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@Seminars
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2011
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Global COE Seminar

Data and Time:April 12th. 2011,14:40-16:10

Location:Graduate school of Engineering Science B103, Toyonaka campus

Lecturer:Aephraim Steinberg (Centre for Quantum Information & Quantum Control and Institute for Optical Sciences, Department of Physics, University of Toronto)

Title:New Experimental Techniques in Quantum Measurement

Abstract:
While quantum measurement remains the central philosophical conundrum of quantum mechanics, it has recently grown into a respectable (read: experimental!) discipline as well. New perspectives on measurement have grown out of the new technological possibilities, but also out of attempts to design systems for quantum information processing, which promise to be exponentially more powerful than any possible classical computer. I will present several examples of how our current ideas on quantum measurement go far beyond the usual textbook treatments, using examples from our entangled-photon and ultracold-atoms laboratories in Toronto. Topics will include weak measurement, "interaction-free" measurement, Hardy's Paradox, measurement-induced quantum logic, and techniques for controlling and characterizing the coherence of quantum systems.

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Global COE Seminar[11]

Data and Time:January 28th. 2011,16F30-

Location:Building J in Faculty of Engineering Science, Toyonaka campus

Lecturer:Seth Lloyd (MIT, USA)

Title:Sending a photon backwards in time

Abstract:
Ever since Einstein, physicists have argued about whether time travel is consistent with the laws of physics, and, if so, how it might be accomplished. This talk presents a new theory of time travel based on quantum teleportation. Unlike previous theories, the theory can be tested experimentally. I report on an experimental realization of the `grandfather paradox': we send a photon a few billionths of a second backwards in time and have it try to `kill' its previous self.

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Global COE Seminar[10]

Data and Time:January 28th. 2011,15F30-

Location:Building J in Faculty of Engineering Science, Toyonaka campus

Lecturer:Seth Lloyd (MIT, USA)

Title:Quantum transport in biological systems

Abstract:
Recent experimental observations have shown that quantum coherence plays an important role in photosynthetic energy transport. Photosynthetic molecules are large and complex, containing both regular structures, such as rings of chromophores, and apparently irregular structures. This talk proposes a general theory of the role of symmetry and asymmetry in quantum transport in biomolecules. I will show that collective coherent effects, including entanglement, can give rise to substantial enhancements of excitonic lifetimes and energy transport.

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2008
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Global COE Seminar

Data and Time:December 8, 2008 15:00-

Location:Graduate school of Engineering Science A304

Lecture:Philip WaltheriAssistant Professor, Quantum Optics, Quantum Nanophysics,
Quantum Information Faculty of Physics, University of Vienna, Austriaj

Title:Experimental one-way quantum computing

Abstract:
Photons have an intrinsic lack of decoherence and are simple to control by
standard off-the-shelf components. Therefore optical qubits are playing an
important role in investigating foundations of quantum information
processing. Furthermore, photonic qubits for quantum computation are
particularly attractive because they could interface to various quantum
communication applications. In recent years, one-way quantum computing has
become an exciting alternative to existing proposals for quantum computers.
In this specific model, coherent quantum information processing is
accomplished via a sequence of single-qubit measurements applied to an
entangled resource known as cluster state. Here we show the experimental
realization of various quantum algorithms on a photonic four-qubit cluster
state, which is generated by means of parametric down-conversion. We were
able to implement simple quantum algorithms, consisting of a few gates.
Among them the so-called Deutsch-Josza algorithm, an important quantum
algorithm that is capable of distinguishing whether a function is constant
or balanced and the implementation of a quantum game known as Prisoner's
Dilemma. Playing such a game is essentially the execution of a quantum
algorithm in which the players can resolve the "dilemma" that occurs in the
classical version of this game. Finally we were able to design
decoherence-free subspaces for cluster states which achieve remarkable
protection from environmentally induced decoherence, delivering nearly ideal
computational outcomes.

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Global COE Seminar

Data and Time:August 28, 2008 14:00-

Location:Graduate School of Engineering Science D412 seminar room

Lecture:Dr. Adam Miranowicz
(Adam Mickiewicz University, Poland)

Title:Detection of quantum entanglement via matrices of moments

Abstract:
Entanglement criteria for continuous and discrete bipartite quantum states
based on moments of annihilation and creation operators are described by
generalizing the idea of Shchukin-Vogel criterion. If a state is separable,
then the corresponding matrix of moments is separable too. Generalized criteria,
based on the separability properties of the matrix of moments, are thus derived.
In particular, a new criterion based on realignment of moments in the matrix is
proposed as an analogue of the standard realignment criterion for density matrices.
Other inseparability inequalities are obtained by applying positive maps to the matrix
of moments. Usefulness of the generalized Shchukin-Vogel criteria to describe
bipartite-entanglement of more than two modes is demonstrated.

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2007
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Osaka University the 21st Century COE Program

Data and Time:October 2, 2007 10:00-12:00

Location:Graduate School of Engineering Science D404-408 seminar room

Lecture:Yu-xi Liu
(Frontier Research System, The Institute of Physical and
Chemical Research, Wako-shi, Saitama 351-0198, Japan)

Title:Quantum Information Processor based on Superconducting Quantum Devices

Abstract:
Quantum devices using Josephson junctions can be used
as artificial atoms for demonstrating quantum phenomena
at macroscopic scales. These artificial atoms are good
candidates for single-photon production and artificial-atom
lasing. However, when using their two lowest levels, these
devices are called qubits. Basically, there are four different
kinds of superconducting qubits. We have studied several aspects of
the superconducting qubits, e.g., circuit QED, micromaser,
adiabatic control for quantum states, switchable coupling, and scalable
circuits.
Here, I will briefly review recent experiments on the superconducting qubits.
In particular, I will pedagogically explain how to theoretically
describe single superconducting qubits and how to use them to build
superconducting quantum circuits.

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2006
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SORST lecture presentation

Data and Time:December 7, 2006 10:30-12:00

Location:Graduate School of Engineering Science D222

Lecture:Onur Hosten (University of Illinois at Urbana-Champaign, Kwiat group)

Title:Counterfactual Computation and the Meaning of Counterfactuality in Quantum Processes

Abstract:
The logic behind the coherent nature of quantum information processing often deviates from intuitive reasoning, leading to surprising effects. 'Counterfactual computation' (CFC) constitutes a striking example, showing that one can infer the potential outcome from a quantum computer, even if the computer is not run. Relying on similar arguments to 'interaction-free' measurements CFC is accomplished by putting the computer in a superposition of 'running' (|On>) and 'not running' (|Off>) and then interfering the two histories. Conditional on the yet-unknown outcome of the computation, sometimes one can counterfactually infer information about the solution. I will present the first demonstration of CFC, implementing Grover's search algorithm as an example, following an all-optical approach. It was believed that the overall probability of such counterfactual inference is intrinsically limited so that it could not perform better on average than random guesses. However, using a "chained" version of the quantum Zeno effect, I will show how to beat the random guessing limit, and also show that in certain circumstances CFC can eliminate decoherence-induced errors. I will conclude with some of the ongoing debates on the definition of counterfactuality.


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CREST lecture presentation

Date and Time:December 5, 2006 16:20-17:50

Location:Graduate School of Engineering Science G508

Lecture:Michal Horodecki (Institute of Theoretical Physics and Astrophysics,
University of Gdansk, Poland)

Title:Negative Information


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Osaka University the 21st Century COE Program

Date and Time:December 4, 2006 16:20-17:50

Location:Graduate School of Engineering Science D404-408

Lecture:
[1] Michal Horodecki,
@@Institute of Theoretical Physics and Astrophysics, University of Gdansk, Poland
[2] Adam Miranowicz,
@@Adam Mickiewicz University, Poznan, Poland

Title:
[1]"Unconditionally secure quantum key distribution over channels with zero quantum
@@capacity"
[2]"Quantum state tomography of optical fields and nuclear spins in nano-structures"


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Osaka University the 21st Century COE Program

Date and Time:November 24,2006 14:40-16:10

Location:Graduate School of Engineering Science D412 seminar room

Lecture:
[1] Wenjamin Rosenfeld,
@@PhD Student, Department for Physics, Ludwig-Maximillians-University Munich,
@@D-80797 Munich, Germany
[2] Witlef Wieczorek,
@@PhD Student, 1. Max-Planck-Institute for Quantum Optics, 2. Department for Physics,
@@Ludwig-Maximillians-University Munich, D-80797 Munich, Germany

Title:
[1]"Atom Photon Entanglement"
[2]"Experimental observation of a four photon entangled Dicke state"

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2005
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6th COE Nano Science Forum

Date and TimeFAugust 25, 2005 13:00-16:30

LocationFGraduate School of Engineering Science C419-423 seminar room

LectureF
[1] Mr. Christian Schmid, DC Student, Max Planck Institute fur Quantum Optics (I)
[2] Elham Kashefi, Postdoctoral Fellow, Institute for Quantum Computing
(University of Waterloo)^Junior Research Fellow,
Christ church College (University of Oxford)(II, III)

AbstractF
13:00 I: Four photon Experiments

Four photon experiments in Max Planck Institute for quantum
optics will be reviewed including generation and evaluation of the
4-photon cluster states.

14:00 IIFA universal and fault tolerant model with Pauli measurements

One way model (cluster state or measurement based computing) has recently gained
a lot of attention from both practical and theoretical aspects. However most of the existing
analysis are based on translation of a given circuit into this model. In this talk
I present how one can depart from this view by direct manipulation of graph states and
present a new scheme for fault tolerant computing using only Pauli measurements.
(I will not assume any familiarity with measurement based quantum computing and
will review in the first part of the talk, all the required background. )

15:30 IIIFOn quantum sampling and one-way functions

The existence of one-way functions is one of the most important open problems
in classical computation. It is also well- known that one-way functions have applications in
cryptography. In this talk I will present several candidates for Quantum one way functions
based on hardness of quantum sampling. Furthermore I will present the relation between
existence of quantum one-way function and separation between complexity classes
QMA, QCMA and BQP.

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Osaka University the 21st Century COE Program

Date and TimeFFebruary 17, 2005 13:30-14:30

LocationFGraduate School of Engineering Science cSPQ seminar room

LectureFDr. Adam Miranowicz
(Faculty of Physics, Adam Mickiewicz University, Poznan, Poland)

TitleF"Counterintuitive results on entanglement
@@@@and nonlocality of two-qubit mixed states"

AbstractF
Quantum entanglement is a key resource for quantum information processing but
still its mathematical description is far from completeness. The talk will be devoted to
inconsistent results on quantifying the entanglement and nonlocality of two-qubit
mixed states by standard measures including: the entanglement of formation, the PPT
entanglement cost, geometric measures of entanglement, as well as a degree of
violation of the Bell inequality. It is usually assumed that if one state is more entangled
then the other for one measure than it also must be for all other measures. Violation
of this assumption will be demonstrated for simple physical processes. Moreover, it will be
shown that two-qubit mixed states can be more entangled than two-qubit pure states for
a given value the PPT entanglement cost.

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QOOS
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Osaka University the 21st Century COE Program

Date and TimeFDecember 8, 2004 13:30-14:30

LocationFGraduate School of Engineering Science cSPQ seminar room

LectureFHumiaki Morikoshi@imss Basic Research Labolatories Researcherj

TitleF"Thermodynamical detection of entanglement by Maxwell's demons"

AbstractF
Entanglement is an indispensable resource for quantum information processing. Besides
information processing, what kind of physical processes can exploit entanglement?
In this talk, we will show that we can extract more work from a heat bath via entangled
states than via classically correlated ones in a specific thermodynamical scenario.
In other words, two demons sharing correlated systems can detect entanglement by
local operations and classical communication.

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