Talks

9973 - 9984 of 16890 Results

Homological Product Codes

Sergey Bravyi IBM (United States)

November 27, 2013

PIRSA:13110091

Quantum Information
Insightful supersymmetry

Erich Poppitz University of Toronto

November 27, 2013

PIRSA:13110061

Particle Physics
13/14 PSI - Condensed Matter - Lecture 13

Anushya Chandran Perimeter Institute for Theoretical Physics

Roger Melko University of Waterloo

Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics

November 27, 2013

PIRSA:13110043
13/14 PSI - Quantum Field Theory II - Lecture 13

Francois David CEA Saclay

November 27, 2013

PIRSA:13110024
General Relativity for Cosmology - Lecture 21

Achim Kempf University of Waterloo

November 26, 2013

PIRSA:13110003
Bounding the Elliptope of Quantum Correlations & Proving Separability in Mixed States

Elie Wolfe Perimeter Institute for Theoretical Physics

November 26, 2013

PIRSA:13110092

Quantum Foundations
Classical Space Times from S Matrices

Ira Rothstein Carnegie Mellon University

November 26, 2013

PIRSA:13110053

Particle Physics
BiGravity: from Cosmological Solutions to Dual Galileons

Matteo Fasiello University of Portsmouth

November 26, 2013

PIRSA:13110093

Cosmology
13/14 PSI - Condensed Matter - Lecture 12

Anushya Chandran Perimeter Institute for Theoretical Physics

Roger Melko University of Waterloo

Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics

November 26, 2013

PIRSA:13110042
13/14 PSI - Quantum Field Theory II - Lecture 12

Francois David CEA Saclay

November 26, 2013

PIRSA:13110023
13/14 PSI - Condensed Matter - Lecture 11

Anushya Chandran Perimeter Institute for Theoretical Physics

Roger Melko University of Waterloo

Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics

November 25, 2013

PIRSA:13110041
13/14 PSI - Quantum Field Theory II - Lecture 11

Francois David CEA Saclay

November 25, 2013

PIRSA:13110022

Homological Product Codes

Sergey Bravyi IBM (United States)

November 27, 2013

PIRSA:13110091

Quantum Information

Quantum codes with low-weight stabilizers known as LDPC codes have been actively studied recently due to their potential applications in fault-tolerant quantum computing. However, all families of quantum LDPC codes known to this date suffer from a poor distance scaling limited by the square-root of the code length. This is in a sharp contrast with the classical case where good families of LDPC codes are known that combine constant encoding rate and linear distance. Here we propose the first family of good quantum codes with low-weight stabilizers. The new codes have a constant encoding rate, linear distance, and stabilizers acting on at most square root of n qubits, where n is the code length. For comparison, all previously known families of good quantum codes have stabilizers of linear weight. Our proof combines two techniques: randomized constructions of good quantum codes and the homological product operation from algebraic topology. We conjecture that similar methods can produce good stabilizer codes with stabilizer weight n^a for any a>0. Finally, we apply the homological product to construct new small codes with low-weight stabilizers. This is a joint work with Matthew Hastings.
Insightful supersymmetry

Erich Poppitz University of Toronto

November 27, 2013

PIRSA:13110061

Particle Physics

It has recently been realized that some studies of supersymmetric gauge theories, when properly interpreted, lead to insights whose importance transcends supersymmetry. I will illustrate the insightful nature of supersymmetry by two examples having to do with the microscopic description of the thermal deconfinement transition, in non-supersymmetric pure Yang-Mills theory and in QCD with adjoint fermions. A host of strange ``topological" molecules will be seen to be the major players in the confinement-deconfinement dynamics. Interesting connections between topology, ``condensed-matter" gases of electric and magnetic charges, and attempts to interpret the divergent perturbation series will emerge. Much of the presentation will be aimed at non-experts.
13/14 PSI - Condensed Matter - Lecture 13

Anushya Chandran Perimeter Institute for Theoretical Physics

Roger Melko University of Waterloo

Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics

November 27, 2013

PIRSA:13110043
13/14 PSI - Quantum Field Theory II - Lecture 13

Francois David CEA Saclay

November 27, 2013

PIRSA:13110024
General Relativity for Cosmology - Lecture 21

Achim Kempf University of Waterloo

November 26, 2013

PIRSA:13110003
Bounding the Elliptope of Quantum Correlations & Proving Separability in Mixed States

Elie Wolfe Perimeter Institute for Theoretical Physics

November 26, 2013

PIRSA:13110092

Quantum Foundations

We present a method for determining the maximum possible violation of any linear Bell inequality per quantum mechanics. Essentially this amounts to a constrained optimization problem for an observable’s eigenvalues, but the problem can be reformulated so as to be analytically tractable. This opens the door for an arbitrarily precise characterization of quantum correlations, including allowing for non-random marginal expectation values. Such a characterization is critical when contrasting QM to superficially similar general probabilistic theories. We use such marginal-involving quantum bounds to estimate the volume of all possible quantum statistics in the complete 8-dimensional probability space of the Bell-CHSH scenario, measured relative to both local hidden variable models as well as general no-signaling theories. See arXiv:1106.2169. Time permitting, we’ll also discuss how one might go about trying to prove that a given mixed state is, in fact, not entangled. (The converse problem of certifying non-zero entanglement has received extensive treatment already.) Instead of directly asking if any separable representation exists for the state, we suggest simply checking to see if it “fits” some particular known-separable form. We demonstrate how a surprisingly valuable sufficient separability criterion follows merely from considering a highly-generic separable form. The criterion we generate for diagonally-symmetric mixed states is apparently completely tight, necessary and sufficient. We use integration to quantify the “volume” of states captured by our criterion, and show that it is as large as the volume of states associated with the PPT criterion; this simultaneously proves our criterion to be necessary as well as the PPT criterion to be sufficient, on this family of states. The utility of a sufficient separability criterion is evidenced by categorically rejecting Dicke-model superradiance for entanglement generation schema. See arXiv:1307.5779.
Classical Space Times from S Matrices

Ira Rothstein Carnegie Mellon University

November 26, 2013

PIRSA:13110053

Particle Physics

Progress in calculating S matrix elements have shown that the malicious redundancies in non-linear gauge theories can be circumvented by utilizing unitarity methods in conjunction with BCFW recursion relations. When calculating in this fashion all of the interaction vertices beyond the three point function can be ignored. This simplification is especially useful in gravity which contains an infinite number of such non-linear interactions. It is natural to ask whether off-shell quantities, such as classical solutions, can also be generated using only the three point vertex. In this talk I will show that this is indeed the case by extracting classical solutions to GR from on-hell two to two scattering S-matrix elements. In so doing we will completely circumvent the action as well as the equations of motion. The only inputs will be Lorentz invariance, the existence of a massless spin-two particle and locality. Because of the double copy relation this implies there exists, a yet to be understood, connection between solutions to Yang-Mills theory and Gravity. I will also discuss how this technique can be used to simplify calculations of higher order post-Newtonian corrections to gravitational potentials relevant to the problem of binary inspirals.
BiGravity: from Cosmological Solutions to Dual Galileons

Matteo Fasiello University of Portsmouth

November 26, 2013

PIRSA:13110093

Cosmology

I will present Cosmological FRW Solutions in BiGravity Theories and discuss their stability. After deriving the stability bound, one realizes that in Bigravity (in contradistinction to the FRW massive gravity case) the tension between requirements stemming from stability and those set by observations is resolved. The stability bound can also be derived in the decoupling limit of Bigravity. In this context an intriguing duality between Galilean interactions has emerged.
13/14 PSI - Condensed Matter - Lecture 12

Anushya Chandran Perimeter Institute for Theoretical Physics

Roger Melko University of Waterloo

Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics

November 26, 2013

PIRSA:13110042
13/14 PSI - Quantum Field Theory II - Lecture 12

Francois David CEA Saclay

November 26, 2013

PIRSA:13110023
13/14 PSI - Condensed Matter - Lecture 11

Anushya Chandran Perimeter Institute for Theoretical Physics

Roger Melko University of Waterloo

Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics

November 25, 2013

PIRSA:13110041
13/14 PSI - Quantum Field Theory II - Lecture 11

Francois David CEA Saclay

November 25, 2013

PIRSA:13110022

Title	Date	Collection	Type	Info
Homological Product Codes	2013‑11‑27	Perimeter Institute Quantum Discussions	Scientific Series	View details
Insightful supersymmetry	2013‑11‑27	Colloquium	Scientific Series	View details
13/14 PSI - Condensed Matter - Lecture 13	2013‑11‑27	13/14 PSI - Condensed Matter	Course	View details
13/14 PSI - Quantum Field Theory II - Lecture 13	2013‑11‑27	13/14 PSI - Quantum Field Theory II	Course	View details
General Relativity for Cosmology - Lecture 21	2013‑11‑26	General Relativity for Cosmology - 2013	Course	View details
Bounding the Elliptope of Quantum Correlations & Proving Separability in Mixed States	2013‑11‑26	Quantum Foundations	Scientific Series	View details
Classical Space Times from S Matrices	2013‑11‑26	Particle Physics	Scientific Series	View details
BiGravity: from Cosmological Solutions to Dual Galileons	2013‑11‑26	Cosmology and Gravitation	Scientific Series	View details
13/14 PSI - Condensed Matter - Lecture 12	2013‑11‑26	13/14 PSI - Condensed Matter	Course	View details
13/14 PSI - Quantum Field Theory II - Lecture 12	2013‑11‑26	13/14 PSI - Quantum Field Theory II	Course	View details
13/14 PSI - Condensed Matter - Lecture 11	2013‑11‑25	13/14 PSI - Condensed Matter	Course	View details
13/14 PSI - Quantum Field Theory II - Lecture 11	2013‑11‑25	13/14 PSI - Quantum Field Theory II	Course	View details

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