},

doi = {10.1364/OE.26.015551},

year  = {2018},

date = {2018-06-06},

journal = {Optics Express},

volume = {26},

number = {12},

pages = {15551--15558},

keywords = {optical cavity},

pubstate = {published},

tppubtype = {article}

}

@article{Ikuta2018d,

title = {Polarization insensitive frequency conversion for an atom-photon entanglement distribution via a telecom network},

author = {Rikizo Ikuta and Toshiki Kobayashi and Tetsuo Kawakami and Shigehito Miki and Masahiro Yabuno and Taro Yamashita and Hirotaka Terai and Masato Koashi and Tetsuya Mukai and Takashi Yamamoto and Nobuyuki Imoto},

url = {https://www.nature.com/articles/s41467-018-04338-x},

doi = {10.1038/s41467-018-04338-x},

year  = {2018},

date = {2018-05-21},

journal = {Nature Communications},

volume = {9},

pages = {1997},

keywords = {atom, quantum frequency conversion},

pubstate = {published},

tppubtype = {article}

}

@article{Ikuta2018b,

title = {Polarization insensitive frequency conversion for an atom-photon entanglement distribution via a telecom network},

author = {Rikizo Ikuta and Toshiki Kobayashi and Tetsuo Kawakami and Shigehito Miki and Masahiro Yabuno and Taro Yamashita and Hirotaka Terai and Masato Koashi and Tetsuya Mukai and Takashi Yamamoto and Nobuyuki Imoto},

url = {https://www.nature.com/articles/s41467-018-04338-x},

doi = {10.1038/s41467-018-04338-x},

year  = {2018},

date = {2018-05-21},

journal = {Nature Communications},

volume = {9},

pages = {1997},

keywords = {atom, quantum frequency conversion},

pubstate = {published},

tppubtype = {article}

}

@article{Walker2018b,

title = {Long-Distance Single Photon Transmission from a Trapped Ion via Quantum Frequency Conversion},

author = {Thomas Walker and Koichiro Miyanishi and Rikizo Ikuta and Hiroki Takahashi and Samir Vartabi Kashanian and Yoshiaki Tsujimoto and Kazuhiro Hayasaka and Takashi Yamamoto and Nobuyuki Imoto and Matthias Keller},

url = {https://doi.org/10.1103/PhysRevLett.120.203601 

https://doi.org/10.1103/PhysRevLett.120.203601},

doi = {10.1103/PhysRevLett.120.203601},

year  = {2018},

date = {2018-05-15},

journal = {Phys. Rev. Lett.},

volume = {120},

pages = {203601},

publisher = {American Physical Society},

keywords = {atom, quantum frequency conversion},

pubstate = {published},

tppubtype = {article}

}

@article{Asano2018b,

title = {An opto-electro-mechanical system based on evanescently-coupled optical microbottle and electromechanical resonator},

author = {Motoki Asano and Ryuichi Ohta and Takashi Yamamoto and Hajime Okamoto and Hiroshi Yamaguchi},

url = {https://doi.org/10.1063/1.5022115},

doi = {10.1063/1.5022115},

year  = {2018},

date = {2018-05-15},

journal = {Appl. Phys. Lett.},

volume = {112},

pages = {201103},

keywords = {optical cavity, optomechanics},

pubstate = {published},

tppubtype = {article}

}

@article{Walker2018,

title = {Long-Distance Single Photon Transmission from a Trapped Ion via Quantum Frequency Conversion},

author = {Thomas Walker and Koichiro Miyanishi and Rikizo Ikuta and Hiroki Takahashi and Samir Vartabi Kashanian and Yoshiaki Tsujimoto and Kazuhiro Hayasaka and Takashi Yamamoto and Nobuyuki Imoto and Matthias Keller},

url = {https://doi.org/10.1103/PhysRevLett.120.203601 

https://doi.org/10.1103/PhysRevLett.120.203601},

doi = {10.1103/PhysRevLett.120.203601},

year  = {2018},

date = {2018-05-15},

journal = {Phys. Rev. Lett.},

volume = {120},

pages = {203601},

publisher = {American Physical Society},

keywords = {atom, quantum frequency conversion},

pubstate = {published},

tppubtype = {article}

}

@article{Asano2018,

title = {An opto-electro-mechanical system based on evanescently-coupled optical microbottle and electromechanical resonator},

author = {Motoki Asano and Ryuichi Ohta and Takashi Yamamoto and Hajime Okamoto and Hiroshi Yamaguchi},

url = {https://doi.org/10.1063/1.5022115},

doi = {10.1063/1.5022115},

year  = {2018},

date = {2018-05-15},

journal = {Appl. Phys. Lett.},

volume = {112},

pages = {201103},

keywords = {optical cavity, optomechanics},

pubstate = {published},

tppubtype = {article}

}

@article{Uriri2018b,

title = {Active control of a plasmonic metamaterial for quantum state engineering},

author = {S A Uriri and T Tashima and X Zhang and M Asano and M Bechu and D \"{O} G\"{u}ney and T Yamamoto and \c{S} K \"{O}zdemir and M Wegener and M S Tame},

url = {https://doi.org/10.1103/PhysRevA.97.053810},

doi = {10.1103/PhysRevA.97.053810},

year  = {2018},

date = {2018-05-08},

journal = {Phys. Rev. A},

volume = {97},

pages = {053810},

keywords = {metamaterial},

pubstate = {published},

tppubtype = {article}

}

@article{Uriri2018,

title = {Active control of a plasmonic metamaterial for quantum state engineering},

author = {S A Uriri and T Tashima and X Zhang and M Asano and M Bechu and D \"{O} G\"{u}ney and T Yamamoto and \c{S} K \"{O}zdemir and M Wegener and M S Tame},

url = {https://doi.org/10.1103/PhysRevA.97.053810},

doi = {10.1103/PhysRevA.97.053810},

year  = {2018},

date = {2018-05-08},

journal = {Phys. Rev. A},

volume = {97},

pages = {053810},

keywords = {metamaterial},

pubstate = {published},

tppubtype = {article}

}

@article{tsujimoto2018highb,

title = {High-fidelity entanglement swapping and generation of three-qubit GHZ state using asynchronous telecom photon pair sources},

author = {Yoshiaki Tsujimoto and Motoki Tanaka and Nobuo Iwasaki and Rikizo Ikuta and Shigehito Miki and Taro Yamashita and Hirotaka Terai and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

doi = {10.1038/s41598-018-19738-8},

year  = {2018},

date = {2018-01-23},

journal = {Scientific reports},

volume = {8},

number = {1},

pages = {1446},

publisher = {Nature Publishing Group},

keywords = {multi-photon interference},

pubstate = {published},

tppubtype = {article}

}

@article{tsujimoto2018high,

title = {High-fidelity entanglement swapping and generation of three-qubit GHZ state using asynchronous telecom photon pair sources},

author = {Yoshiaki Tsujimoto and Motoki Tanaka and Nobuo Iwasaki and Rikizo Ikuta and Shigehito Miki and Taro Yamashita and Hirotaka Terai and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

doi = {10.1038/s41598-018-19738-8},

year  = {2018},

date = {2018-01-23},

journal = {Scientific reports},

volume = {8},

number = {1},

pages = {1446},

publisher = {Nature Publishing Group},

keywords = {multi-photon interference},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.97.012112b,

title = {Quantum weak and modular values in enlarged Hilbert spaces},

author = {Le Bin Ho and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.97.012112},

doi = {10.1103/PhysRevA.97.012112},

year  = {2018},

date = {2018-01-01},

journal = {Phys. Rev. A},

volume = {97},

pages = {012112},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.97.012112,

title = {Quantum weak and modular values in enlarged Hilbert spaces},

author = {Le Bin Ho and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.97.012112},

doi = {10.1103/PhysRevA.97.012112},

year  = {2018},

date = {2018-01-01},

journal = {Phys. Rev. A},

volume = {97},

pages = {012112},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.96.062321b,

title = {Verification of hypergraph states},

author = {Tomoyuki Morimae and Yuki Takeuchi and Masahito Hayashi},

url = {https://link.aps.org/doi/10.1103/PhysRevA.96.062321},

doi = {10.1103/PhysRevA.96.062321},

year  = {2017},

date = {2017-12-01},

journal = {Phys. Rev. A},

volume = {96},

pages = {062321},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.96.062321,

title = {Verification of hypergraph states},

author = {Tomoyuki Morimae and Yuki Takeuchi and Masahito Hayashi},

url = {https://link.aps.org/doi/10.1103/PhysRevA.96.062321},

doi = {10.1103/PhysRevA.96.062321},

year  = {2017},

date = {2017-12-01},

journal = {Phys. Rev. A},

volume = {96},

pages = {062321},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2058-9565-3-1-014002b,

title = {Security of quantum key distribution with iterative sifting},

author = {Kiyoshi Tamaki and Hoi-Kwong Lo and Akihiro Mizutani and Go Kato and Charles Ci Wen Lim and Koji Azuma and Marcos Curty},

url = {http://stacks.iop.org/2058-9565/3/i=1/a=014002},

year  = {2017},

date = {2017-10-01},

journal = {Quantum Science and Technology},

volume = {3},

number = {1},

pages = {014002},

abstract = {Several quantum key distribution (QKD) protocols employ iterative sifting. After each quantum transmission round, Alice and Bob disclose part of their setting information (including their basis choices) for the detected signals. This quantum phase then ends when the basis dependent termination conditions are met, i.e., the numbers of detected signals per basis exceed certain pre-agreed threshold values. Recently, however, Pfister et al (2016 New J. Phys. 18 053001) showed that the basis dependent termination condition makes QKD insecure, especially in the finite key regime, and they suggested to disclose all the setting information after finishing the quantum phase. However, this protocol has two main drawbacks: it requires that Alice possesses a large memory, and she also needs to have some a priori knowledge about the transmission rate of the quantum channel. Here we solve these two problems by introducing a basis-independent termination condition to the iterative sifting in the finite key regime. The use of this condition, in combination with Azuma’s inequality, provides a precise estimation on the amount of privacy amplification that needs to be applied, thus leading to the security of QKD protocols, including the loss-tolerant protocol (Tamaki et al 2014 Phys. Rev. A 90 052314), with iterative sifting. Our analysis indicates that to announce the basis information after each quantum transmission round does not compromise the key generation rate of the loss-tolerant protocol. Our result allows the implementation of wider classes of classical post-processing techniques in QKD with quantified security.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2058-9565-3-1-014003b,

title = {Information-theoretic security proof of differential-phase-shift quantum key distribution protocol based on complementarity},

author = {Akihiro Mizutani and Toshihiko Sasaki and Go Kato and Yuki Takeuchi and Kiyoshi Tamaki},

url = {http://stacks.iop.org/2058-9565/3/i=1/a=014003},

year  = {2017},

date = {2017-10-01},

journal = {Quantum Science and Technology},

volume = {3},

number = {1},

pages = {014003},

abstract = {We prove the information-theoretic security of the differential-phase-shift (DPS) quantum key distribution (QKD) protocol in the asymptotic regime based on the complementarity approach (arXiv:0704.3661 (2007)). Our security proof provides a slightly better key generation rate compared to the one derived in the previous security proof in (arXiv:1208.1995 (2012)) that is based on the Shor\textendashPreskill approach (Shor and Preskill 2000 Phys. Rev. Lett. 85 441). This improvement is obtained because the complementarity approach can employ more detailed information on Alice’s sending state in estimating the leaked information to an eavesdropper. Moreover, we remove the necessity of the numerical calculation that was needed in the previous analysis to estimate the leaked information. This leads to an advantage that our security proof enables us to evaluate the security of the DPS protocol with any block size. This paper highlights one of the fundamental differences between the Shor\textendashPreskill and the complementarity approaches.},

keywords = {quantum cryptography},

pubstate = {published},

tppubtype = {article}

}

@article{2058-9565-3-1-014002,

title = {Security of quantum key distribution with iterative sifting},

author = {Kiyoshi Tamaki and Hoi-Kwong Lo and Akihiro Mizutani and Go Kato and Charles Ci Wen Lim and Koji Azuma and Marcos Curty},

url = {http://stacks.iop.org/2058-9565/3/i=1/a=014002},

year  = {2017},

date = {2017-10-01},

journal = {Quantum Science and Technology},

volume = {3},

number = {1},

pages = {014002},

abstract = {Several quantum key distribution (QKD) protocols employ iterative sifting. After each quantum transmission round, Alice and Bob disclose part of their setting information (including their basis choices) for the detected signals. This quantum phase then ends when the basis dependent termination conditions are met, i.e., the numbers of detected signals per basis exceed certain pre-agreed threshold values. Recently, however, Pfister et al (2016 New J. Phys. 18 053001) showed that the basis dependent termination condition makes QKD insecure, especially in the finite key regime, and they suggested to disclose all the setting information after finishing the quantum phase. However, this protocol has two main drawbacks: it requires that Alice possesses a large memory, and she also needs to have some a priori knowledge about the transmission rate of the quantum channel. Here we solve these two problems by introducing a basis-independent termination condition to the iterative sifting in the finite key regime. The use of this condition, in combination with Azuma’s inequality, provides a precise estimation on the amount of privacy amplification that needs to be applied, thus leading to the security of QKD protocols, including the loss-tolerant protocol (Tamaki et al 2014 Phys. Rev. A 90 052314), with iterative sifting. Our analysis indicates that to announce the basis information after each quantum transmission round does not compromise the key generation rate of the loss-tolerant protocol. Our result allows the implementation of wider classes of classical post-processing techniques in QKD with quantified security.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{2058-9565-3-1-014003,

title = {Information-theoretic security proof of differential-phase-shift quantum key distribution protocol based on complementarity},

author = {Akihiro Mizutani and Toshihiko Sasaki and Go Kato and Yuki Takeuchi and Kiyoshi Tamaki},

url = {http://stacks.iop.org/2058-9565/3/i=1/a=014003},

year  = {2017},

date = {2017-10-01},

journal = {Quantum Science and Technology},

volume = {3},

number = {1},

pages = {014003},

abstract = {We prove the information-theoretic security of the differential-phase-shift (DPS) quantum key distribution (QKD) protocol in the asymptotic regime based on the complementarity approach (arXiv:0704.3661 (2007)). Our security proof provides a slightly better key generation rate compared to the one derived in the previous security proof in (arXiv:1208.1995 (2012)) that is based on the Shor\textendashPreskill approach (Shor and Preskill 2000 Phys. Rev. Lett. 85 441). This improvement is obtained because the complementarity approach can employ more detailed information on Alice’s sending state in estimating the leaked information to an eavesdropper. Moreover, we remove the necessity of the numerical calculation that was needed in the previous analysis to estimate the leaked information. This leads to an advantage that our security proof enables us to evaluate the security of the DPS protocol with any block size. This paper highlights one of the fundamental differences between the Shor\textendashPreskill and the complementarity approaches.},

keywords = {quantum cryptography},

pubstate = {published},

tppubtype = {article}

}

@article{Tsujimoto:17,

title = {High visibility Hong-Ou-Mandel interference via a time-resolved coincidence measurement},

author = {Yoshiaki Tsujimoto and Yukihiro Sugiura and Motoki Tanaka and Rikizo Ikuta and Shigehito Miki and Taro Yamashita and Hirotaka Terai and Mikio Fujiwara and Takashi Yamamoto and Masato Koashi and Masahide Sasaki and Nobuyuki Imoto},

url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-25-11-12069},

doi = {10.1364/OE.25.012069},

year  = {2017},

date = {2017-05-01},

journal = {Opt. Express},

volume = {25},

number = {11},

pages = {12069--12080},

publisher = {OSA},

abstract = {A high visibility Hong-Ou-Mandel (HOM) interference between two independently prepared photons plays an important role in various photonic quantum information processing. In a standard HOM experiment using photons generated by pulse-pumped spontaneous parametric down conversion (SPDC), larger detection time windows than the coherence time of photons have been employed for measuring the HOM visibility and/or drawing the HOM dip. If large amounts of stray photons continuously exist within the detection time windows, employing small detection time windows is favorable for reducing the effect of background noises. Especially, such a setup is helpful for the HOM experiment using continuous wave (cw)-pumped SPDC and the time-resolved coincidence measurement. Here we argue that the method for determining the HOM visibility used in the previous cw experiments tends to suffer from distortion arising from biased contribution of the background noises. We then present a new method with unbiased treatment of the cw backgrounds. By using this method, we experimentally demonstrate a high visibility HOM interference of two heralded telecom photons independently generated by SPDC with employing cw pump light. An observed HOM visibility is 0.87 \± 0.04, which is as high as those observed by using pulse-pumped SPDC photons.},

keywords = {multi-photon interference},

pubstate = {published},

tppubtype = {article}

}

@article{ikuta2017experimental,

title = {Experimental demonstration of robust entanglement distribution over reciprocal noisy channels assisted by a counter-propagating classical reference light},

author = {Rikizo Ikuta and Shota Nozaki and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

doi = {10.1038/s41598-017-05008-6},

year  = {2017},

date = {2017-05-01},

journal = {Scientific Reports},

volume = {7},

number = {1},

pages = {4819},

publisher = {Nature Publishing Group},

keywords = {multi-photon interference},

pubstate = {published},

tppubtype = {article}

}

@article{Kobayashi:17b,

title = {Mach-Zehnder interferometer using frequency-domain beamsplitter},

author = {Toshiki Kobayashi and Daisuke Yamazaki and Kenichiro Matsuki and Rikizo Ikuta and Shigehito Miki and Taro Yamashita and Hirotaka Terai and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-25-10-12052},

doi = {10.1364/OE.25.012052},

year  = {2017},

date = {2017-05-01},

journal = {Opt. Express},

volume = {25},

number = {10},

pages = {12052--12060},

publisher = {OSA},

abstract = {We demonstrate a first-order interference between coherent light at 1580 nm and 795 nm by using a frequency-domain Mach-Zehnder interferometer (MZI). The MZI is implemented by two frequency-domain BSs based on a second-order nonlinear optical effect in a periodically-poled lithium niobate waveguide with a strong pump light. The observed visibility is over 0.99 at 50\% conversion efficiencies of the BSs. Toward photonic quantum information processing, sufficiently small background photon rate is necessary. From measurement results with a superconducting single photon detector (SSPD), we discuss the feasibility of the frequency-domain MZI in a quantum regime. Our estimation shows that the single photon interference with the visibility above 0.9 is feasible with practical settings.},

keywords = {quantum frequency conversion},

pubstate = {published},

tppubtype = {article}

}

@article{Tsujimoto:17b,

title = {High visibility Hong-Ou-Mandel interference via a time-resolved coincidence measurement},

author = {Yoshiaki Tsujimoto and Yukihiro Sugiura and Motoki Tanaka and Rikizo Ikuta and Shigehito Miki and Taro Yamashita and Hirotaka Terai and Mikio Fujiwara and Takashi Yamamoto and Masato Koashi and Masahide Sasaki and Nobuyuki Imoto},

url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-25-11-12069},

doi = {10.1364/OE.25.012069},

year  = {2017},

date = {2017-05-01},

journal = {Opt. Express},

volume = {25},

number = {11},

pages = {12069--12080},

publisher = {OSA},

abstract = {A high visibility Hong-Ou-Mandel (HOM) interference between two independently prepared photons plays an important role in various photonic quantum information processing. In a standard HOM experiment using photons generated by pulse-pumped spontaneous parametric down conversion (SPDC), larger detection time windows than the coherence time of photons have been employed for measuring the HOM visibility and/or drawing the HOM dip. If large amounts of stray photons continuously exist within the detection time windows, employing small detection time windows is favorable for reducing the effect of background noises. Especially, such a setup is helpful for the HOM experiment using continuous wave (cw)-pumped SPDC and the time-resolved coincidence measurement. Here we argue that the method for determining the HOM visibility used in the previous cw experiments tends to suffer from distortion arising from biased contribution of the background noises. We then present a new method with unbiased treatment of the cw backgrounds. By using this method, we experimentally demonstrate a high visibility HOM interference of two heralded telecom photons independently generated by SPDC with employing cw pump light. An observed HOM visibility is 0.87 \± 0.04, which is as high as those observed by using pulse-pumped SPDC photons.},

keywords = {multi-photon interference},

pubstate = {published},

tppubtype = {article}

}

@article{Kobayashi:17,

title = {Mach-Zehnder interferometer using frequency-domain beamsplitter},

author = {Toshiki Kobayashi and Daisuke Yamazaki and Kenichiro Matsuki and Rikizo Ikuta and Shigehito Miki and Taro Yamashita and Hirotaka Terai and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-25-10-12052},

doi = {10.1364/OE.25.012052},

year  = {2017},

date = {2017-05-01},

journal = {Opt. Express},

volume = {25},

number = {10},

pages = {12052--12060},

publisher = {OSA},

abstract = {We demonstrate a first-order interference between coherent light at 1580 nm and 795 nm by using a frequency-domain Mach-Zehnder interferometer (MZI). The MZI is implemented by two frequency-domain BSs based on a second-order nonlinear optical effect in a periodically-poled lithium niobate waveguide with a strong pump light. The observed visibility is over 0.99 at 50\% conversion efficiencies of the BSs. Toward photonic quantum information processing, sufficiently small background photon rate is necessary. From measurement results with a superconducting single photon detector (SSPD), we discuss the feasibility of the frequency-domain MZI in a quantum regime. Our estimation shows that the single photon interference with the visibility above 0.9 is feasible with practical settings.},

keywords = {quantum frequency conversion},

pubstate = {published},

tppubtype = {article}

}

@article{ikuta2017experimentalb,

title = {Experimental demonstration of robust entanglement distribution over reciprocal noisy channels assisted by a counter-propagating classical reference light},

author = {Rikizo Ikuta and Shota Nozaki and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

doi = {10.1038/s41598-017-05008-6},

year  = {2017},

date = {2017-05-01},

journal = {Scientific Reports},

volume = {7},

number = {1},

pages = {4819},

publisher = {Nature Publishing Group},

keywords = {multi-photon interference},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.95.042301b,

title = {Differential-phase-shift quantum-key-distribution protocol with a small number of random delays},

author = {Yuki Hatakeyama and Akihiro Mizutani and Go Kato and Nobuyuki Imoto and Kiyoshi Tamaki},

url = {https://link.aps.org/doi/10.1103/PhysRevA.95.042301},

doi = {10.1103/PhysRevA.95.042301},

year  = {2017},

date = {2017-04-01},

journal = {Phys. Rev. A},

volume = {95},

pages = {042301},

publisher = {American Physical Society},

keywords = {quantum cryptography},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.95.042301,

title = {Differential-phase-shift quantum-key-distribution protocol with a small number of random delays},

author = {Yuki Hatakeyama and Akihiro Mizutani and Go Kato and Nobuyuki Imoto and Kiyoshi Tamaki},

url = {https://link.aps.org/doi/10.1103/PhysRevA.95.042301},

doi = {10.1103/PhysRevA.95.042301},

year  = {2017},

date = {2017-04-01},

journal = {Phys. Rev. A},

volume = {95},

pages = {042301},

publisher = {American Physical Society},

keywords = {quantum cryptography},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.95.032135b,

title = {Generalized modular-value-based scheme and its generalized modular value},

author = {Le Bin Ho and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.95.032135},

doi = {10.1103/PhysRevA.95.032135},

year  = {2017},

date = {2017-03-01},

journal = {Phys. Rev. A},

volume = {95},

pages = {032135},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.95.032135,

title = {Generalized modular-value-based scheme and its generalized modular value},

author = {Le Bin Ho and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.95.032135},

doi = {10.1103/PhysRevA.95.032135},

year  = {2017},

date = {2017-03-01},

journal = {Phys. Rev. A},

volume = {95},

pages = {032135},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1367-2630-18-12-123002b,

title = {When a negative weak value −1 plays the counterpart of a probability 1},

author = {Kazuhiro Yokota and Nobuyuki Imoto},

url = {http://stacks.iop.org/1367-2630/18/i=12/a=123002},

year  = {2016},

date = {2016-12-01},

journal = {New Journal of Physics},

volume = {18},

number = {12},

pages = {123002},

abstract = {When the weak value of a projector is 1, a quantum system behaves as in that eigenstate with probability 1. By definition, however, the weak value may take an anomalous value lying outside the range of probability like −1. From the viewpoint of a physical effect, we show that such a negative weak value of −1 can be regarded as the counterpart of the ordinary value of 1. Using photons, we experimentally verify it as the symmetrical shift in polarization depending on the weak value given by pre-postselection of the path state. Unlike observation of a weak value as an ensemble average via weak measurements, the effect of a weak value is definitely confirmed in Hong\textendashOu\textendashMandel effect: the symmetrical shift corresponding to the weak value can be directly observed as the rotation angle of a half wave plate.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Asano:16bc,

title = {Visible light emission from a silica microbottle resonator by second- and third-harmonic generation},

author = {Motoki Asano and Shoichi Komori and Rikizo Ikuta and Nobuyuki Imoto and \c{S} and Takashi Yamamoto},

url = {http://ol.osa.org/abstract.cfm?URI=ol-41-24-5793},

doi = {10.1364/OL.41.005793},

year  = {2016},

date = {2016-12-01},

journal = {Opt. Lett.},

volume = {41},

number = {24},

pages = {5793--5796},

publisher = {OSA},

abstract = {We report the first observation of nonlinear harmonic generation and sum frequency generation (SFG) coupled with stimulated Raman scattering (SRS) via the second-order (\χ(2)) and the third-order (\χ(3)) nonlinearities in a silica microbottle resonator. The visible light emission due to third-harmonic generation (THG) was observed in both the output of a tapered fiber and the optical microscope images, which can be used to identify the axial mode profiles. SFG enabled by three- and four-wave mixing processes between the pump light and the light generated via SRS was also observed. Second-harmonic generation (SHG) and the SFG are enabled by \χ(2) induced in silica by surface effects and multipole excitations.},

keywords = {optical cavity},

pubstate = {published},

tppubtype = {article}

}

@article{1367-2630-18-12-123002,

title = {When a negative weak value −1 plays the counterpart of a probability 1},

author = {Kazuhiro Yokota and Nobuyuki Imoto},

url = {http://stacks.iop.org/1367-2630/18/i=12/a=123002},

year  = {2016},

date = {2016-12-01},

journal = {New Journal of Physics},

volume = {18},

number = {12},

pages = {123002},

abstract = {When the weak value of a projector is 1, a quantum system behaves as in that eigenstate with probability 1. By definition, however, the weak value may take an anomalous value lying outside the range of probability like −1. From the viewpoint of a physical effect, we show that such a negative weak value of −1 can be regarded as the counterpart of the ordinary value of 1. Using photons, we experimentally verify it as the symmetrical shift in polarization depending on the weak value given by pre-postselection of the path state. Unlike observation of a weak value as an ensemble average via weak measurements, the effect of a weak value is definitely confirmed in Hong\textendashOu\textendashMandel effect: the symmetrical shift corresponding to the weak value can be directly observed as the rotation angle of a half wave plate.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.94.062336b,

title = {Ancilla-driven instantaneous quantum polynomial time circuit for quantum supremacy},

author = {Yuki Takeuchi and Yasuhiro Takahashi},

url = {https://link.aps.org/doi/10.1103/PhysRevA.94.062336},

doi = {10.1103/PhysRevA.94.062336},

year  = {2016},

date = {2016-12-01},

journal = {Phys. Rev. A},

volume = {94},

pages = {062336},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Asano:16b,

title = {Visible light emission from a silica microbottle resonator by second- and third-harmonic generation},

author = {Motoki Asano and Shoichi Komori and Rikizo Ikuta and Nobuyuki Imoto and \c{S} and Takashi Yamamoto},

url = {http://ol.osa.org/abstract.cfm?URI=ol-41-24-5793},

doi = {10.1364/OL.41.005793},

year  = {2016},

date = {2016-12-01},

journal = {Opt. Lett.},

volume = {41},

number = {24},

pages = {5793--5796},

publisher = {OSA},

abstract = {We report the first observation of nonlinear harmonic generation and sum frequency generation (SFG) coupled with stimulated Raman scattering (SRS) via the second-order (\χ(2)) and the third-order (\χ(3)) nonlinearities in a silica microbottle resonator. The visible light emission due to third-harmonic generation (THG) was observed in both the output of a tapered fiber and the optical microscope images, which can be used to identify the axial mode profiles. SFG enabled by three- and four-wave mixing processes between the pump light and the light generated via SRS was also observed. Second-harmonic generation (SHG) and the SFG are enabled by \χ(2) induced in silica by surface effects and multipole excitations.},

keywords = {optical cavity},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.94.062336,

title = {Ancilla-driven instantaneous quantum polynomial time circuit for quantum supremacy},

author = {Yuki Takeuchi and Yasuhiro Takahashi},

url = {https://link.aps.org/doi/10.1103/PhysRevA.94.062336},

doi = {10.1103/PhysRevA.94.062336},

year  = {2016},

date = {2016-12-01},

journal = {Phys. Rev. A},

volume = {94},

pages = {062336},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ikuta:16b,

title = {Heralded single excitation of atomic ensemble via solid-state-based telecom photon detection},

author = {Rikizo Ikuta and Toshiki Kobayashi and Kenichiro Matsuki and Shigehito Miki and Taro Yamashita and Hirotaka Terai and Takashi Yamamoto and Masato Koashi and Tetsuya Mukai and Nobuyuki Imoto},

url = {http://www.osapublishing.org/optica/abstract.cfm?URI=optica-3-11-1279},

doi = {10.1364/OPTICA.3.001279},

year  = {2016},

date = {2016-11-01},

journal = {Optica},

volume = {3},

number = {11},

pages = {1279--1284},

publisher = {OSA},

abstract = {Telecom photonic quantum networks with matter quantum systems enable a rich variety of applications, such as long-distance quantum cryptography and one-way quantum computing. Preparation of a heralded single excitation (HSE) in an atomic ensemble by detecting a telecom wavelength photon having a correlation with the atomic excitation is an important step. Such a system has been demonstrated with a quantum frequency conversion (QFC) to telecom wavelength employing a Rb atomic cloud. However, the limited wavelength selection prevents the next step toward linking various kinds of matter quantum systems through long-distance fiber-based quantum communications. Here we for the first time, demonstrate HSE with a solid-state-based QFC and a detector for a telecom wavelength that will have the great advantage of the utility of mature telecom technologies. We unambiguously show that the demonstrated HSE indicates non-classical statistics by the direct measurement of the autocorrelation function.},

note = {press release by Osaka univ.},

keywords = {atom, quantum frequency conversion},

pubstate = {published},

tppubtype = {article}

}

@article{asano2016anomalousb,

title = {Anomalous time delays and quantum weak measurements in optical microresonators},

author = {Motoki Asano and Konstantin Y Bliokh and Yury P Bliokh and Abraham G Kofman and Rikizo Ikuta and Takashi Yamamoto and Yuri S Kivshar and Lan Yang and Nobuyuki Imoto and \c{S} and Franco Nori},

doi = {10.1038/ncomms13488},

year  = {2016},

date = {2016-11-01},

journal = {Nature communications},

volume = {7},

pages = {13488},

publisher = {Nature Publishing Group},

keywords = {optical cavity},

pubstate = {published},

tppubtype = {article}

}

@article{Ikuta:16,

title = {Heralded single excitation of atomic ensemble via solid-state-based telecom photon detection},

author = {Rikizo Ikuta and Toshiki Kobayashi and Kenichiro Matsuki and Shigehito Miki and Taro Yamashita and Hirotaka Terai and Takashi Yamamoto and Masato Koashi and Tetsuya Mukai and Nobuyuki Imoto},

url = {http://www.osapublishing.org/optica/abstract.cfm?URI=optica-3-11-1279},

doi = {10.1364/OPTICA.3.001279},

year  = {2016},

date = {2016-11-01},

journal = {Optica},

volume = {3},

number = {11},

pages = {1279--1284},

publisher = {OSA},

abstract = {Telecom photonic quantum networks with matter quantum systems enable a rich variety of applications, such as long-distance quantum cryptography and one-way quantum computing. Preparation of a heralded single excitation (HSE) in an atomic ensemble by detecting a telecom wavelength photon having a correlation with the atomic excitation is an important step. Such a system has been demonstrated with a quantum frequency conversion (QFC) to telecom wavelength employing a Rb atomic cloud. However, the limited wavelength selection prevents the next step toward linking various kinds of matter quantum systems through long-distance fiber-based quantum communications. Here we for the first time, demonstrate HSE with a solid-state-based QFC and a detector for a telecom wavelength that will have the great advantage of the utility of mature telecom technologies. We unambiguously show that the demonstrated HSE indicates non-classical statistics by the direct measurement of the autocorrelation function.},

note = {press release by Osaka univ.},

keywords = {atom, quantum frequency conversion},

pubstate = {published},

tppubtype = {article}

}

@article{azuma2016fundamentalb,

title = {Fundamental rate-loss trade-off for the quantum internet},

author = {Koji Azuma and Akihiro Mizutani and Hoi-Kwong Lo},

doi = {10.1038/ncomms13523},

year  = {2016},

date = {2016-11-01},

journal = {Nature communications},

volume = {7},

pages = {13523},

publisher = {Nature Publishing Group},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{asano2016anomalous,

title = {Anomalous time delays and quantum weak measurements in optical microresonators},

author = {Motoki Asano and Konstantin Y Bliokh and Yury P Bliokh and Abraham G Kofman and Rikizo Ikuta and Takashi Yamamoto and Yuri S Kivshar and Lan Yang and Nobuyuki Imoto and \c{S} and Franco Nori},

doi = {10.1038/ncomms13488},

year  = {2016},

date = {2016-11-01},

journal = {Nature communications},

volume = {7},

pages = {13488},

publisher = {Nature Publishing Group},

keywords = {optical cavity},

pubstate = {published},

tppubtype = {article}

}

@article{azuma2016fundamental,

title = {Fundamental rate-loss trade-off for the quantum internet},

author = {Koji Azuma and Akihiro Mizutani and Hoi-Kwong Lo},

doi = {10.1038/ncomms13523},

year  = {2016},

date = {2016-11-01},

journal = {Nature communications},

volume = {7},

pages = {13523},

publisher = {Nature Publishing Group},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevLett.117.173601b,

title = {Superradiant Phase Transition in a Superconducting Circuit in Thermal Equilibrium},

author = {Motoaki Bamba and Kunihiro Inomata and Yasunobu Nakamura},

url = {https://link.aps.org/doi/10.1103/PhysRevLett.117.173601},

doi = {10.1103/PhysRevLett.117.173601},

year  = {2016},

date = {2016-10-01},

journal = {Phys. Rev. Lett.},

volume = {117},

pages = {173601},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{yamashita2016superconductingb,

title = {Superconducting nanowire single-photon detectors with non-periodic dielectric multilayers},

author = {Taro Yamashita and Kentaro Waki and Shigehito Miki and Robert A Kirkwood and Robert H Hadfield and Hirotaka Terai},

doi = {10.1038/srep35240},

year  = {2016},

date = {2016-10-01},

journal = {Scientific reports},

volume = {6},

pages = {35240},

publisher = {Nature Publishing Group},

keywords = {superconducting detector},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevLett.117.173601,

title = {Superradiant Phase Transition in a Superconducting Circuit in Thermal Equilibrium},

author = {Motoaki Bamba and Kunihiro Inomata and Yasunobu Nakamura},

url = {https://link.aps.org/doi/10.1103/PhysRevLett.117.173601},

doi = {10.1103/PhysRevLett.117.173601},

year  = {2016},

date = {2016-10-01},

journal = {Phys. Rev. Lett.},

volume = {117},

pages = {173601},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{yamashita2016superconducting,

title = {Superconducting nanowire single-photon detectors with non-periodic dielectric multilayers},

author = {Taro Yamashita and Kentaro Waki and Shigehito Miki and Robert A Kirkwood and Robert H Hadfield and Hirotaka Terai},

doi = {10.1038/srep35240},

year  = {2016},

date = {2016-10-01},

journal = {Scientific reports},

volume = {6},

pages = {35240},

publisher = {Nature Publishing Group},

keywords = {superconducting detector},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.94.033802b,

title = {Maxwell boundary conditions imply non-Lindblad master equation},

author = {Motoaki Bamba and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.94.033802},

doi = {10.1103/PhysRevA.94.033802},

year  = {2016},

date = {2016-09-01},

journal = {Phys. Rev. A},

volume = {94},

pages = {033802},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.94.033802,

title = {Maxwell boundary conditions imply non-Lindblad master equation},

author = {Motoaki Bamba and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.94.033802},

doi = {10.1103/PhysRevA.94.033802},

year  = {2016},

date = {2016-09-01},

journal = {Phys. Rev. A},

volume = {94},

pages = {033802},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1002/2016RS006073b,

title = {Single‐ion spectroscopy system for the 2S1/2(F = 0) − 2D3/2(F = 2) transition in 171Yb+},

author = {Yasutaka Imai and Tatsuya Nishi and Masatoshi Nishizaki and Sho Kawajiri and Yuto Muroki and Rikizo Ikuta and Kai Matsumoto and Masao Kitano and Kazuhiko Sugiyama},

url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2016RS006073},

doi = {10.1002/2016RS006073},

year  = {2016},

date = {2016-08-01},

journal = {Radio Science},

volume = {51},

number = {8},

pages = {1385-1395},

abstract = {Abstract We report on our system and scheme for single‐ion spectroscopy of the clock transition in 171Yb+. Spectroscopy of the clock transition requires decoupling of the state from the laser cooling cycle. We investigate this decoupling of the state by using independent light sources for driving of all the transitions between the hyperfine structures contained in the cooling and repumping transitions. We observe the carrier spectrum of the magnetic‐insensitive transition with a spectral width of 380 Hz.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1002/2016RS006073,

title = {Single‐ion spectroscopy system for the 2S1/2(F = 0) − 2D3/2(F = 2) transition in 171Yb+},

author = {Yasutaka Imai and Tatsuya Nishi and Masatoshi Nishizaki and Sho Kawajiri and Yuto Muroki and Rikizo Ikuta and Kai Matsumoto and Masao Kitano and Kazuhiko Sugiyama},

url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2016RS006073},

doi = {10.1002/2016RS006073},

year  = {2016},

date = {2016-08-01},

journal = {Radio Science},

volume = {51},

number = {8},

pages = {1385-1395},

abstract = {Abstract We report on our system and scheme for single‐ion spectroscopy of the clock transition in 171Yb+. Spectroscopy of the clock transition requires decoupling of the state from the laser cooling cycle. We investigate this decoupling of the state by using independent light sources for driving of all the transitions between the hyperfine structures contained in the cooling and repumping transitions. We observe the carrier spectrum of the magnetic‐insensitive transition with a spectral width of 380 Hz.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1002/lpor.201500243b,

title = {Observation of optomechanical coupling in a microbottle resonator},

author = {Motoki Asano and Yuki Takeuchi and Weijian Chen and \c{S} and Rikizo Ikuta and Nobuyuki Imoto and Lan Yang and Takashi Yamamoto},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lpor.201500243},

doi = {10.1002/lpor.201500243},

year  = {2016},

date = {2016-07-01},

journal = {Laser \& Photonics Reviews},

volume = {10},

number = {4},

pages = {603-611},

abstract = {Abstract In this work, we report optomechanical coupling, resolved sidebands and phonon lasing in a solid‐core microbottle resonator fabricated on a single mode optical fiber. Mechanical modes with quality factors (Qm) as high as 1.57 × 104 and 1.45 × 104 were observed, respectively, at the mechanical frequencies and . The maximum  Hz is close to the theoretical lower bound of 6 × 1012 Hz needed to overcome thermal decoherence for resolved‐sideband cooling of mechanical motion at room temperature, suggesting microbottle resonators as a possible platform for this endeavor. In addition to optomechanical effects, scatter‐induced mode splitting and ringing phenomena, which are typical for high‐quality optical resonances, were also observed in a microbottle resonator.},

keywords = {optical cavity, optomechanics},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1002/lpor.201500243,

title = {Observation of optomechanical coupling in a microbottle resonator},

author = {Motoki Asano and Yuki Takeuchi and Weijian Chen and \c{S} and Rikizo Ikuta and Nobuyuki Imoto and Lan Yang and Takashi Yamamoto},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/lpor.201500243},

doi = {10.1002/lpor.201500243},

year  = {2016},

date = {2016-07-01},

journal = {Laser \& Photonics Reviews},

volume = {10},

number = {4},

pages = {603-611},

abstract = {Abstract In this work, we report optomechanical coupling, resolved sidebands and phonon lasing in a solid‐core microbottle resonator fabricated on a single mode optical fiber. Mechanical modes with quality factors (Qm) as high as 1.57 × 104 and 1.45 × 104 were observed, respectively, at the mechanical frequencies and . The maximum  Hz is close to the theoretical lower bound of 6 × 1012 Hz needed to overcome thermal decoherence for resolved‐sideband cooling of mechanical motion at room temperature, suggesting microbottle resonators as a possible platform for this endeavor. In addition to optomechanical effects, scatter‐induced mode splitting and ringing phenomena, which are typical for high‐quality optical resonances, were also observed in a microbottle resonator.},

keywords = {optical cavity, optomechanics},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.93.052307b,

title = {Blind quantum computation over a collective-noise channel},

author = {Yuki Takeuchi and Keisuke Fujii and Rikizo Ikuta and Takashi Yamamoto and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.93.052307},

doi = {10.1103/PhysRevA.93.052307},

year  = {2016},

date = {2016-05-01},

journal = {Phys. Rev. A},

volume = {93},

pages = {052307},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Asano:16d,

title = {Stimulated Brillouin scattering and Brillouin-coupled four-wave-mixing in a silica microbottle resonator},

author = {Motoki Asano and Yuki Takeuchi and \c{S} and Rikizo Ikuta and Lan Yang and Nobuyuki Imoto and Takashi Yamamoto},

url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-24-11-12082},

doi = {10.1364/OE.24.012082},

year  = {2016},

date = {2016-05-01},

journal = {Opt. Express},

volume = {24},

number = {11},

pages = {12082--12092},

publisher = {OSA},

abstract = {We report the first observation of stimulated Brillouin scattering (SBS) with Brillouin lasing, and Brillouin-coupled four-wave-mixing (FWM) in an ultra-high-Q silica microbottle resonator. The Brillouin lasing was observed at the frequency of \ΩB $=$ 2\π \× 10.4 GHz with a threshold power of 0.45 mW. Coupling between Brillouin and FWM was observed in both backward and forward scattering directions with separations of 2\ΩB. At a pump power of 10 mW, FWM spacing reached to 7th and 9th order anti-Stokes and Stokes, respectively.},

keywords = {optical cavity, optomechanics},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.93.052307,

title = {Blind quantum computation over a collective-noise channel},

author = {Yuki Takeuchi and Keisuke Fujii and Rikizo Ikuta and Takashi Yamamoto and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.93.052307},

doi = {10.1103/PhysRevA.93.052307},

year  = {2016},

date = {2016-05-01},

journal = {Phys. Rev. A},

volume = {93},

pages = {052307},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Asano:16b,

title = {Stimulated Brillouin scattering and Brillouin-coupled four-wave-mixing in a silica microbottle resonator},

author = {Motoki Asano and Yuki Takeuchi and \c{S} and Rikizo Ikuta and Lan Yang and Nobuyuki Imoto and Takashi Yamamoto},

url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-24-11-12082},

doi = {10.1364/OE.24.012082},

year  = {2016},

date = {2016-05-01},

journal = {Opt. Express},

volume = {24},

number = {11},

pages = {12082--12092},

publisher = {OSA},

abstract = {We report the first observation of stimulated Brillouin scattering (SBS) with Brillouin lasing, and Brillouin-coupled four-wave-mixing (FWM) in an ultra-high-Q silica microbottle resonator. The Brillouin lasing was observed at the frequency of \ΩB $=$ 2\π \× 10.4 GHz with a threshold power of 0.45 mW. Coupling between Brillouin and FWM was observed in both backward and forward scattering directions with separations of 2\ΩB. At a pump power of 10 mW, FWM spacing reached to 7th and 9th order anti-Stokes and Stokes, respectively.},

keywords = {optical cavity, optomechanics},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.93.042325b,

title = {Security of quantum key distribution with light sources that are not independently and identically distributed},

author = {Yuichi Nagamatsu and Akihiro Mizutani and Rikizo Ikuta and Takashi Yamamoto and Nobuyuki Imoto and Kiyoshi Tamaki},

url = {https://link.aps.org/doi/10.1103/PhysRevA.93.042325},

doi = {10.1103/PhysRevA.93.042325},

year  = {2016},

date = {2016-04-01},

journal = {Phys. Rev. A},

volume = {93},

pages = {042325},

publisher = {American Physical Society},

keywords = {quantum cryptography},

pubstate = {published},

tppubtype = {article}

}

@article{kobayashi2016frequencyb,

title = {Frequency-domain Hong-Ou-Mandel interference},

author = {Toshiki Kobayashi and Rikizo Ikuta and Shuto Yasui and Shigehito Miki and Taro Yamashita and Hirotaka Terai and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

url = {http://qi.mp.es.osaka-u.ac.jp/imotolab/index-j/activity/NP-2016/index.html 

https://www.nature.com/articles/nphoton.2016.74},

doi = {10.1038/nphoton.2016.74},

year  = {2016},

date = {2016-04-01},

journal = {Nature Photonics},

volume = {10},

number = {7},

pages = {441},

publisher = {Nature Publishing Group},

note = {press release by Osaka univ. (see "Links")},

keywords = {press, quantum frequency conversion},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.93.042325,

title = {Security of quantum key distribution with light sources that are not independently and identically distributed},

author = {Yuichi Nagamatsu and Akihiro Mizutani and Rikizo Ikuta and Takashi Yamamoto and Nobuyuki Imoto and Kiyoshi Tamaki},

url = {https://link.aps.org/doi/10.1103/PhysRevA.93.042325},

doi = {10.1103/PhysRevA.93.042325},

year  = {2016},

date = {2016-04-01},

journal = {Phys. Rev. A},

volume = {93},

pages = {042325},

publisher = {American Physical Society},

keywords = {quantum cryptography},

pubstate = {published},

tppubtype = {article}

}

@article{kobayashi2016frequency,

title = {Frequency-domain Hong-Ou-Mandel interference},

author = {Toshiki Kobayashi and Rikizo Ikuta and Shuto Yasui and Shigehito Miki and Taro Yamashita and Hirotaka Terai and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

url = {http://qi.mp.es.osaka-u.ac.jp/imotolab/index-j/activity/NP-2016/index.html 

https://www.nature.com/articles/nphoton.2016.74},

doi = {10.1038/nphoton.2016.74},

year  = {2016},

date = {2016-04-01},

journal = {Nature Photonics},

volume = {10},

number = {7},

pages = {441},

publisher = {Nature Publishing Group},

note = {press release by Osaka univ. (see "Links")},

keywords = {press, quantum frequency conversion},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1063/1.4948922b,

title = {Controlling slow and fast light and dynamic pulse-splitting with tunable optical gain in a whispering-gallery-mode microcavity},

author = {Motoki Asano and \c{S} and Weijian Chen and Rikizo Ikuta and Lan Yang and Nobuyuki Imoto and Takashi Yamamoto},

url = {https://doi.org/10.1063/1.4948922},

doi = {10.1063/1.4948922},

year  = {2016},

date = {2016-01-01},

journal = {Applied Physics Letters},

volume = {108},

number = {18},

pages = {181105},

keywords = {optical cavity},

pubstate = {published},

tppubtype = {article}

}

@article{HO20162129b,

title = {Full characterization of modular values for finite-dimensional systems},

author = {Le Bin Ho and Nobuyuki Imoto},

url = {http://www.sciencedirect.com/science/article/pii/S0375960116301773},

doi = {https://doi.org/10.1016/j.physleta.2016.05.005},

issn = {0375-9601},

year  = {2016},

date = {2016-01-01},

journal = {Physics Letters A},

volume = {380},

number = {25},

pages = {2129 - 2135},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1063/1.4948922,

title = {Controlling slow and fast light and dynamic pulse-splitting with tunable optical gain in a whispering-gallery-mode microcavity},

author = {Motoki Asano and \c{S} and Weijian Chen and Rikizo Ikuta and Lan Yang and Nobuyuki Imoto and Takashi Yamamoto},

url = {https://doi.org/10.1063/1.4948922},

doi = {10.1063/1.4948922},

year  = {2016},

date = {2016-01-01},

journal = {Applied Physics Letters},

volume = {108},

number = {18},

pages = {181105},

keywords = {optical cavity},

pubstate = {published},

tppubtype = {article}

}

@article{HO20162129,

title = {Full characterization of modular values for finite-dimensional systems},

author = {Le Bin Ho and Nobuyuki Imoto},

url = {http://www.sciencedirect.com/science/article/pii/S0375960116301773},

doi = {https://doi.org/10.1016/j.physleta.2016.05.005},

issn = {0375-9601},

year  = {2016},

date = {2016-01-01},

journal = {Physics Letters A},

volume = {380},

number = {25},

pages = {2129 - 2135},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{asano2015distillationb,

title = {Distillation of photon entanglement using a plasmonic metamaterial},

author = {Motoki Asano and Muriel Bechu and Mark Tame and \c{S} and Rikizo Ikuta and Durdu \"{O} G\"{u}ney and Takashi Yamamoto and Lan Yang and Martin Wegener and Nobuyuki Imoto},

doi = {10.1038/srep18313},

year  = {2015},

date = {2015-12-01},

journal = {Scientific reports},

volume = {5},

pages = {18313},

publisher = {Nature Publishing Group},

keywords = {entanglement, metamaterial},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.92.060303b,

title = {Robustness of the round-robin differential-phase-shift quantum-key-distribution protocol against source flaws},

author = {Akihiro Mizutani and Nobuyuki Imoto and Kiyoshi Tamaki},

url = {https://link.aps.org/doi/10.1103/PhysRevA.92.060303},

doi = {10.1103/PhysRevA.92.060303},

year  = {2015},

date = {2015-12-01},

journal = {Phys. Rev. A},

volume = {92},

pages = {060303},

publisher = {American Physical Society},

keywords = {quantum cryptography},

pubstate = {published},

tppubtype = {article}

}

@article{asano2015distillation,

title = {Distillation of photon entanglement using a plasmonic metamaterial},

author = {Motoki Asano and Muriel Bechu and Mark Tame and \c{S} and Rikizo Ikuta and Durdu \"{O} G\"{u}ney and Takashi Yamamoto and Lan Yang and Martin Wegener and Nobuyuki Imoto},

doi = {10.1038/srep18313},

year  = {2015},

date = {2015-12-01},

journal = {Scientific reports},

volume = {5},

pages = {18313},

publisher = {Nature Publishing Group},

keywords = {entanglement, metamaterial},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.92.060303,

title = {Robustness of the round-robin differential-phase-shift quantum-key-distribution protocol against source flaws},

author = {Akihiro Mizutani and Nobuyuki Imoto and Kiyoshi Tamaki},

url = {https://link.aps.org/doi/10.1103/PhysRevA.92.060303},

doi = {10.1103/PhysRevA.92.060303},

year  = {2015},

date = {2015-12-01},

journal = {Phys. Rev. A},

volume = {92},

pages = {060303},

publisher = {American Physical Society},

keywords = {quantum cryptography},

pubstate = {published},

tppubtype = {article}

}

@article{Asano:15b,

title = {Analytical investigation of optical vortices emitted from a collectively polarized dipole array},

author = {Motoki Asano and Tohru Takahashi},

url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-23-21-27998},

doi = {10.1364/OE.23.027998},

year  = {2015},

date = {2015-10-01},

journal = {Opt. Express},

volume = {23},

number = {21},

pages = {27998--28011},

publisher = {OSA},

abstract = {Many approaches for producing optical vortices have been developed both for fundamental interests of science and for engineering applications. In particular, the approach with direct excitation of several emitters has a potential to control the topological charges with a control of the source conditions without any modifications of structures of the system. In this paper, we investigate the propagation properties of the optical vortices emitted from a collectively polarized electric dipole array as a simple model of the several emitters. Using an analytical approach based on the Jacobi-Anger expansion, we derive a relationship between the topological charge of the optical vortices and the source conditions of the emitter, and clarify and report our new finding; there exists an intrinsic split of the singular points in the electric field due to the spin-orbit interaction of the dipole fields.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Asano:15,

title = {Analytical investigation of optical vortices emitted from a collectively polarized dipole array},

author = {Motoki Asano and Tohru Takahashi},

url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-23-21-27998},

doi = {10.1364/OE.23.027998},

year  = {2015},

date = {2015-10-01},

journal = {Opt. Express},

volume = {23},

number = {21},

pages = {27998--28011},

publisher = {OSA},

abstract = {Many approaches for producing optical vortices have been developed both for fundamental interests of science and for engineering applications. In particular, the approach with direct excitation of several emitters has a potential to control the topological charges with a control of the source conditions without any modifications of structures of the system. In this paper, we investigate the propagation properties of the optical vortices emitted from a collectively polarized electric dipole array as a simple model of the several emitters. Using an analytical approach based on the Jacobi-Anger expansion, we derive a relationship between the topological charge of the optical vortices and the source conditions of the emitter, and clarify and report our new finding; there exists an intrinsic split of the singular points in the electric field due to the spin-orbit interaction of the dipole fields.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1367-2630-17-9-093011b,

title = {Finite-key security analysis of quantum key distribution with imperfect light sources},

author = {Akihiro Mizutani and Marcos Curty and Charles Ci Wen Lim and Nobuyuki Imoto and Kiyoshi Tamaki},

url = {http://stacks.iop.org/1367-2630/17/i=9/a=093011},

year  = {2015},

date = {2015-09-01},

journal = {New Journal of Physics},

volume = {17},

number = {9},

pages = {093011},

abstract = {In recent years, the gap between theory and practice in quantum key distribution (QKD) has been significantly narrowed, particularly for QKD systems with arbitrarily flawed optical receivers. The status for QKD systems with imperfect light sources is however less satisfactory, in the sense that the resulting secure key rates are often overly dependent on the quality of state preparation. This is especially the case when the channel loss is high. Very recently, to overcome this limitation, Tamaki et al proposed a QKD protocol based on the so-called ‘rejected data analysis’, and showed that its security\textemdashin the limit of infinitely long keys\textemdashis almost independent of any encoding flaw in the qubit space, being this protocol compatible with the decoy state method. Here, as a step towards practical QKD, we show that a similar conclusion is reached in the finite-key regime, even when the intensity of the light source is unstable. More concretely, we derive security bounds for a wide class of realistic light sources and show that the bounds are also efficient in the presence of high channel loss. Our results strongly suggest the feasibility of long distance provably secure communication with imperfect light sources.},

keywords = {quantum cryptography},

pubstate = {published},

tppubtype = {article}

}

@article{1367-2630-17-9-093011,

title = {Finite-key security analysis of quantum key distribution with imperfect light sources},

author = {Akihiro Mizutani and Marcos Curty and Charles Ci Wen Lim and Nobuyuki Imoto and Kiyoshi Tamaki},

url = {http://stacks.iop.org/1367-2630/17/i=9/a=093011},

year  = {2015},

date = {2015-09-01},

journal = {New Journal of Physics},

volume = {17},

number = {9},

pages = {093011},

abstract = {In recent years, the gap between theory and practice in quantum key distribution (QKD) has been significantly narrowed, particularly for QKD systems with arbitrarily flawed optical receivers. The status for QKD systems with imperfect light sources is however less satisfactory, in the sense that the resulting secure key rates are often overly dependent on the quality of state preparation. This is especially the case when the channel loss is high. Very recently, to overcome this limitation, Tamaki et al proposed a QKD protocol based on the so-called ‘rejected data analysis’, and showed that its security\textemdashin the limit of infinitely long keys\textemdashis almost independent of any encoding flaw in the qubit space, being this protocol compatible with the decoy state method. Here, as a step towards practical QKD, we show that a similar conclusion is reached in the finite-key regime, even when the intensity of the light source is unstable. More concretely, we derive security bounds for a wide class of realistic light sources and show that the bounds are also efficient in the presence of high channel loss. Our results strongly suggest the feasibility of long distance provably secure communication with imperfect light sources.},

keywords = {quantum cryptography},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevB.92.075312b,

title = {Quantum state tomography of large nuclear spins in a semiconductor quantum well: Optimal robustness against errors as quantified by condition numbers},

author = {Adam Miranowicz and \c{S} and Ji\v{r}\'{i} Bajer and Go Yusa and Nobuyuki Imoto and Yoshiro Hirayama and Franco Nori},

url = {https://link.aps.org/doi/10.1103/PhysRevB.92.075312},

doi = {10.1103/PhysRevB.92.075312},

year  = {2015},

date = {2015-08-01},

journal = {Phys. Rev. B},

volume = {92},

pages = {075312},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevB.92.075312,

title = {Quantum state tomography of large nuclear spins in a semiconductor quantum well: Optimal robustness against errors as quantified by condition numbers},

author = {Adam Miranowicz and \c{S} and Ji\v{r}\'{i} Bajer and Go Yusa and Nobuyuki Imoto and Yoshiro Hirayama and Franco Nori},

url = {https://link.aps.org/doi/10.1103/PhysRevB.92.075312},

doi = {10.1103/PhysRevB.92.075312},

year  = {2015},

date = {2015-08-01},

journal = {Phys. Rev. B},

volume = {92},

pages = {075312},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{6998043b,

title = {Fabrication and Characterization of Superconducting Nanowire Single-Photon Detectors on Si Waveguide},

author = {Kentaro Waki and Taro Yamashita and Shin-ichiro Inoue and Shigehito Miki and Hirotaka Terai and Rikizo Ikuta and Takashi Yamamoto and Nobuyuki Imoto},

doi = {10.1109/TASC.2014.2385836},

issn = {1051-8223},

year  = {2015},

date = {2015-06-01},

journal = {IEEE Transactions on Applied Superconductivity},

volume = {25},

number = {3},

pages = {1-4},

keywords = {superconducting detector},

pubstate = {published},

tppubtype = {article}

}

@article{6998043,

title = {Fabrication and Characterization of Superconducting Nanowire Single-Photon Detectors on Si Waveguide},

author = {Kentaro Waki and Taro Yamashita and Shin-ichiro Inoue and Shigehito Miki and Hirotaka Terai and Rikizo Ikuta and Takashi Yamamoto and Nobuyuki Imoto},

doi = {10.1109/TASC.2014.2385836},

issn = {1051-8223},

year  = {2015},

date = {2015-06-01},

journal = {IEEE Transactions on Applied Superconductivity},

volume = {25},

number = {3},

pages = {1-4},

keywords = {superconducting detector},

pubstate = {published},

tppubtype = {article}

}

@article{Tsujimoto:15b,

title = {Extracting an entangled photon pair from collectively decohered pairs at a telecommunication wavelength},

author = {Yoshiaki Tsujimoto and Yukihiro Sugiura and Makoto Ando and Daisuke Katsuse and Rikizo Ikuta and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-23-10-13545},

doi = {10.1364/OE.23.013545},

year  = {2015},

date = {2015-05-01},

journal = {Opt. Express},

volume = {23},

number = {10},

pages = {13545--13553},

publisher = {OSA},

abstract = {We experimentally demonstrated entanglement extraction scheme by using photons at the telecommunication band for optical-fiber-based quantum communications. We generated two pairs of non-degenerate polarization entangled photons at 780 nm and 1551 nm by spontaneous parametric down-conversion and distributed the two photons at 1551 nm through a collective phase damping channel which gives the same amount of random phase shift on the two photons. Through local operation and classical communication, we extracted an entangled photon pair from two phase-disturbed photon pairs. An observed fidelity of the extracted photon pair to a maximally entangled photon pair was 0.73 textpm 0.07 which clearly shows the recovery of entanglement.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Tsujimoto:15,

title = {Extracting an entangled photon pair from collectively decohered pairs at a telecommunication wavelength},

author = {Yoshiaki Tsujimoto and Yukihiro Sugiura and Makoto Ando and Daisuke Katsuse and Rikizo Ikuta and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-23-10-13545},

doi = {10.1364/OE.23.013545},

year  = {2015},

date = {2015-05-01},

journal = {Opt. Express},

volume = {23},

number = {10},

pages = {13545--13553},

publisher = {OSA},

abstract = {We experimentally demonstrated entanglement extraction scheme by using photons at the telecommunication band for optical-fiber-based quantum communications. We generated two pairs of non-degenerate polarization entangled photons at 780 nm and 1551 nm by spontaneous parametric down-conversion and distributed the two photons at 1551 nm through a collective phase damping channel which gives the same amount of random phase shift on the two photons. Through local operation and classical communication, we extracted an entangled photon pair from two phase-disturbed photon pairs. An observed fidelity of the extracted photon pair to a maximally entangled photon pair was 0.73 textpm 0.07 which clearly shows the recovery of entanglement.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevX.4.041039b,

title = {Measurement-Free Topological Protection Using Dissipative Feedback},

author = {Keisuke Fujii and Makoto Negoro and Nobuyuki Imoto and Masahiro Kitagawa},

url = {https://link.aps.org/doi/10.1103/PhysRevX.4.041039},

doi = {10.1103/PhysRevX.4.041039},

year  = {2014},

date = {2014-12-01},

journal = {Phys. Rev. X},

volume = {4},

pages = {041039},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.90.062123b,

title = {Optimal two-qubit tomography based on local and global measurements: Maximal robustness against errors as described by condition numbers},

author = {Adam Miranowicz and Karol Bartkiewicz and Jan Pe\v{r}ina and Masato Koashi and Nobuyuki Imoto and Franco Nori},

url = {https://link.aps.org/doi/10.1103/PhysRevA.90.062123},

doi = {10.1103/PhysRevA.90.062123},

year  = {2014},

date = {2014-12-01},

journal = {Phys. Rev. A},

volume = {90},

pages = {062123},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevX.4.041039,

title = {Measurement-Free Topological Protection Using Dissipative Feedback},

author = {Keisuke Fujii and Makoto Negoro and Nobuyuki Imoto and Masahiro Kitagawa},

url = {https://link.aps.org/doi/10.1103/PhysRevX.4.041039},

doi = {10.1103/PhysRevX.4.041039},

year  = {2014},

date = {2014-12-01},

journal = {Phys. Rev. X},

volume = {4},

pages = {041039},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.90.062123,

title = {Optimal two-qubit tomography based on local and global measurements: Maximal robustness against errors as described by condition numbers},

author = {Adam Miranowicz and Karol Bartkiewicz and Jan Pe\v{r}ina and Masato Koashi and Nobuyuki Imoto and Franco Nori},

url = {https://link.aps.org/doi/10.1103/PhysRevA.90.062123},

doi = {10.1103/PhysRevA.90.062123},

year  = {2014},

date = {2014-12-01},

journal = {Phys. Rev. A},

volume = {90},

pages = {062123},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.90.022304b,

title = {Quantum algorithm for an additive approximation of Ising partition functions},

author = {Akira Matsuo and Keisuke Fujii and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.90.022304},

doi = {10.1103/PhysRevA.90.022304},

year  = {2014},

date = {2014-08-01},

journal = {Phys. Rev. A},

volume = {90},

pages = {022304},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.90.022304,

title = {Quantum algorithm for an additive approximation of Ising partition functions},

author = {Akira Matsuo and Keisuke Fujii and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.90.022304},

doi = {10.1103/PhysRevA.90.022304},

year  = {2014},

date = {2014-08-01},

journal = {Phys. Rev. A},

volume = {90},

pages = {022304},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1367-2630-16-7-073003b,

title = {A weak-value model for virtual particles supplying the electric current in graphene: the minimal conductivity and the Schwinger mechanism},

author = {Kazuhiro Yokota and Nobuyuki Imoto},

url = {http://stacks.iop.org/1367-2630/16/i=7/a=073003},

year  = {2014},

date = {2014-07-01},

journal = {New Journal of Physics},

volume = {16},

number = {7},

pages = {073003},

abstract = {We propose a model for the electric current in graphene in which electric carriers are supplied by virtual particles allowed by the uncertainty relations. The process to make a virtual particle real is described by a weak value of a group velocity: the velocity is requisite for the electric field to give the virtual particle the appropriate changes of both energy and momentum. With the weak value, we approximately estimate the electric current, considering the ballistic transport of the electric carriers. The current shows the quasi-Ohmic with the minimal conductivity of the order of ##IMG## [http://ej.iop.org/images/1367-2630/16/7/073003/njp496797ieqn1.gif] $e^2/h$ per channel. Crossing a certain ballistic time scale, it is brought to obey the Schwinger mechanism.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1367-2630-16-7-073003,

title = {A weak-value model for virtual particles supplying the electric current in graphene: the minimal conductivity and the Schwinger mechanism},

author = {Kazuhiro Yokota and Nobuyuki Imoto},

url = {http://stacks.iop.org/1367-2630/16/i=7/a=073003},

year  = {2014},

date = {2014-07-01},

journal = {New Journal of Physics},

volume = {16},

number = {7},

pages = {073003},

abstract = {We propose a model for the electric current in graphene in which electric carriers are supplied by virtual particles allowed by the uncertainty relations. The process to make a virtual particle real is described by a weak value of a group velocity: the velocity is requisite for the electric field to give the virtual particle the appropriate changes of both energy and momentum. With the weak value, we approximately estimate the electric current, considering the ballistic transport of the electric carriers. The current shows the quasi-Ohmic with the minimal conductivity of the order of ##IMG## [http://ej.iop.org/images/1367-2630/16/7/073003/njp496797ieqn1.gif] $e^2/h$ per channel. Crossing a certain ballistic time scale, it is brought to obey the Schwinger mechanism.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{mizutani2014measurementb,

title = {Measurement-device-independent quantum key distribution for Scarani-Acin-Ribordy-Gisin 04 protocol},

author = {Akihiro Mizutani and Kiyoshi Tamaki and Rikizo Ikuta and Takashi Yamamoto and Nobuyuki Imoto},

doi = {10.1038/srep05236},

year  = {2014},

date = {2014-06-01},

journal = {Scientific reports},

volume = {4},

pages = {5236},

publisher = {Nature Publishing Group},

keywords = {quantum cryptography},

pubstate = {published},

tppubtype = {article}

}

@article{mizutani2014measurement,

title = {Measurement-device-independent quantum key distribution for Scarani-Acin-Ribordy-Gisin 04 protocol},

author = {Akihiro Mizutani and Kiyoshi Tamaki and Rikizo Ikuta and Takashi Yamamoto and Nobuyuki Imoto},

doi = {10.1038/srep05236},

year  = {2014},

date = {2014-06-01},

journal = {Scientific reports},

volume = {4},

pages = {5236},

publisher = {Nature Publishing Group},

keywords = {quantum cryptography},

pubstate = {published},

tppubtype = {article}

}

@article{Ikuta:14b,

title = {Frequency down-conversion of 637 nm light to the telecommunication band for non-classical light emitted from NV centers in diamond},

author = {Rikizo Ikuta and Toshiki Kobayashi and Shuto Yasui and Shigehito Miki and Taro Yamashita and Hirotaka Terai and Mikio Fujiwara and Takashi Yamamoto and Masato Koashi and Masahide Sasaki and Zhen Wang and Nobuyuki Imoto},

url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-22-9-11205},

doi = {10.1364/OE.22.011205},

year  = {2014},

date = {2014-05-01},

journal = {Opt. Express},

volume = {22},

number = {9},

pages = {11205--11214},

publisher = {OSA},

abstract = {We demonstrate a low-noise frequency down-conversion of photons at 637 nm to the telecommunication band at 1587 nm by the difference frequency generation in a periodically-poled lithium niobate. An internal conversion efficiency of the converter is estimated to be 0.44 at the maximum which is achieved by a pump power of 0.43 W, whereas a rate of internal background photons caused by the strong cw pump laser is estimated to be 9 kHz/mW within a bandwidth of about 1 nm. By using the experimental values related to the intrinsic property of the converter, and using the intensity correlation and the average photon number of a 637 nm input light pulse, we derive the intensity correlation of a converted telecom light pulse. Then we discuss feasibility of a single-photon frequency conversion to the telecommunication band for a long-distance quantum communication based on NV centers in diamond.},

keywords = {quantum frequency conversion},

pubstate = {published},

tppubtype = {article}

}

@article{Ikuta:14,

title = {Frequency down-conversion of 637 nm light to the telecommunication band for non-classical light emitted from NV centers in diamond},

author = {Rikizo Ikuta and Toshiki Kobayashi and Shuto Yasui and Shigehito Miki and Taro Yamashita and Hirotaka Terai and Mikio Fujiwara and Takashi Yamamoto and Masato Koashi and Masahide Sasaki and Zhen Wang and Nobuyuki Imoto},

url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-22-9-11205},

doi = {10.1364/OE.22.011205},

year  = {2014},

date = {2014-05-01},

journal = {Opt. Express},

volume = {22},

number = {9},

pages = {11205--11214},

publisher = {OSA},

abstract = {We demonstrate a low-noise frequency down-conversion of photons at 637 nm to the telecommunication band at 1587 nm by the difference frequency generation in a periodically-poled lithium niobate. An internal conversion efficiency of the converter is estimated to be 0.44 at the maximum which is achieved by a pump power of 0.43 W, whereas a rate of internal background photons caused by the strong cw pump laser is estimated to be 9 kHz/mW within a bandwidth of about 1 nm. By using the experimental values related to the intrinsic property of the converter, and using the intensity correlation and the average photon number of a 637 nm input light pulse, we derive the intensity correlation of a converted telecom light pulse. Then we discuss feasibility of a single-photon frequency conversion to the telecommunication band for a long-distance quantum communication based on NV centers in diamond.},

keywords = {quantum frequency conversion},

pubstate = {published},

tppubtype = {article}

}

@article{1367-2630-16-2-023005b,

title = {Universal gates for transforming multipartite entangled Dicke states},

author = {Toshiki Kobayashi and Rikizo Ikuta and \c{S} and Mark Tame and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

url = {http://stacks.iop.org/1367-2630/16/i=2/a=023005},

year  = {2014},

date = {2014-02-01},

journal = {New Journal of Physics},

volume = {16},

number = {2},

pages = {023005},

abstract = {We determine the minimal number of qubits that it is necessary to have access to in order to transform Dicke states into other Dicke states. In general, the number of qubits in Dicke states cannot be increased via transformation gates by accessing only a single qubit, in direct contrast to other multipartite entangled states such as GHZ, W and cluster states. We construct a universal optimal gate which adds spin-up qubits or spin-down qubits to any Dicke state by minimal access. We also show the existence of a universal gate which transforms any size of Dicke state as long as it has access to at least the required number of qubits. Our results have important consequences for the generation of Dicke states in physical systems such as ion traps, all-optical setups and cavity-quantum electrodynamic settings where they can be used for a variety of quantum information processing tasks.},

keywords = {entanglement},

pubstate = {published},

tppubtype = {article}

}

@article{1367-2630-16-2-023005,

title = {Universal gates for transforming multipartite entangled Dicke states},

author = {Toshiki Kobayashi and Rikizo Ikuta and \c{S} and Mark Tame and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

url = {http://stacks.iop.org/1367-2630/16/i=2/a=023005},

year  = {2014},

date = {2014-02-01},

journal = {New Journal of Physics},

volume = {16},

number = {2},

pages = {023005},

abstract = {We determine the minimal number of qubits that it is necessary to have access to in order to transform Dicke states into other Dicke states. In general, the number of qubits in Dicke states cannot be increased via transformation gates by accessing only a single qubit, in direct contrast to other multipartite entangled states such as GHZ, W and cluster states. We construct a universal optimal gate which adds spin-up qubits or spin-down qubits to any Dicke state by minimal access. We also show the existence of a universal gate which transforms any size of Dicke state as long as it has access to at least the required number of qubits. Our results have important consequences for the generation of Dicke states in physical systems such as ion traps, all-optical setups and cavity-quantum electrodynamic settings where they can be used for a variety of quantum information processing tasks.},

keywords = {entanglement},

pubstate = {published},

tppubtype = {article}

}

@article{Ikuta:13b,

title = {Observation of two output light pulses from a partial wavelength converter preserving phase of an input light at a single-photon level},

author = {Rikizo Ikuta and Toshiki Kobayashi and Hiroshi Kato and Shigehito Miki and Taro Yamashita and Hirotaka Terai and Mikio Fujiwara and Takashi Yamamoto and Masahide Sasaki and Zhen Wang and Masato Koashi and Nobuyuki Imoto},

url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-21-23-27865},

doi = {10.1364/OE.21.027865},

year  = {2013},

date = {2013-11-01},

journal = {Opt. Express},

volume = {21},

number = {23},

pages = {27865--27872},

publisher = {OSA},

abstract = {We experimentally demonstrate that both of the two output light pulses of different wavelengths from a wavelength converter with various branching ratios preserve phase information of an input light at a single-photon level. In our experiment, we converted temporally-separated two coherent light pulses with average photon numbers of $sim$ 0.1 at 780 nm to light pulses at 1522 nm by using difference-frequency generation in a periodically-poled lithium niobate waveguide. We observed an interference between temporally-separated two modes for both the converted and the unconverted light pulses at various values of the conversion efficiency. We observed interference visibilities greater than 0.88 without suppressing the background noises for any value of the conversion efficiency the wavelength converter achieves. At a conversion efficiency of $sim$ 0.5, the observed visibilities are 0.98 for the unconverted light and 0.99 for the converted light. Such a phase-preserving wavelength converter with high visibilities will be useful for manipulating quantum states encoded in the frequency degrees of freedom.},

keywords = {quantum frequency conversion},

pubstate = {published},

tppubtype = {article}

}

@article{Ikuta:13,

title = {Observation of two output light pulses from a partial wavelength converter preserving phase of an input light at a single-photon level},

author = {Rikizo Ikuta and Toshiki Kobayashi and Hiroshi Kato and Shigehito Miki and Taro Yamashita and Hirotaka Terai and Mikio Fujiwara and Takashi Yamamoto and Masahide Sasaki and Zhen Wang and Masato Koashi and Nobuyuki Imoto},

url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-21-23-27865},

doi = {10.1364/OE.21.027865},

year  = {2013},

date = {2013-11-01},

journal = {Opt. Express},

volume = {21},

number = {23},

pages = {27865--27872},

publisher = {OSA},

abstract = {We experimentally demonstrate that both of the two output light pulses of different wavelengths from a wavelength converter with various branching ratios preserve phase information of an input light at a single-photon level. In our experiment, we converted temporally-separated two coherent light pulses with average photon numbers of $sim$ 0.1 at 780 nm to light pulses at 1522 nm by using difference-frequency generation in a periodically-poled lithium niobate waveguide. We observed an interference between temporally-separated two modes for both the converted and the unconverted light pulses at various values of the conversion efficiency. We observed interference visibilities greater than 0.88 without suppressing the background noises for any value of the conversion efficiency the wavelength converter achieves. At a conversion efficiency of $sim$ 0.5, the observed visibilities are 0.98 for the unconverted light and 0.99 for the converted light. Such a phase-preserving wavelength converter with high visibilities will be useful for manipulating quantum states encoded in the frequency degrees of freedom.},

keywords = {quantum frequency conversion},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.88.042317b,

title = {Nonclassical two-photon interference between independent telecommunication light pulses converted by difference-frequency generation},

author = {Rikizo Ikuta and Toshiki Kobayashi and Hiroshi Kato and Shigehito Miki and Taro Yamashita and Hirotaka Terai and Mikio Fujiwara and Takashi Yamamoto and Masato Koashi and Masahide Sasaki and Zhen Wang and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.88.042317},

doi = {10.1103/PhysRevA.88.042317},

year  = {2013},

date = {2013-10-01},

journal = {Phys. Rev. A},

volume = {88},

pages = {042317},

publisher = {American Physical Society},

keywords = {quantum frequency conversion},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.88.042317,

title = {Nonclassical two-photon interference between independent telecommunication light pulses converted by difference-frequency generation},

author = {Rikizo Ikuta and Toshiki Kobayashi and Hiroshi Kato and Shigehito Miki and Taro Yamashita and Hirotaka Terai and Mikio Fujiwara and Takashi Yamamoto and Masato Koashi and Masahide Sasaki and Zhen Wang and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.88.042317},

doi = {10.1103/PhysRevA.88.042317},

year  = {2013},

date = {2013-10-01},

journal = {Phys. Rev. A},

volume = {88},

pages = {042317},

publisher = {American Physical Society},

keywords = {quantum frequency conversion},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevLett.111.020502b,

title = {Secure Entanglement Distillation for Double-Server Blind Quantum Computation},

author = {Tomoyuki Morimae and Keisuke Fujii},

url = {https://link.aps.org/doi/10.1103/PhysRevLett.111.020502},

doi = {10.1103/PhysRevLett.111.020502},

year  = {2013},

date = {2013-07-01},

journal = {Phys. Rev. Lett.},

volume = {111},

pages = {020502},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevLett.111.020502,

title = {Secure Entanglement Distillation for Double-Server Blind Quantum Computation},

author = {Tomoyuki Morimae and Keisuke Fujii},

url = {https://link.aps.org/doi/10.1103/PhysRevLett.111.020502},

doi = {10.1103/PhysRevLett.111.020502},

year  = {2013},

date = {2013-07-01},

journal = {Phys. Rev. Lett.},

volume = {111},

pages = {020502},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.87.052325b,

title = {Robustness of quantum communication based on a decoherence-free subspace using a counter-propagating weak coherent light pulse},

author = {Hidetoshi Kumagai and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.87.052325},

doi = {10.1103/PhysRevA.87.052325},

year  = {2013},

date = {2013-05-01},

journal = {Phys. Rev. A},

volume = {87},

pages = {052325},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.87.050301b,

title = {Blind quantum computation protocol in which Alice only makes measurements},

author = {Tomoyuki Morimae and Keisuke Fujii},

url = {https://link.aps.org/doi/10.1103/PhysRevA.87.050301},

doi = {10.1103/PhysRevA.87.050301},

year  = {2013},

date = {2013-05-01},

journal = {Phys. Rev. A},

volume = {87},

pages = {050301},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.87.052325,

title = {Robustness of quantum communication based on a decoherence-free subspace using a counter-propagating weak coherent light pulse},

author = {Hidetoshi Kumagai and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.87.052325},

doi = {10.1103/PhysRevA.87.052325},

year  = {2013},

date = {2013-05-01},

journal = {Phys. Rev. A},

volume = {87},

pages = {052325},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.87.050301,

title = {Blind quantum computation protocol in which Alice only makes measurements},

author = {Tomoyuki Morimae and Keisuke Fujii},

url = {https://link.aps.org/doi/10.1103/PhysRevA.87.050301},

doi = {10.1103/PhysRevA.87.050301},

year  = {2013},

date = {2013-05-01},

journal = {Phys. Rev. A},

volume = {87},

pages = {050301},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevLett.110.120502b,

title = {Measurement-Based Quantum Computation on Symmetry Breaking Thermal States},

author = {Keisuke Fujii and Yoshifumi Nakata and Masayuki Ohzeki and Mio Murao},

url = {https://link.aps.org/doi/10.1103/PhysRevLett.110.120502},

doi = {10.1103/PhysRevLett.110.120502},

year  = {2013},

date = {2013-03-01},

journal = {Phys. Rev. Lett.},

volume = {110},

pages = {120502},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevLett.110.120502,

title = {Measurement-Based Quantum Computation on Symmetry Breaking Thermal States},

author = {Keisuke Fujii and Yoshifumi Nakata and Masayuki Ohzeki and Mio Murao},

url = {https://link.aps.org/doi/10.1103/PhysRevLett.110.120502},

doi = {10.1103/PhysRevLett.110.120502},

year  = {2013},

date = {2013-03-01},

journal = {Phys. Rev. Lett.},

volume = {110},

pages = {120502},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.87.022321b,

title = {Fundamental limit to qubit control with coherent field},

author = {Kazuhiro Igeta and Nobuyuki Imoto and Masato Koashi},

url = {https://link.aps.org/doi/10.1103/PhysRevA.87.022321},

doi = {10.1103/PhysRevA.87.022321},

year  = {2013},

date = {2013-02-01},

journal = {Phys. Rev. A},

volume = {87},

pages = {022321},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.87.022321,

title = {Fundamental limit to qubit control with coherent field},

author = {Kazuhiro Igeta and Nobuyuki Imoto and Masato Koashi},

url = {https://link.aps.org/doi/10.1103/PhysRevA.87.022321},

doi = {10.1103/PhysRevA.87.022321},

year  = {2013},

date = {2013-02-01},

journal = {Phys. Rev. A},

volume = {87},

pages = {022321},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.87.010301b,

title = {High-fidelity conversion of photonic quantum information to telecommunication wavelength with superconducting single-photon detectors},

author = {Rikizo Ikuta and Hiroshi Kato and Yoshiaki Kusaka and Shigehito Miki and Taro Yamashita and Hirotaka Terai and Mikio Fujiwara and Takashi Yamamoto and Masato Koashi and Masahide Sasaki and Zhen Wang and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.87.010301},

doi = {10.1103/PhysRevA.87.010301},

year  = {2013},

date = {2013-01-01},

journal = {Phys. Rev. A},

volume = {87},

pages = {010301},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.87.010301,

title = {High-fidelity conversion of photonic quantum information to telecommunication wavelength with superconducting single-photon detectors},

author = {Rikizo Ikuta and Hiroshi Kato and Yoshiaki Kusaka and Shigehito Miki and Taro Yamashita and Hirotaka Terai and Mikio Fujiwara and Takashi Yamamoto and Masato Koashi and Masahide Sasaki and Zhen Wang and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.87.010301},

doi = {10.1103/PhysRevA.87.010301},

year  = {2013},

date = {2013-01-01},

journal = {Phys. Rev. A},

volume = {87},

pages = {010301},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevE.86.051121b,

title = {Duality analysis on random planar lattices},

author = {Masayuki Ohzeki and Keisuke Fujii},

url = {https://link.aps.org/doi/10.1103/PhysRevE.86.051121},

doi = {10.1103/PhysRevE.86.051121},

year  = {2012},

date = {2012-11-01},

journal = {Phys. Rev. E},

volume = {86},

pages = {051121},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevE.86.051121,

title = {Duality analysis on random planar lattices},

author = {Masayuki Ohzeki and Keisuke Fujii},

url = {https://link.aps.org/doi/10.1103/PhysRevE.86.051121},

doi = {10.1103/PhysRevE.86.051121},

year  = {2012},

date = {2012-11-01},

journal = {Phys. Rev. E},

volume = {86},

pages = {051121},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{morimae2012blindb,

title = {Blind topological measurement-based quantum computation},

author = {Tomoyuki Morimae and Keisuke Fujii},

doi = {10.1038/ncomms2043},

year  = {2012},

date = {2012-09-01},

journal = {Nature communications},

volume = {3},

pages = {1036},

publisher = {Nature Publishing Group},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{morimae2012blind,

title = {Blind topological measurement-based quantum computation},

author = {Tomoyuki Morimae and Keisuke Fujii},

doi = {10.1038/ncomms2043},

year  = {2012},

date = {2012-09-01},

journal = {Nature communications},

volume = {3},

pages = {1036},

publisher = {Nature Publishing Group},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1367-2630-14-8-083021b,

title = {A strange weak value in spontaneous pair productions via a supercritical step potential},

author = {Kazuhiro Yokota and Nobuyuki Imoto},

url = {http://stacks.iop.org/1367-2630/14/i=8/a=083021},

year  = {2012},

date = {2012-08-01},

journal = {New Journal of Physics},

volume = {14},

number = {8},

pages = {083021},

abstract = {We consider a case when a weak value is introduced as a physical quantity rather than as an average of weak measurements. The case we treat is a time evolution of a particle by the 1 + 1-dimensional Dirac equation. In particular, in a spontaneous pair production via a supercritical step potential, a quantitative explanation can be given by a weak value for the group velocity of the particle. We also show that the condition for the pair production (supercriticality) corresponds to the condition when the weak value takes a strange value (superluminal velocity).},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.86.020303b,

title = {Error and loss tolerances of surface codes with general lattice structures},

author = {Keisuke Fujii and Yuuki Tokunaga},

url = {https://link.aps.org/doi/10.1103/PhysRevA.86.020303},

doi = {10.1103/PhysRevA.86.020303},

year  = {2012},

date = {2012-08-01},

journal = {Phys. Rev. A},

volume = {86},

pages = {020303},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1367-2630-14-8-083021,

title = {A strange weak value in spontaneous pair productions via a supercritical step potential},

author = {Kazuhiro Yokota and Nobuyuki Imoto},

url = {http://stacks.iop.org/1367-2630/14/i=8/a=083021},

year  = {2012},

date = {2012-08-01},

journal = {New Journal of Physics},

volume = {14},

number = {8},

pages = {083021},

abstract = {We consider a case when a weak value is introduced as a physical quantity rather than as an average of weak measurements. The case we treat is a time evolution of a particle by the 1 + 1-dimensional Dirac equation. In particular, in a spontaneous pair production via a supercritical step potential, a quantitative explanation can be given by a weak value for the group velocity of the particle. We also show that the condition for the pair production (supercriticality) corresponds to the condition when the weak value takes a strange value (superluminal velocity).},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.86.020303,

title = {Error and loss tolerances of surface codes with general lattice structures},

author = {Keisuke Fujii and Yuuki Tokunaga},

url = {https://link.aps.org/doi/10.1103/PhysRevA.86.020303},

doi = {10.1103/PhysRevA.86.020303},

year  = {2012},

date = {2012-08-01},

journal = {Phys. Rev. A},

volume = {86},

pages = {020303},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{morimae2012notb,

title = {Not all physical errors can be linear CPTP maps in a correlation space},

author = {Tomoyuki Morimae and Keisuke Fujii},

doi = {10.1038/srep00508},

year  = {2012},

date = {2012-07-01},

journal = {Scientific Reports},

volume = {2},

pages = {508},

publisher = {Nature Publishing Group},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{morimae2012not,

title = {Not all physical errors can be linear CPTP maps in a correlation space},

author = {Tomoyuki Morimae and Keisuke Fujii},

doi = {10.1038/srep00508},

year  = {2012},

date = {2012-07-01},

journal = {Scientific Reports},

volume = {2},

pages = {508},

publisher = {Nature Publishing Group},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.85.062309b,

title = {Quantum repeaters and computation by a single module: Remote nondestructive parity measurement},

author = {Koji Azuma and Hitoshi Takeda and Masato Koashi and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.85.062309},

doi = {10.1103/PhysRevA.85.062309},

year  = {2012},

date = {2012-06-01},

journal = {Phys. Rev. A},

volume = {85},

pages = {062309},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.85.062309,

title = {Quantum repeaters and computation by a single module: Remote nondestructive parity measurement},

author = {Koji Azuma and Hitoshi Takeda and Masato Koashi and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.85.062309},

doi = {10.1103/PhysRevA.85.062309},

year  = {2012},

date = {2012-06-01},

journal = {Phys. Rev. A},

volume = {85},

pages = {062309},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.85.032338b,

title = {Computational power and correlation in a quantum computational tensor network},

author = {Keisuke Fujii and Tomoyuki Morimae},

url = {https://link.aps.org/doi/10.1103/PhysRevA.85.032338},

doi = {10.1103/PhysRevA.85.032338},

year  = {2012},

date = {2012-03-01},

journal = {Phys. Rev. A},

volume = {85},

pages = {032338},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.85.032338,

title = {Computational power and correlation in a quantum computational tensor network},

author = {Keisuke Fujii and Tomoyuki Morimae},

url = {https://link.aps.org/doi/10.1103/PhysRevA.85.032338},

doi = {10.1103/PhysRevA.85.032338},

year  = {2012},

date = {2012-03-01},

journal = {Phys. Rev. A},

volume = {85},

pages = {032338},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.85.010304b,

title = {Topologically protected measurement-based quantum computation on the thermal state of a nearest-neighbor two-body Hamiltonian with spin-3/2 particles},

author = {Keisuke Fujii and Tomoyuki Morimae},

url = {https://link.aps.org/doi/10.1103/PhysRevA.85.010304},

doi = {10.1103/PhysRevA.85.010304},

year  = {2012},

date = {2012-01-01},

journal = {Phys. Rev. A},

volume = {85},

pages = {010304},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.85.010304,

title = {Topologically protected measurement-based quantum computation on the thermal state of a nearest-neighbor two-body Hamiltonian with spin-3/2 particles},

author = {Keisuke Fujii and Tomoyuki Morimae},

url = {https://link.aps.org/doi/10.1103/PhysRevA.85.010304},

doi = {10.1103/PhysRevA.85.010304},

year  = {2012},

date = {2012-01-01},

journal = {Phys. Rev. A},

volume = {85},

pages = {010304},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ikuta2011wideb,

title = {Wide-band quantum interface for visible-to-telecommunication wavelength conversion},

author = {Rikizo Ikuta and Yoshiaki Kusaka and Tsuyoshi Kitano and Hiroshi Kato and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

url = {http://dx.doi.org/10.1038/ncomms1544},

doi = {10.1038/ncomms1544},

year  = {2011},

date = {2011-11-01},

journal = {Nature Communications},

volume = {2},

pages = {537},

publisher = {Nature Publishing Group},

note = {press release by Osaka univ.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ikuta2011wide,

title = {Wide-band quantum interface for visible-to-telecommunication wavelength conversion},

author = {Rikizo Ikuta and Yoshiaki Kusaka and Tsuyoshi Kitano and Hiroshi Kato and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

url = {http://dx.doi.org/10.1038/ncomms1544},

doi = {10.1038/ncomms1544},

year  = {2011},

date = {2011-11-01},

journal = {Nature Communications},

volume = {2},

pages = {1544},

publisher = {Nature Publishing Group},

note = {press release by Osaka univ.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1367-2630-13-10-103003b,

title = {An optical fusion gate for W-states},

author = {\c{S} and Eiji Matsunaga and Toshiyuki Tashima and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

url = {http://stacks.iop.org/1367-2630/13/i=10/a=103003},

year  = {2011},

date = {2011-10-01},

journal = {New Journal of Physics},

volume = {13},

number = {10},

pages = {103003},

abstract = {We introduce a simple optical gate to fuse arbitrary-size polarization entangled W-states to prepare larger W-states. The gate requires a polarizing beam splitter (PBS), a half-wave plate (HWP) and two photon detectors. We study, numerically and analytically, the necessary resource consumption for preparing larger W-states by fusing smaller ones with the proposed fusion gate. We show analytically that resource requirement scales at most sub-exponentially with the increasing size of the state to be prepared. We numerically determine the resource cost for fusion without recycling where W-states of arbitrary size can be optimally prepared. Moreover, we introduce another strategy that is based on recycling and outperforms the optimal strategy for the non-recycling case.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{1367-2630-13-10-103003,

title = {An optical fusion gate for W-states},

author = {\c{S} and Eiji Matsunaga and Toshiyuki Tashima and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

url = {http://stacks.iop.org/1367-2630/13/i=10/a=103003},

year  = {2011},

date = {2011-10-01},

journal = {New Journal of Physics},

volume = {13},

number = {10},

pages = {103003},

abstract = {We introduce a simple optical gate to fuse arbitrary-size polarization entangled W-states to prepare larger W-states. The gate requires a polarizing beam splitter (PBS), a half-wave plate (HWP) and two photon detectors. We study, numerically and analytically, the necessary resource consumption for preparing larger W-states by fusing smaller ones with the proposed fusion gate. We show analytically that resource requirement scales at most sub-exponentially with the increasing size of the state to be prepared. We numerically determine the resource cost for fusion without recycling where W-states of arbitrary size can be optimally prepared. Moreover, we introduce another strategy that is based on recycling and outperforms the optimal strategy for the non-recycling case.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.84.022308b,

title = {Cheat-sensitive commitment of a classical bit coded in a block of $m$ times $n$ round-trip qubits},

author = {Kaoru Shimizu and Hiroyuki Fukasaka and Kiyoshi Tamaki and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.84.022308},

doi = {10.1103/PhysRevA.84.022308},

year  = {2011},

date = {2011-08-01},

journal = {Phys. Rev. A},

volume = {84},

pages = {022308},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.84.022308,

title = {Cheat-sensitive commitment of a classical bit coded in a block of $m$ times $n$ round-trip qubits},

author = {Kaoru Shimizu and Hiroyuki Fukasaka and Kiyoshi Tamaki and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.84.022308},

doi = {10.1103/PhysRevA.84.022308},

year  = {2011},

date = {2011-08-01},

journal = {Phys. Rev. A},

volume = {84},

pages = {022308},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevLett.106.110503b,

title = {Efficient Decoherence-Free Entanglement Distribution over Lossy Quantum Channels},

author = {Rikizo Ikuta and Yohei Ono and Toshiyuki Tashima and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevLett.106.110503},

doi = {10.1103/PhysRevLett.106.110503},

year  = {2011},

date = {2011-03-01},

journal = {Phys. Rev. Lett.},

volume = {106},

pages = {110503},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevLett.106.110503,

title = {Efficient Decoherence-Free Entanglement Distribution over Lossy Quantum Channels},

author = {Rikizo Ikuta and Yohei Ono and Toshiyuki Tashima and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevLett.106.110503},

doi = {10.1103/PhysRevLett.106.110503},

year  = {2011},

date = {2011-03-01},

journal = {Phys. Rev. Lett.},

volume = {106},

pages = {110503},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.83.012314b,

title = {Optimal local expansion of $W$ states using linear optics and Fock states},

author = {Rikizo Ikuta and Toshiyuki Tashima and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.83.012314},

doi = {10.1103/PhysRevA.83.012314},

year  = {2011},

date = {2011-01-01},

journal = {Phys. Rev. A},

volume = {83},

pages = {012314},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.83.012314,

title = {Optimal local expansion of $W$ states using linear optics and Fock states},

author = {Rikizo Ikuta and Toshiyuki Tashima and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.83.012314},

doi = {10.1103/PhysRevA.83.012314},

year  = {2011},

date = {2011-01-01},

journal = {Phys. Rev. A},

volume = {83},

pages = {012314},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevLett.105.210503b,

title = {Demonstration of Local Expansion Toward Large-Scale Entangled Webs},

author = {Toshiyuki Tashima and Tsuyoshi Kitano and \c{S} and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevLett.105.210503},

doi = {10.1103/PhysRevLett.105.210503},

year  = {2010},

date = {2010-11-01},

journal = {Phys. Rev. Lett.},

volume = {105},

pages = {210503},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevLett.105.210503,

title = {Demonstration of Local Expansion Toward Large-Scale Entangled Webs},

author = {Toshiyuki Tashima and Tsuyoshi Kitano and \c{S} and Takashi Yamamoto and Masato Koashi and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevLett.105.210503},

doi = {10.1103/PhysRevLett.105.210503},

year  = {2010},

date = {2010-11-01},

journal = {Phys. Rev. Lett.},

volume = {105},

pages = {210503},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.81.022325b,

title = {Tight bound on coherent-state-based entanglement generation over lossy channels},

author = {Koji Azuma and Naoya Sota and Masato Koashi and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.81.022325},

doi = {10.1103/PhysRevA.81.022325},

year  = {2010},

date = {2010-02-01},

journal = {Phys. Rev. A},

volume = {81},

pages = {022325},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevA.81.022325,

title = {Tight bound on coherent-state-based entanglement generation over lossy channels},

author = {Koji Azuma and Naoya Sota and Masato Koashi and Nobuyuki Imoto},

url = {https://link.aps.org/doi/10.1103/PhysRevA.81.022325},

doi = {10.1103/PhysRevA.81.022325},

year  = {2010},

date = {2010-02-01},

journal = {Phys. Rev. A},

volume = {81},

pages = {022325},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{SEKI20101534b,

title = {Comparison of timing jitter between NbN superconducting single-photon detector and avalanche photodiode},

author = {Tadakiyo Seki and Hiroyuki Shibata and Hiroki Takesue and Yasuhiro Tokura and Nobuyuki Imoto},

url = {http://www.sciencedirect.com/science/article/pii/S0921453410004120},

doi = {https://doi.org/10.1016/j.physc.2010.05.156},

issn = {0921-4534},

year  = {2010},

date = {2010-01-01},

journal = {Physica C: Superconductivity and its Applications},

volume = {470},

number = {20},

pages = {1534 - 1537},

note = {Proceedings of the 22nd International Symposium on Superconductivity (ISS 2009)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}