Talks

9613 - 9624 of 16758 Results

Probabilistic protocols in quantum information

Joshua Combes University of Colorado Boulder

February 13, 2014

PIRSA:14020138

Quantum Information
Firewall evasion by quantum gravity

Ted Jacobson University of Maryland, College Park

February 13, 2014

PIRSA:14020136

Quantum Gravity
Are non-Fermi-liquids stable to pairing?

Max Metlitski Massachusetts Institute of Technology (MIT) - Department of Physics

February 13, 2014

PIRSA:14020143
On null singularities in general relativity

Mihalis Dafermos Princeton University

February 13, 2014

PIRSA:14020133

Strong Gravity
Gauging symmetry of 2D topological phases

Zhenghan Wang Microsoft Corporation

February 13, 2014

PIRSA:14020125
13/14 PSI - Cosmology Review - Lecture 12

Latham Boyle University of Edinburgh

February 13, 2014

PIRSA:14020101
Incoherent metals

Brian Swingle Brandeis University

February 13, 2014

PIRSA:14020124
13/14 PSI - String Theory Review - Lecture 13

Davide Gaiotto Perimeter Institute for Theoretical Physics

February 13, 2014

PIRSA:14020033
Interacting electronic topological insulators in three dimensions

Senthil Todadri Massachusetts Institute of Technology (MIT) - Department of Physics

February 13, 2014

PIRSA:14020123
Chiral spin liquid and emergent anyons in a Kagome lattice Mott insulator

Guifre Vidal Alphabet (United States)

Lukasz Cincio Los Alamos National Laboratory

February 13, 2014

PIRSA:14020122
13/14 PSI - Condensed Matter Review - Lecture 13

Alioscia Hamma University of Naples Federico II

February 13, 2014

PIRSA:14020106
Applications of Information Theory in Direct Sum and Direct Product Problems

February 12, 2014

PIRSA:14020142

Quantum Information

Probabilistic protocols in quantum information

Joshua Combes University of Colorado Boulder

February 13, 2014

PIRSA:14020138

Quantum Information

Probabilistic protocols in quantum information are an attempt to improve performance by occasionally reporting a better result than could be expected from a deterministic protocol. Here we show that probabilistic protocols can never improve performance beyond the quantum limits on the corresponding deterministic protocol. To illustrate this result we examine three common probabilistic protocols: probabilistic amplification, weak value amplification, and probabilistic metrology. In each of these protocols we show explicitly that the optimal deterministic protocol is better than the corresponding probabilistic protocol when the probabilistic nature of the protocol is correctly accounted for.
Firewall evasion by quantum gravity

Ted Jacobson University of Maryland, College Park

February 13, 2014

PIRSA:14020136

Quantum Gravity

It has been argued that if black hole evaporation is a unitary quantum process, then a black hole horizon must be cloaked by a "firewall", i.e. a highly excited state of local quantum fields. This reasoning is based on factorizing the Hilbert space into interior and exterior degrees of freedom. Such factorization ignores the Wheeler-deWitt constraint equation, which arises from the diffeomorphism invariance of quantum gravity. I will argue that this constraint evades the firewall.
Are non-Fermi-liquids stable to pairing?

Max Metlitski Massachusetts Institute of Technology (MIT) - Department of Physics

February 13, 2014

PIRSA:14020143

States of matter with a sharp Fermi-surface but no well-defined Landau
quasiparticles are expected to arise in a number of physical systems.
Examples include i) quantum critical points associated with the onset
of order in metals, ii) the spinon Fermi-surface (U(1) spin-liquid)
state of a Mott insulator and iii) the Halperin-Lee-Read composite
fermion charge liquid state of a half-filled Landau level. In this
talk, I will use renormalization group techniques to investigate
possible instabilities of such non-Fermi-liquids to pairing. I will
show that for a large class of phase transitions in metals, the
attractive interaction mediated by order parameter fluctuations always
leads to a superconducting instability, which preempts the
non-Fermi-liquid effects. On the other hand, the spinon Fermi-surface
and the Halperin-Lee-Read states are stable against pairing for a
sufficiently weak attractive short-range interaction. However, once
the strength of attraction exceeds a critical value, pairing sets in.
I will describe the ensuing quantum phase transition between i) the
U(1) and the Z_2 spin-liquid states, and ii) the Halperin-Lee-Read and
Moore-Read states.
On null singularities in general relativity

Mihalis Dafermos Princeton University

February 13, 2014

PIRSA:14020133

Strong Gravity

This talk will discuss the formation, structure and interaction of null singularities for
the Einstein equations, as well as what this all means for the singular boundary
of generic space times within black hole regions.
Gauging symmetry of 2D topological phases

Zhenghan Wang Microsoft Corporation

February 13, 2014

PIRSA:14020125

I will discuss the mathematical framework for gauging a local unitary finite group symmetry of a 2D topological phase of matter.
13/14 PSI - Cosmology Review - Lecture 12

Latham Boyle University of Edinburgh

February 13, 2014

PIRSA:14020101
Incoherent metals

Brian Swingle Brandeis University

February 13, 2014

PIRSA:14020124

I'll talk about some work in progress concerning the topic of metals which have no coherent quasiparticles. In particular, I'll compare and contrast the ubiquitous near horizon AdS2 region appearing in holographic models with a phase of matter called the spin incoherent luttinger liquid. By analyzing the structure of entanglement and correlations, we will find many similarities between these two states of matter. An interpretation of some incoherent metals as describing intermediate scale renormalization group fixed poins with an infinite number of relevant directions will also be discussed.
13/14 PSI - String Theory Review - Lecture 13

Davide Gaiotto Perimeter Institute for Theoretical Physics

February 13, 2014

PIRSA:14020033
Interacting electronic topological insulators in three dimensions

Senthil Todadri Massachusetts Institute of Technology (MIT) - Department of Physics

February 13, 2014

PIRSA:14020123

I will review recent progress in describing interacting electronic topological insulators/superconductors in three dimensions. The focus will be on Symmetry Protected Topological (SPT) phases of electronic systems with charge conservation and time reversal. I will argue that the well known Z2 classification of free fermion insulators with this important symmetry generalizes to a Z2^3 classification in the presence of interactions. I will describe the experimental fingerprints and other physical properties of these states. If time permits, I will describe results on the classification and properties of 3d electronic SPT states with various other physically relevant symmetries.
Chiral spin liquid and emergent anyons in a Kagome lattice Mott insulator

Guifre Vidal Alphabet (United States)

Lukasz Cincio Los Alamos National Laboratory

February 13, 2014

PIRSA:14020122

Topological phases in frustrated quantum spin systems have fascinated researchers for decades. One of the earliest proposals for such a phase was the chiral spin liquid put forward by Kalmeyer and Laughlin in 1987 as the bosonic analogue of the fractional quantum Hall effect. Elusive for many years, recent times have finally seen a number of models that realize this phase. However, these models are somewhat artificial and unlikely to be found in realistic materials.
Here, we take an important step towards the goal of finding a chiral spin liquid in nature by examining a physically motivated model for a Mott insulator on the Kagome lattice with broken time-reversal symmetry. We first provide a theoretical justification for the emergent chiral spin liquid phase in terms of a network model perspective. We then present an unambiguous numerical identification and characterization of the universal topological properties of the phase, including ground state degeneracy, edge physics, and anyonic bulk excitations, by using a variety of powerful numerical probes, including the entanglement spectrum and modular transformations.
13/14 PSI - Condensed Matter Review - Lecture 13

Alioscia Hamma University of Naples Federico II

February 13, 2014

PIRSA:14020106
Applications of Information Theory in Direct Sum and Direct Product Problems

February 12, 2014

PIRSA:14020142

Quantum Information

A fundamental question in complexity theory is how much resource is needed to solve k independent instances of a problem compared to the resource required to solve one instance. Suppose solving one instance of a problem with probability of correctness p, we require c units of some resource in a given model of computation. A direct sum theorem states that in order to compute k independent instances of a problem, it requires k times units of the resource needed to compute one instance. A strong direct product theorem states that, with o(k • c) units of the resource, one can only compute all the k instances correctly with probability exponentially small in k. In this talk, I am going to present some of recent progress on direct sum and direct product theorems in the model of communication complexity and two-prover one-round games with information-theoretic approach. The talk is based on parts of my doctoral work.

Title	Date	Collection	Type	Info
Probabilistic protocols in quantum information	2014‑02‑13	Perimeter Institute Quantum Discussions	Scientific Series	View details
Firewall evasion by quantum gravity	2014‑02‑13	Quantum Gravity	Scientific Series	View details
Are non-Fermi-liquids stable to pairing?	2014‑02‑13	Emergence in Complex Systems	Conference	View details
On null singularities in general relativity	2014‑02‑13	Strong Gravity	Scientific Series	View details
Gauging symmetry of 2D topological phases	2014‑02‑13	Emergence in Complex Systems	Conference	View details
13/14 PSI - Cosmology Review - Lecture 12	2014‑02‑13	13/14 PSI - Cosmology Review	Course	View details
Incoherent metals	2014‑02‑13	Emergence in Complex Systems	Conference	View details
13/14 PSI - String Theory Review - Lecture 13	2014‑02‑13	13/14 PSI - String Theory Review	Course	View details
Interacting electronic topological insulators in three dimensions	2014‑02‑13	Emergence in Complex Systems	Conference	View details
Chiral spin liquid and emergent anyons in a Kagome lattice Mott insulator	2014‑02‑13	Emergence in Complex Systems	Conference	View details
13/14 PSI - Condensed Matter Review - Lecture 13	2014‑02‑13	13/14 PSI - Condensed Matter Review	Course	View details
Applications of Information Theory in Direct Sum and Direct Product Problems	2014‑02‑12	Perimeter Institute Quantum Discussions	Scientific Series	View details

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