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Introduction to Effective Field Theories - Lecture 12

Cliff Burgess McMaster University

February 14, 2014

PIRSA:14020093
Many-body localization with dipoles

Chris Laumann Boston University

February 14, 2014

PIRSA:14020129
13/14 PSI - Cosmology Review - Lecture 13

Latham Boyle University of Edinburgh

February 14, 2014

PIRSA:14020102
Low Spin State Mott Insulators and Emergence of novel Quantum Spin Liquids

Baskaran Ganapathy Institute of Mathematical Sciences

February 14, 2014

PIRSA:14020128
13/14 PSI - String Theory Review - Lecture 14

Davide Gaiotto Perimeter Institute for Theoretical Physics

February 14, 2014

PIRSA:14020034
A unification of symmetric Z2 spin liquids on kagome lattice

Yuan-Ming Lu

February 14, 2014

PIRSA:14020118
Introduction to Effective Field Theories - Lecture 11

Cliff Burgess McMaster University

February 14, 2014

PIRSA:14020089
How universal is the entanglement spectrum?

Anushya Chandran Perimeter Institute for Theoretical Physics

February 14, 2014

PIRSA:14020132
13/14 PSI - Condensed Matter Review - Lecture 14

Alioscia Hamma University of Naples Federico II

February 14, 2014

PIRSA:14020107
Introduction to Quantum Field Theory for Cosmology - Lecture 12

Achim Kempf University of Waterloo

February 13, 2014

PIRSA:14020005
Introduction to Quantum Field Theory for Cosmology - Lecture 11

Achim Kempf University of Waterloo

February 13, 2014

PIRSA:14020001
Probabilistic protocols in quantum information

Joshua Combes University of Colorado Boulder
February 13, 2014

PIRSA:14020138
Quantum Information

Introduction to Effective Field Theories - Lecture 12

Cliff Burgess McMaster University

February 14, 2014

PIRSA:14020093
Many-body localization with dipoles

Chris Laumann Boston University

February 14, 2014

PIRSA:14020129

Statistical mechanics is the framework that connects thermodynamics to the microscopic world. It hinges on the assumption of equilibration; when equilibration fails, so does much of our understanding. In isolated quantum systems, this breakdown is captured by the phenomenon known as many-body localization. This breakdown manifests in a variety of ways, as elucidated by much recent theoretical and numerical work. Many-body localized phases violate Ohm's law and Fourier's law as they conduct neither charge nor heat; they can exhibit symmetry breaking and/or topological orders in dimensions normally forbidden by Mermin-Wagner arguments; they hold potential as strongly interacting quantum computers due to the slow decay of local coherence.
In this talk, I will briefly introduce the basic phenomena of many-body localization and review its theoretical status. To date, none of these phenomena has been observed in an experimental system, in part because of the isolation required to avoid thermalization. I will consider several dipolar systems which we believe to be ideal platforms for the realization of MBL phases and for investigating the associated delocalization phase transition. The presence of strong interactions in these systems underlies their potential for exploring physics beyond that of single particle Anderson localization. However, the power law of the dipolar interaction immediately raises the question: can localization in real space persist in the presence of such long-range interactions?
I will review and extend several arguments producing criteria for localization in the presence of power laws and present small-scale numerics regarding the MBL transition in several of the proposed dipolar systems.
Associated preprint:
N. Yao, CRL, S. Gopalakrishnan, M. Knap, M. Mueller, E. Demler., M. Lukin arXiv:1311.7151
13/14 PSI - Cosmology Review - Lecture 13

Latham Boyle University of Edinburgh

February 14, 2014

PIRSA:14020102
Low Spin State Mott Insulators and Emergence of novel Quantum Spin Liquids

Baskaran Ganapathy Institute of Mathematical Sciences

February 14, 2014

PIRSA:14020128

In a conventional Mott insulator, magnitude of local spin moments remain fixed. They are `fixed spin Mott insulators'. We suggest that, in a multi orbital Hubbard model, when local Hund coupling is won over by inter-orbital superexchange couplings between neighboring sites, local spin moment can decrease its value in a cooperative fashion, through a first order phase transition, These are `Low spin state Mott insulators' (LSSMI). The minimal value of spins that can be reached are zero (half), for even (odd) number of electrons per site, We show that in LSSMI, depending on orbital degeneracy and electron number per site, novel quantum spin liquids can emerge, We discuss systems such as Fe arsenide, Fe selenide family and La2CoO3 in the light of our proposal. Certain long standing puzzles, including absence of any magnetic phase transition in La2CoO3 is explained in terms of a novel quantum spin liquid. Some properties of this spin liquid, a liquid of `quantum strings' will be discussed and some predictions made.
13/14 PSI - String Theory Review - Lecture 14

Davide Gaiotto Perimeter Institute for Theoretical Physics

February 14, 2014

PIRSA:14020034
A unification of symmetric Z2 spin liquids on kagome lattice

Yuan-Ming Lu

February 14, 2014

PIRSA:14020118

While there is mounting numerical evidence for a gapped Z2 spin liquid in the kagome Heisenberg model, a complete characterization of this topological phase remains to be accomplished. A defining property, the projective symmetry group (PSG) which fixes how the emergent excitations of the spin liquid phase transform under symmetry, remains to be determined. Following a Chern-Simons field theory, we show how PSG determines measurable properties of a Z2 spin liquid, such as the existence of symmetry protected gapless edge states. This fact enables us to unify two distinct types of projected wavefunctions for Z2 spin liquids: the Schwinger-boson states and the fermionic spinon states. We also provide concrete predictions for identifying the spin liquid ground state on the kagome lattice.
Introduction to Effective Field Theories - Lecture 11

Cliff Burgess McMaster University

February 14, 2014

PIRSA:14020089
How universal is the entanglement spectrum?

Anushya Chandran Perimeter Institute for Theoretical Physics

February 14, 2014

PIRSA:14020132

It is now commonly believed that the ground state entanglement spectrum (ES) exhibits universal features characteristic of a given phase. In this talk, I will present evidence to the contrary. I will show that the entanglement Hamiltonian can undergo quantum phase transitions in which its ground state and low energy spectrum exhibit singular changes, even when the physical system remains in the same phase. For broken symmetry problems, this implies that the ES and the Renyi entropies can mislead entirely, while for quantum Hall systems the ES has much less universal content than assumed to date. I will also discuss the consequences of the eigenstate thermalization hypothesis for the entanglement Hamiltonian, showing that a pure state in a sub-system can capture the properties of the reduced density matrix.
13/14 PSI - Condensed Matter Review - Lecture 14

Alioscia Hamma University of Naples Federico II

February 14, 2014

PIRSA:14020107
Introduction to Quantum Field Theory for Cosmology - Lecture 12

Achim Kempf University of Waterloo

February 13, 2014

PIRSA:14020005
Introduction to Quantum Field Theory for Cosmology - Lecture 11

Achim Kempf University of Waterloo

February 13, 2014

PIRSA:14020001
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.

Title	Date	Collection	Type	Info
Introduction to Effective Field Theories - Lecture 12	2014‑02‑14	Introduction to Effective Field Theories	Course	View details
Many-body localization with dipoles	2014‑02‑14	Emergence in Complex Systems	Conference	View details
13/14 PSI - Cosmology Review - Lecture 13	2014‑02‑14	13/14 PSI - Cosmology Review	Course	View details
Low Spin State Mott Insulators and Emergence of novel Quantum Spin Liquids	2014‑02‑14	Emergence in Complex Systems	Conference	View details
13/14 PSI - String Theory Review - Lecture 14	2014‑02‑14	13/14 PSI - String Theory Review	Course	View details
A unification of symmetric Z2 spin liquids on kagome lattice	2014‑02‑14	Emergence in Complex Systems	Conference	View details
Introduction to Effective Field Theories - Lecture 11	2014‑02‑14	Introduction to Effective Field Theories	Course	View details
How universal is the entanglement spectrum?	2014‑02‑14	Emergence in Complex Systems	Conference	View details
13/14 PSI - Condensed Matter Review - Lecture 14	2014‑02‑14	13/14 PSI - Condensed Matter Review	Course	View details
Introduction to Quantum Field Theory for Cosmology - Lecture 12	2014‑02‑13	Quantum Field Theory for Cosmology - 2014	Course	View details
Introduction to Quantum Field Theory for Cosmology - Lecture 11	2014‑02‑13	Quantum Field Theory for Cosmology - 2014	Course	View details
Probabilistic protocols in quantum information	2014‑02‑13	Perimeter Institute Quantum Discussions	Scientific Series	View details

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