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 949 - 960 of 1365

Quantum Computation vs. Firewalls

Daniel Harlow Massachusetts Institute of Technology (MIT)
February 26, 2013

PIRSA:13020138
Quantum Information

Quantum Fields and Strings
12/13 PSI - Quantum Information Review Lecture 6

Andrew Childs University of Waterloo
February 26, 2013

PIRSA:13020116
Quantum Information
Bounding the purification rank of mixed states

Gemma De Las Cuevas Universität Innsbruck
February 25, 2013

PIRSA:13020149
Quantum Information
12/13 PSI - Quantum Information Review Lecture 5

Andrew Childs University of Waterloo
February 25, 2013

PIRSA:13020115
Quantum Information
12/13 PSI - Quantum Information Review Lecture 4

Andrew Childs University of Waterloo
February 22, 2013

PIRSA:13020112
Quantum Information
12/13 PSI - Quantum Information Review Lecture 3

Andrew Childs University of Waterloo
February 21, 2013

PIRSA:13020111
Quantum Information
12/13 PSI - Quantum Information Review Lecture 2

Andrew Childs University of Waterloo
February 20, 2013

PIRSA:13020110
Quantum Information
12/13 PSI - Quantum Information Review Lecture 1

Andrew Childs University of Waterloo
February 19, 2013

PIRSA:13020109
Quantum Information
Random matrices, free probability and quantum information theory

Benoit Collins
January 31, 2013

PIRSA:13010115
Quantum Information
Pinning of Fermionic Occupation Numbers

Christian Schilling ETH Zurich
January 21, 2013

PIRSA:13010105
Quantum Information
Inference of effective quantum models in the asymptotic regime
December 17, 2012

PIRSA:12120042
Quantum Information
Application of conditional independence to gapped quantum many-body systems

Isaac Kim University of California, Davis
December 12, 2012

PIRSA:12120035
Quantum Information

Quantum Computation vs. Firewalls

Daniel Harlow Massachusetts Institute of Technology (MIT)
February 26, 2013

PIRSA:13020138
Quantum Information

Quantum Fields and Strings
12/13 PSI - Quantum Information Review Lecture 6

Andrew Childs University of Waterloo
February 26, 2013

PIRSA:13020116
Quantum Information
Bounding the purification rank of mixed states

Gemma De Las Cuevas Universität Innsbruck
February 25, 2013

PIRSA:13020149
Quantum Information
A mixed state can be expressed as a sum of D tensor product matrices, where D is its operator Schmidt rank, or as the result of a purification with a purifying state of Schmidt rank D', where D' is its purification rank. The question whether D' can be upper bounded by D is important theoretically (to establish a description of mixed states with tensor networks), as well as numerically (as the first decomposition is more efficient, but the second one guarantees positive-semidefiniteness after truncation). Here we show that no upper bounds of the purification rank that depend only on operator Schmidt rank exist, but provide upper bounds that also depend on the number of eigenvalues. In addition, we formulate the approximation problem as a Semidefinite Program.
Joint work with N. Schuch, D. Perez-Garcia, and J. I. Cirac.
12/13 PSI - Quantum Information Review Lecture 5

Andrew Childs University of Waterloo
February 25, 2013

PIRSA:13020115
Quantum Information
12/13 PSI - Quantum Information Review Lecture 4

Andrew Childs University of Waterloo
February 22, 2013

PIRSA:13020112
Quantum Information
12/13 PSI - Quantum Information Review Lecture 3

Andrew Childs University of Waterloo
February 21, 2013

PIRSA:13020111
Quantum Information
12/13 PSI - Quantum Information Review Lecture 2

Andrew Childs University of Waterloo
February 20, 2013

PIRSA:13020110
Quantum Information
12/13 PSI - Quantum Information Review Lecture 1

Andrew Childs University of Waterloo
February 19, 2013

PIRSA:13020109
Quantum Information
Random matrices, free probability and quantum information theory

Benoit Collins
January 31, 2013

PIRSA:13010115
Quantum Information
In quantum information theory, random techniques have proven to be very useful. For example, many questions related to the problem of the additivity of entropies of quantum channels rely on fine properties of concentration of measure. In this talk, I will show that very different techniques of random matrix theory can complement quite efficiently more classical random techniques. I will spend some time on discussing the Weingarten calculus approach, and the operator norm approach. Both techniques have been initially used in free probability theory, and I will give some new applications of these techniques to quantum information theory.
Pinning of Fermionic Occupation Numbers

Christian Schilling ETH Zurich
January 21, 2013

PIRSA:13010105
Quantum Information
The problem of determining and describing the family of 1-particle reduced density operators (1-RDO) arising from N-fermion pure states (viapartial trace) is known as the fermionic quantum marginal problem. We present its solution, a multitude of constraints on the eigenvalues of the 1-RDO, generalizing the Pauli exclusion principle. To explore the relevance of these constraints we study an analytically solvable model of N fermions in a harmonic potential and determine the spectral `trajectory' corresponding to the ground state as function of the fermion-fermion interaction strength.Intriguingly, we find that the occupation numbers are almost, but not exactly, pinned to the boundary of the allowed region (quasi-pinned). Our findings suggest a generalization of the Hartree-Fock approximation.

see also: http://arxiv.org/abs/1210.5531
Inference of effective quantum models in the asymptotic regime
December 17, 2012

PIRSA:12120042
Quantum Information
In this talk I will sketch a project which aims at the design of systematic and efficient procedures to infer quantum models from measured data. Progress in experimental control have enabled an increasingly fine tuned probing of the quantum nature of matter, e.g., in superconducting qubits. Such experiments have shown that we not always have a good understanding of how to model the experimentally performed measurements via POVMs. It turns out that the ad hoc postulation of POVMs can lead to inconsistencies. For example, when doing asymptotic state tomography via linear inversion, one sometimes recovers density operators which are significantly not positive semidefinite. Assuming the asymptotic regime, we suggest an alternative procedure where we do not make a priori assumptions on the quantum model, i.e., on the Hilbert space dimension, the prepared states or the measured POVMs. In other words, we simultaneously estimate the dimension of the underlying Hilbert space, the quantum states and the POVMs. We are guided by Occam's razor, i.e., we search for the minimal quantum model consistent with the data.
Application of conditional independence to gapped quantum many-body systems

Isaac Kim University of California, Davis
December 12, 2012

PIRSA:12120035
Quantum Information
It is widely known in the quantum information community that the states that satisfy strong subadditivity of entropy with equality have the form of quantum Markov chain. Based on a recent strengthening of strong subadditivity of entropy, I will describe how such structure can be exploited in the studies of gapped quantum many-body system. In particular, I will describe a diagrammatic trick to i) give a quantitative statement about the locality of entanglement spectrum ii) perturbatively bound changes of topological entanglement entropy under generic perturbation.

Title	Speaker(s)	Date	Talk Type	Info link
Quantum Computation vs. Firewalls	Daniel Harlow	2013-02-26	Scientific Series	View details
12/13 PSI - Quantum Information Review Lecture 6	Andrew Childs	2013-02-26	Course	View details
Bounding the purification rank of mixed states	Gemma De Las Cuevas	2013-02-25	Scientific Series	View details
12/13 PSI - Quantum Information Review Lecture 5	Andrew Childs	2013-02-25	Course	View details
12/13 PSI - Quantum Information Review Lecture 4	Andrew Childs	2013-02-22	Course	View details
12/13 PSI - Quantum Information Review Lecture 3	Andrew Childs	2013-02-21	Course	View details
12/13 PSI - Quantum Information Review Lecture 2	Andrew Childs	2013-02-20	Course	View details
12/13 PSI - Quantum Information Review Lecture 1	Andrew Childs	2013-02-19	Course	View details
Random matrices, free probability and quantum information theory	Benoit Collins	2013-01-31	Scientific Series	View details
Pinning of Fermionic Occupation Numbers	Christian Schilling	2013-01-21	Scientific Series	View details
Inference of effective quantum models in the asymptotic regime		2012-12-17	Scientific Series	View details
Application of conditional independence to gapped quantum many-body systems	Isaac Kim	2012-12-12	Scientific Series	View details

Quantum Information

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