[quantum-info] coming colloquium Monday Sept 24

[Debbie Leung]

Sept. 24, 2012 at 12:30 (** sharp **) p.m. RAC1 2009

Speaker: Daniel Nagaj

Title: Criticality without Frustration

Abstract

How much entanglement can there be in a ground state of a simple 1D system 
with local interactions? Critical behavior (e.g. long-range correlations) 
is usually associated with frustration. When a system is unfrustrated (all 
local Hamiltonian terms are minimized), we expect the ground state to be 
simple. While this holds for qubits, things are quite different for 
higher-spin particles (already for qutrits). We'll talk about a state made 
from well bracketed words and look at the proof of its high entanglement 
entropy scaling and a lower bound of the Hamiltonian using congestion in 
graphs, parenting trees, many uses of the projection lemma and other fun 
stuff.

joint work with Sergey Bravyi, Libor Caha, Ramis Movassagh and Peter Shor, 
http://lanl.arxiv.org/abs/1203.5801

keywords: unfrustrated ground states, quantum 2-SAT, qutrits, Motzkin 
paths, perturbation theory, projection lemma, fractional matchings