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 889 - 900 of 1338

Characterizing topological spin liquids using PEPS

Norbert Schuch
Max Planck Institute for Gravitational Physics - Albert Einstein Institute (AEI)
May 09, 2013

PIRSA:13050044
Quantum Information
Emergence and Entanglement in Matrix Product States

Frank Verstraete
Ghent University
May 09, 2013

PIRSA:13050043
Quantum Information
Characterizing topological order form a microscopic lattice Hamiltonian

Lukasz Cincio
Los Alamos National Laboratory
May 09, 2013

PIRSA:13050042
Quantum Information

Condensed Matter
Topological Order with a Twist: Ising Anyons from an Abelian Model

Hector Bombin
PsiQuantum Corp.
May 06, 2013

PIRSA:13050024
Quantum Information
From Pauli's Principle to Fermionic Entanglement

Matthias Christandl
ETH Zurich
May 03, 2013

PIRSA:13050005
Quantum Information

Quantum Foundations
Tensor Networks: an Overview

Lukasz Cincio
Los Alamos National Laboratory
April 25, 2013

PIRSA:13040131
Quantum Information
Continuous-variable entanglement distillation and non-commutative central limit theorems

Earl Campbell
University of Sheffield
April 15, 2013

PIRSA:13040122
Quantum Information
12/13 PSI - Explorations on Quantum Information Lecture 14

David Cory
Institute for Quantum Computing (IQC)
April 05, 2013

PIRSA:13040037
Quantum Information
12/13 PSI - Explorations on Quantum Information Lecture 13

David Cory
Institute for Quantum Computing (IQC)
April 04, 2013

PIRSA:13040036
Quantum Information
Quantum key expansion based on entanglement-assisted quantum LDPC codes

Todd Brun
University of Southern California
April 03, 2013

PIRSA:13040108
Quantum Information
12/13 PSI - Explorations on Quantum Information Lecture 12

David Cory
Institute for Quantum Computing (IQC)
April 03, 2013

PIRSA:13040035
Quantum Information
12/13 PSI - Explorations on Quantum Information Lecture 11

David Cory
Institute for Quantum Computing (IQC)
April 02, 2013

PIRSA:13040034
Quantum Information

Characterizing topological spin liquids using PEPS

Norbert Schuch
Max Planck Institute for Gravitational Physics - Albert Einstein Institute (AEI)
May 09, 2013

PIRSA:13050044
Quantum Information
Projected Entangled Pair States (PEPS) provide a local description of correlated many-body states. I will discuss how PEPS can be used to characterize topological spin liquids, in particular Resonating Valence Bond states. On the one hand, I will show how the symmetries in the local PEPS description allow to identify that these states appear as topologically degenerate ground states of local Hamiltonians. On the other hand, I will discuss how from exact diagonalization of the transfer operator one can extract both the topological order and the spin liquid nature of the ground state.
Emergence and Entanglement in Matrix Product States

Frank Verstraete
Ghent University
May 09, 2013

PIRSA:13050043
Quantum Information
Characterizing topological order form a microscopic lattice Hamiltonian

Lukasz Cincio
Los Alamos National Laboratory
May 09, 2013

PIRSA:13050042
Quantum Information

Condensed Matter
In this talk I will show how to obtain a detailed characterization of the emergent topological order starting from microscopic Hamiltonian on a two dimensional lattice. A key step is to obtain a tensor network representation for a complete set of ground states of the Hamiltonian, ﬁrst on an inﬁnite cylinder and then on a ﬁnite torus. As an application of the method I will study lattice Hamiltonians that give rise to selected anyon models, namely chiral semion, Ising as well as Z_3 and Z_5 models.
Topological Order with a Twist: Ising Anyons from an Abelian Model

Hector Bombin
PsiQuantum Corp.
May 06, 2013

PIRSA:13050024
Quantum Information
Anyon models can be symmetric under some permutations of their topological charges. One can then conceive topological defects that, under monodromy, transform anyons according to a symmetry. We study the realization of such defects in the toric code model, showing that a process where defects are braided and fused has the same outcome as if they were Ising anyons.
From Pauli's Principle to Fermionic Entanglement

Matthias Christandl
ETH Zurich
May 03, 2013

PIRSA:13050005
Quantum Information

Quantum Foundations
The Pauli exclusion principle is a constraint on the natural occupation numbers of fermionic states. It has been suspected for decades, and only proved very recently, that there is a multitude of further constraints on these numbers, generalizing the Pauli principle. Surprisingly, these constraints are linear: they cut out a geometric object known as a polytope. This is a beautiful mathematical result, but are there systems whose physics is governed by these constraints? In order to address this question, we studied a system of a few fermions connected by springs. As we varied the spring constant, the occupation numbers moved within the polytope. The path they traced hugs very close to the boundary of the polytope, suggesting that the generalized constraints affect the system. I will mention the implications of these findings for the structure of few-fermion ground states and then discuss the relation between the geometry of the polytope and different types of fermionic entanglement.
Tensor Networks: an Overview

Lukasz Cincio
Los Alamos National Laboratory
April 25, 2013

PIRSA:13040131
Quantum Information
Tensor network algorithms provide highly competitive tools for analyzing ground state properties of quantum lattice models in one and two spatial dimensions. The most notable examples involve matrix product states, projected entangled pair states and multiscale entanglement renormalization ansatz. The key underlying idea of all the approaches is to decompose a quantum many-body state into a carefully chosen network of tensors.
In this talk I will give an introduction to the subject and show how tensor networks can be used to characterize topological order.
Continuous-variable entanglement distillation and non-commutative central limit theorems

Earl Campbell
University of Sheffield
April 15, 2013

PIRSA:13040122
Quantum Information
Entanglement distillation transforms weakly entangled noisy states into highly entangled states, a primitive to be used in quantum repeater schemes and other protocols designed for quantum communication and key distribution. In this work, we present a comprehensive framework for continuous-variable entanglement distillation schemes that convert noisy non-Gaussian states into Gaussian ones in many iterations of the protocol. Instances of these protocols include the recursive Gaussifier protocol and the pumping Gaussifier protocol. The flexibility of these protocols give rise to several beneficial trade-offs related to success probabilities or memory requirements that can be adjusted to reflect experimental specifics. Despite these protocols involving measurements, we relate the convergence in this protocols to new instances of non-commutative central limit theorems. Implications of the findings for quantum repeater schemes are discussed.
12/13 PSI - Explorations on Quantum Information Lecture 14

David Cory
Institute for Quantum Computing (IQC)
April 05, 2013

PIRSA:13040037
Quantum Information
12/13 PSI - Explorations on Quantum Information Lecture 13

David Cory
Institute for Quantum Computing (IQC)
April 04, 2013

PIRSA:13040036
Quantum Information
Quantum key expansion based on entanglement-assisted quantum LDPC codes

Todd Brun
University of Southern California
April 03, 2013

PIRSA:13040108
Quantum Information
Quantum key distribution protocols can be based on quantum error correcting codes, where the structure of the code determines the post processing protocol applied to a raw key produced by BB84 or a similar scheme. Luo and Devetak showed that basing a similar protocol on entanglement-assisted quantum error-correcting codes (EAQECCs) leads to quantum key expansion (QKE) protocols, where some amount of previously shared secret key is used as a seed in the post-processing stage to produce a larger secret key. One of the promising aspects of EAQECCs is that they can be constructed from classical linear codes that don't satisfy the dual-containing property, which among other things allows the use of low density parity-check (LDPC) codes with girth greater than 4, for which the iterative decoding algorithm has better performance. We looked into QKE based on a family of EAQECCs generated by classical finite geometry (FG) LDPC codes. Very efficient iterative decoders exist for these codes, and they were shown by Hsieh, Yen and Hau to produce quantum LDPC codes that require very little entanglement. We modify the original QKE protocol to detect bad code blocks without the consumption of secret key when the protocol fails. This allows us to greatly reduce the bit error rate of the key, at the cost of a minor reduction in the net key production rate, but without increasing the consumption rate of pre-shared key. Numerical simulations for the family of FG LDPC codes show that this improved QKE protocol has a good net key production rate even at relatively high error rates, for appropriate code choices.
12/13 PSI - Explorations on Quantum Information Lecture 12

David Cory
Institute for Quantum Computing (IQC)
April 03, 2013

PIRSA:13040035
Quantum Information
12/13 PSI - Explorations on Quantum Information Lecture 11

David Cory
Institute for Quantum Computing (IQC)
April 02, 2013

PIRSA:13040034
Quantum Information

Title	Speaker(s)	Date	Talk Type	Info link
Characterizing topological spin liquids using PEPS	Norbert Schuch	2013-05-09	Conference	View details
Emergence and Entanglement in Matrix Product States	Frank Verstraete	2013-05-09	Conference	View details
Characterizing topological order form a microscopic lattice Hamiltonian	Lukasz Cincio	2013-05-09	Conference	View details
Topological Order with a Twist: Ising Anyons from an Abelian Model	Hector Bombin	2013-05-06	Conference	View details
From Pauli's Principle to Fermionic Entanglement	Matthias Christandl	2013-05-03	Scientific Series	View details
Tensor Networks: an Overview	Lukasz Cincio	2013-04-25	Conference	View details
Continuous-variable entanglement distillation and non-commutative central limit theorems	Earl Campbell	2013-04-15	Scientific Series	View details
12/13 PSI - Explorations on Quantum Information Lecture 14	David Cory	2013-04-05	Course	View details
12/13 PSI - Explorations on Quantum Information Lecture 13	David Cory	2013-04-04	Course	View details
Quantum key expansion based on entanglement-assisted quantum LDPC codes	Todd Brun	2013-04-03	Scientific Series	View details
12/13 PSI - Explorations on Quantum Information Lecture 12	David Cory	2013-04-03	Course	View details
12/13 PSI - Explorations on Quantum Information Lecture 11	David Cory	2013-04-02	Course	View details

Quantum Information

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