Publications

@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{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{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{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{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{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{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{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{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{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{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{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: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{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{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{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}

}