Quantum Information

Quantum mechanics redefines information and its fundamental properties. Researchers at Perimeter Institute work to understand the properties of quantum information and study which information processing tasks are feasible, and which are infeasible or impossible. This includes research in quantum cryptography, which studies the trade-off between information extraction and disturbance, and its applications. It also includes research in quantum error correction, which involves the study of methods for protecting information against decoherence. Another important side of the field is studying the application of quantum information techniques and insights to other areas of physics, including quantum foundations and condensed matter.

Displaying 1249 - 1260 of 1357

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
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
Toward a quantum Fourier transform on SU(2).

Richard Low Apple Inc.
June 04, 2007

PIRSA:07060023
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
Approximate quantum encryption and entropic security

Frédéric Dupuis McGill University
June 04, 2007

PIRSA:07060022
Quantum Information
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
Free Space Quantum Key Distribution and its Implementation with a Polarization-Entangled Parametric Down Conversion Source

Christopher Erven Institute for Quantum Computing (IQC)
June 03, 2007

PIRSA:07060050
Quantum Information
Symmetric extendibility of quantum states

Geir Myhr Institute for Quantum Computing (IQC)
June 03, 2007

PIRSA:07060019
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.
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
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.
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
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.
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.
Free Space Quantum Key Distribution and its Implementation with a Polarization-Entangled Parametric Down Conversion Source

Christopher Erven Institute for Quantum Computing (IQC)
June 03, 2007

PIRSA:07060050
Quantum Information
Symmetric extendibility of quantum states

Geir Myhr Institute for Quantum Computing (IQC)
June 03, 2007

PIRSA:07060019
Quantum Information
Imagine that Alice and Bob share a quantum state, from which they want to distill something useful like entanglement or secret key. For this they need to communicate classically and they want to do this by one way communication from Alice to Bob. For some states, it might happen that the state is a part of a tripartite state shared with Charlie, which is invariant if Bob's and Charlie's systems are switched. Such a state is called a symmetric extension, and if it exists Alice and Bob have no chance of distilling key or entanglement by one way communication. I will present some results characterizing which quantum states have symmetric extension.

Title	Speaker(s)	Date	Talk Type	Info link
Lower bounds for Generalized Quantum Finite Automata	Mark Mercer	2007-06-04	Conference	View details
Quantum Network Engineering	Man-Hong Yung	2007-06-04	Conference	View details
A Polarization Entangled Photon Source Based on a Modified Sagnac Interferometer	Devin Smith	2007-06-04	Conference	View details
Toward a 5-qubit solid state quantum computer	Martin Laforest	2007-06-04	Conference	View details
Toward a general theory of quantum games	Gus Gutowski	2007-06-04	Conference	View details
Toward a quantum Fourier transform on SU(2).	Richard Low	2007-06-04	Conference	View details
Categorizing nonclassical phenomena: the explanatory power of epistemic restrictions and contextuality	Robert Spekkens	2007-06-04	Conference	View details
Approximate quantum encryption and entropic security	Frédéric Dupuis	2007-06-04	Conference	View details
Practical quantum-key-distribution systems with detector efficiency mismatch: attacks and secret key rates		2007-06-04	Conference	View details
Learning about topological quantum memory	Lucy Liuxuan Zhang	2007-06-04	Conference	View details
Free Space Quantum Key Distribution and its Implementation with a Polarization-Entangled Parametric Down Conversion Source	Christopher Erven	2007-06-03	Conference	View details
Symmetric extendibility of quantum states	Geir Myhr	2007-06-03	Conference	View details

Quantum Information

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