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 1153 - 1164 of 1242

Towards the Production of Entangled Photon Pairs in Optical Fiber via Four-Wave Mixing

Joshua Slater University of Calgary
June 02, 2007

PIRSA:07060012
Quantum Information
Distributed phase reference schemes for QKD: Explicit attacks and security considerations

Cyril Branciard Université de Genève
June 02, 2007

PIRSA:07060011
Quantum Information
An Introduction to Decoherence-Free Subspaces

Martin Laforest Institute for Quantum Computing (IQC)
June 02, 2007

PIRSA:07060003
Quantum Information
Information Flow in the Heisenberg Picture

Cédric Bény Leibniz University Hannover
June 02, 2007

PIRSA:07060009
Quantum Information
Quantum Mechanics in Phase Space
June 02, 2007

PIRSA:07060008
Quantum Information
An Introduction to One-Way Patterns
June 01, 2007

PIRSA:07060007
Quantum Information
Cluster State Quatum Computing in Optical Fibres

Yasaman Soudagar Polytechnique Montreal
June 01, 2007

PIRSA:07060006
Quantum Information
A New Protocol for Loss-Tolerant Quantum Coin Tossing
June 01, 2007

PIRSA:07060005
Quantum Information
Degradability of Bosonic Gaussian Channels

Filippo Caruso Scuola Normale Superiore di Pisa
June 01, 2007

PIRSA:07060004
Quantum Information
Subsystem Quantum Error Correcting Codes

Andrea Casaccino University of Siena
June 01, 2007

PIRSA:07060029
Quantum Information
Single Photon Source on a Breadboard

Erwann Bocquillon Institute for Quantum Computing (IQC)
June 01, 2007

PIRSA:07060002
Quantum Information
On Connections between machine learning and quantum information processing

Sebastien Gambs Institute for Quantum Computing (IQC)
June 01, 2007

PIRSA:07060001
Quantum Information

Towards the Production of Entangled Photon Pairs in Optical Fiber via Four-Wave Mixing

Joshua Slater University of Calgary
June 02, 2007

PIRSA:07060012
Quantum Information
Previous experiments on the production of entangled photon pairs directly in optical fiber via four-wave mixing (FWM) have used a single pump laser and produced signal and idler photons with similar wavelengths. We will present the first results of our investigation into the production of widely separated entangled photon pairs via FWM in optical fiber using multiple pump lasers also at widely separated wavelengths. This source will have important applications in quantum cryptography and computation. As fiber optic and free space quantum communication networks require photons at different wavelengths (1550 nm and around 800 respectively) this source will make hybrid quantum cryptography networks achievable and could also be used as a heralded optical fiber source of single photons.
Distributed phase reference schemes for QKD: Explicit attacks and security considerations

Cyril Branciard Université de Genève
June 02, 2007

PIRSA:07060011
Quantum Information
"Distributed phase reference schemes are a new class of protocols for Quantum Key Distribution, in which the quantum signals have overall phase-relationships to each other. This is expected to protect against some loss-related attacks. However, proving the full security of these schemes is a new challenge for theorists, as one can no longer identify individual signals (such as qubits in BB84, for instance), and so the security proof techniques do not apply directly.In this talk I will present two such protocols (the Differential Phase Shift and the Coherent One Way protocols). Their ""unconditionnal security"" has not been proven yet, but I will present some specific attacks on these schemes, which give us upper bounds for the security, as well as a ""feeling"" on how these schemes should perform."
An Introduction to Decoherence-Free Subspaces

Martin Laforest Institute for Quantum Computing (IQC)
June 02, 2007

PIRSA:07060003
Quantum Information
Information Flow in the Heisenberg Picture

Cédric Bény Leibniz University Hannover
June 02, 2007

PIRSA:07060009
Quantum Information
Quantum Mechanics in Phase Space
June 02, 2007

PIRSA:07060008
Quantum Information
Many authors have proposed what are known as "phase-space" or "classical" representations of quantum mechanics. A unifying framework is given which illustrates the relationship among these various theories. Examples relevant to quantum computing will be given.
An Introduction to One-Way Patterns
June 01, 2007

PIRSA:07060007
Quantum Information
The one-way measurement model is a model of quantum computation which is intriguing for its' potential as a means of implementing quantum computers, but also for theoretical purposes for the different way in which it allows quantum operations to be described. Instead of a sequence of unitary gates on an array of ``wires'', operations are described in terms of emph{patterns}, consisting of a graph of entanglement relations on a set of qubits, together with a collection of measurement angles for these qubits (except possibly for a subset which will support a final quantum state). In this introductory talk, I describe the relationship between patterns in the one-way measurement model to quantum circuits, and explore patterns which represent unitary operations but which emph{don't} have direct analogues in the circuit model.
Cluster State Quatum Computing in Optical Fibres

Yasaman Soudagar Polytechnique Montreal
June 01, 2007

PIRSA:07060006
Quantum Information
In this presentation I will briefly explain the cluster state model of quantum computing. Then will talk about a scheme that uses polarization and time-bin degrees of freedom of photons in optical fibres for the optical realization of this model. We are currently working on the implementation of this scheme in our lab.
A New Protocol for Loss-Tolerant Quantum Coin Tossing
June 01, 2007

PIRSA:07060005
Quantum Information
Quantum coin tossing is a cryptographic task in which two parties, Alice and Bob, wish to generate a shared random bit but do not necessarily trust each other. This task is completely impossible to realize with classical asynchronous communication but becomes at least partially feasible when quantum communication is also available. The best quantum protocol known so far, due to Ambainis, uses qutrits and is near optimal in the sense that either party can bias the outcome with at most a 75% probability of success. However, when the transmission of the link is below 50%, Ambainis' protocol can be easily broken by a cheating Bob. This problem arises whenever there exists a conclusive measurement allowing Bob to obtain with certainty, although with a probability less than one, relevant information about the state sent by Alice. In this talk, we will present a new protocol for quantum coin tossing that does not suffer from this weakness and, as a consequence, is loss-tolerant. We discuss possible attacks and argue that the protocol is secure. Technologically, the implementation of this protocol is no more difficult than implementing entangled quantum key distribution with qubits. This is joint work with Guido Berlin, Gilles Brassard and Nicolas Godbout.
Degradability of Bosonic Gaussian Channels

Filippo Caruso Scuola Normale Superiore di Pisa
June 01, 2007

PIRSA:07060004
Quantum Information
The notion of weak-degradability of quantum channels is introduced by generalizing the degradability definition given by Devetak and Shor. Exploiting the unitary equivalence with beam-splitter/amplifier channels we then prove that a large class of one-mode Bosonic Gaussian channels are either weakly degradable or anti-degradable. In the latter case this implies that their quantum capacity Q is null. In the former case instead, this allows us to establish the additivity of the coherent information for those maps which admit unitary representation with single-mode pure environment.
Subsystem Quantum Error Correcting Codes

Andrea Casaccino University of Siena
June 01, 2007

PIRSA:07060029
Quantum Information
The essential insight of quantum error correction was that quantum information can be protected by suitably encoding this quantum information across multiple independently erred quantum systems. Recently it was realized that, since the most general method for encoding quantum information is to encode it into a subsystem, there exists a novel form of quantum error correction beyond the traditional quantum error correcting subspace codes. These new quantum error correcting subsystem codes differ from subspace codes in that their quantum correcting routines can be considerably simpler than related subspace codes. Here we present a class of quantum error correcting subsystem codes constructed from two classical linear codes. These codes are the subsystem versions of the quantum error correcting subspace codes which are generalizations of Shor’s original quantum error correcting subspace codes. For every Shor-type code, the codes we present give a considerable savings in the number of stabilizer measurements needed in their error recovery routines.
Single Photon Source on a Breadboard

Erwann Bocquillon Institute for Quantum Computing (IQC)
June 01, 2007

PIRSA:07060002
Quantum Information
In quantum information, one can prove that a secure quantum cryptography channel based on photon key distribution requires reliable single photon sources. If not, a potential eavesdropper may be able to get information using the extra photons. Current sources are based on either attenuated laser beams, which may produce randomly 2 or even more photons at a time following a poissonian statistics, or either based on two level-systems providing single photon sources often requiring cooling or complex set-ups.The goal of our experiment is to provide an easy, robust and compact single photon source using nonlinear optics (parametric down-conversion). We want to study its statistics and compare it to other photon sources. We could use this heralded single photon source to create a quantum communication channel.
On Connections between machine learning and quantum information processing

Sebastien Gambs Institute for Quantum Computing (IQC)
June 01, 2007

PIRSA:07060001
Quantum Information

Title	Speaker(s)	Date	Talk Type	Info link
Towards the Production of Entangled Photon Pairs in Optical Fiber via Four-Wave Mixing	Joshua Slater	2007-06-02	Conference	View details
Distributed phase reference schemes for QKD: Explicit attacks and security considerations	Cyril Branciard	2007-06-02	Conference	View details
An Introduction to Decoherence-Free Subspaces	Martin Laforest	2007-06-02	Conference	View details
Information Flow in the Heisenberg Picture	Cédric Bény	2007-06-02	Conference	View details
Quantum Mechanics in Phase Space		2007-06-02	Conference	View details
An Introduction to One-Way Patterns		2007-06-01	Conference	View details
Cluster State Quatum Computing in Optical Fibres	Yasaman Soudagar	2007-06-01	Conference	View details
A New Protocol for Loss-Tolerant Quantum Coin Tossing		2007-06-01	Conference	View details
Degradability of Bosonic Gaussian Channels	Filippo Caruso	2007-06-01	Conference	View details
Subsystem Quantum Error Correcting Codes	Andrea Casaccino	2007-06-01	Conference	View details
Single Photon Source on a Breadboard	Erwann Bocquillon	2007-06-01	Conference	View details
On Connections between machine learning and quantum information processing	Sebastien Gambs	2007-06-01	Conference	View details

Quantum Information

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