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Lower bounds for Generalized Quantum Finite Automata

Mark Mercer McGill University
June 04, 2007

PIRSA:07060028
Quantum Information
Quantum Network Engineering

Man-Hong Yung Harvard University
June 04, 2007

PIRSA:07060027
Quantum Information
A Polarization Entangled Photon Source Based on a Modified Sagnac Interferometer

Devin Smith Institute for Quantum Computing (IQC)
June 04, 2007

PIRSA:07060026
Quantum Information
Two concepts of classicality in quantum mechanics

Olaf Dreyer Freelance Consultant
June 04, 2007

PIRSA:07060038
Quantum Foundations
Toward a 5-qubit solid state quantum computer

Martin Laforest Institute for Quantum Computing (IQC)
June 04, 2007

PIRSA:07060025
Quantum Information
Toward a general theory of quantum games

Gus Gutowski Institute for Quantum Computing (IQC)
June 04, 2007

PIRSA:07060024
Quantum Information
Categorizing nonclassical phenomena: the explanatory power of epistemic restrictions and contextuality

Robert Spekkens Perimeter Institute for Theoretical Physics
June 04, 2007

PIRSA:07060037
Quantum Information

Quantum Foundations
Toward a quantum Fourier transform on SU(2).

Richard Low Apple Inc.
June 04, 2007

PIRSA:07060023
Quantum Information
Approximate quantum encryption and entropic security

Frédéric Dupuis McGill University
June 04, 2007

PIRSA:07060022
Quantum Information
Separations of generalized probabilistic theories via their information processing capabilities

Matthew Leifer Chapman University
June 04, 2007

PIRSA:07060033
Quantum Foundations
Practical quantum-key-distribution systems with detector efficiency mismatch: attacks and secret key rates
June 04, 2007

PIRSA:07060021
Quantum Information
Learning about topological quantum memory

Lucy Liuxuan Zhang University of Maryland, College Park
June 04, 2007

PIRSA:07060020
Quantum Information

Lower bounds for Generalized Quantum Finite Automata

Mark Mercer McGill University
June 04, 2007

PIRSA:07060028
Quantum Information
For most variations of Quantum finite automata (QFA), it is an open question to characterize the language recognition power of these machines. We extend several techniques used to obtain lower bounds on Kondacs and Watrous' 1-way Quantum Finite Automata to the case of Nayak's Generalized Quantum Finite Automata (GQFA). A consequence of these results is that the class of languages recognized by GQFAs is not closed under union.
Quantum Network Engineering

Man-Hong Yung Harvard University
June 04, 2007

PIRSA:07060027
Quantum Information
A Polarization Entangled Photon Source Based on a Modified Sagnac Interferometer

Devin Smith Institute for Quantum Computing (IQC)
June 04, 2007

PIRSA:07060026
Quantum Information
A new source of polarization entangled photons is presented based on a bidirectionally pumped spontaneous parametric down-conversion crystal in the loop of a Sagnac interferometer. The source is pumped with a pulsed Ti:SA laser, allowing for high photon pair production rates and the potential for multi-photon experiments. Implementation, detection, and preliminary experimental results will be discussed.
Two concepts of classicality in quantum mechanics

Olaf Dreyer Freelance Consultant
June 04, 2007

PIRSA:07060038
Quantum Foundations
Toward a 5-qubit solid state quantum computer

Martin Laforest Institute for Quantum Computing (IQC)
June 04, 2007

PIRSA:07060025
Quantum Information
Toward a general theory of quantum games

Gus Gutowski Institute for Quantum Computing (IQC)
June 04, 2007

PIRSA:07060024
Quantum Information
Categorizing nonclassical phenomena: the explanatory power of epistemic restrictions and contextuality

Robert Spekkens Perimeter Institute for Theoretical Physics
June 04, 2007

PIRSA:07060037
Quantum Information

Quantum Foundations
Toward a quantum Fourier transform on SU(2).

Richard Low Apple Inc.
June 04, 2007

PIRSA:07060023
Quantum Information
Almost all known superpolynomial quantum speedups over classical algorithms have used the quantum Fourier transform (QFT). Most known applications of the QFT make use of the QFT over abelian groups, including Shor’s well known factoring algorithm [1]. However, the QFT can be generalised to act on non-abelian groups allowing different applications. For example, Kuperberg solves the dihedral hidden subgroup problem in subexponential time using the QFT on the dihedral group. The aim of this research is to construct an efficient QFT on SU(2). Most of the progress in constructing QFTs has come from applying ideas from classical algorithms such as subgroup adapted bases. For example, Moore et al. have applied classical ideas from e.g. to build non-abelian QFTs. Applying these ideas to infinite groups such as SU(2) requires new tools. The function must be sampled or discretised in a way so as to minimise the error. I will present some ideas based on classical algorithms which may lead to a QFT over the group SU(2) for band limited functions. There are problems with making these algorithms unitary that must be addressed and efficient methods for calculating coefficients (cf. the controlled phase gates in the abelian case) must be found.
Approximate quantum encryption and entropic security

Frédéric Dupuis McGill University
June 04, 2007

PIRSA:07060022
Quantum Information
An approximate quantum encryption scheme uses a private key to encrypt a quantum state while leaking only a very small (though non-zero) amount of information to the adversary. Previous work has shown that while we need 2n bits of key to encrypt n qubits exactly, we can get away with only n bits in the approximate case, provided that we know that the state to be encrypted is not entangled with something that the adversary already has in his possession. In this talk I will show a generalization of this result: approximate quantum encryption requires roughly n-t bits of key, where t is a lower bound on the conditional min-entropy of the state to be encrypted given the adversary's prior knowledge. Along the way, I will introduce a quantum version of entropic security and show how the approximate quantum encryption scheme fits within this framework. This is joint work with Simon-Pierre Desrosiers.
Separations of generalized probabilistic theories via their information processing capabilities

Matthew Leifer Chapman University
June 04, 2007

PIRSA:07060033
Quantum Foundations
Practical quantum-key-distribution systems with detector efficiency mismatch: attacks and secret key rates
June 04, 2007

PIRSA:07060021
Quantum Information
Imperfections in devices are inevitable in practice. In this talk, we focus on the imperfection of QKD systems in the detectors, namely that the efficiencies of the detectors are not completely identical. We show some practical attacks that specifically exploit this efficiency mismatch and demonstrate how Eve may obtain some information on the final key if Alice and Bob are unaware of the attack. Also, we discuss the upper and lower bounds on the secret key rates both with and without the assumption of the efficiency mismatch
Learning about topological quantum memory

Lucy Liuxuan Zhang University of Maryland, College Park
June 04, 2007

PIRSA:07060020
Quantum Information
I will introduce Kitaev's suface codes as a block quantum error-correcting code. Recovery procedures will be described in the case of imperfect syndrome measurements. More might be covered if time permits.

Title	Date	Collection	Type	Info
Lower bounds for Generalized Quantum Finite Automata	2007‑06‑04	The Fourth Annual Canadian Quantum Information Students' Conference - 2007	Conference	View details
Quantum Network Engineering	2007‑06‑04	The Fourth Annual Canadian Quantum Information Students' Conference - 2007	Conference	View details
A Polarization Entangled Photon Source Based on a Modified Sagnac Interferometer	2007‑06‑04	The Fourth Annual Canadian Quantum Information Students' Conference - 2007	Conference	View details
Two concepts of classicality in quantum mechanics	2007‑06‑04	Operational Quantum Physics and the Quantum-Classical Contrast - 2007	Conference	View details
Toward a 5-qubit solid state quantum computer	2007‑06‑04	The Fourth Annual Canadian Quantum Information Students' Conference - 2007	Conference	View details
Toward a general theory of quantum games	2007‑06‑04	The Fourth Annual Canadian Quantum Information Students' Conference - 2007	Conference	View details
Categorizing nonclassical phenomena: the explanatory power of epistemic restrictions and contextuality	2007‑06‑04	Operational Quantum Physics and the Quantum-Classical Contrast - 2007	Conference	View details
Toward a quantum Fourier transform on SU(2).	2007‑06‑04	The Fourth Annual Canadian Quantum Information Students' Conference - 2007	Conference	View details
Approximate quantum encryption and entropic security	2007‑06‑04	The Fourth Annual Canadian Quantum Information Students' Conference - 2007	Conference	View details
Separations of generalized probabilistic theories via their information processing capabilities	2007‑06‑04	Operational Quantum Physics and the Quantum-Classical Contrast - 2007		View details
Practical quantum-key-distribution systems with detector efficiency mismatch: attacks and secret key rates	2007‑06‑04	The Fourth Annual Canadian Quantum Information Students' Conference - 2007	Conference	View details
Learning about topological quantum memory	2007‑06‑04	The Fourth Annual Canadian Quantum Information Students' Conference - 2007	Conference	View details

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