<!doctype html public "-//W3C//DTD W3 HTML//EN">
<html><head><style type="text/css"><!--
blockquote, dl, ul, ol, li { padding-top: 0 ; padding-bottom: 0 }
--></style><title>MIT Quantum Information Processing Seminar
Announcemen</title></head><body>
<div>There will be no QIP seminar on Monday April 12, due to a
cancellation.</div>
<div><br></div>
<div>The following week's MIT QIP seminar will take place on Monday,
April 19 at 16:00 in 4-237, and features:</div>
<div><br></div>
<hr>
<div align="center"><font size="+2"><b>Entanglement Beyond
Subsystems</b></font></div>
<div align="center"><br></div>
<div align="center"><font size="+1"><i>by</i> Lorenza Viola (<i>J. R.
Oppenheimer Fellow, CCS-3, Los Alamos National Lab</i>)</font></div>
<div align="center"><br></div>
<div align="center"><u>ABSTRACT</u></div>
<div><br></div>
<blockquote>Characterizing and quantifying quantum correlations in
complex systems is critical for quantum information science as well as
for a variety of physical phenomena, including phase transitions in
matter. In this talk, I will discuss a generalization of
entanglement based on the idea that entanglement is relative to a
distinguished subspace of physical observables rather than a
distinguished subsystem decomposition. For multi-qubit systems,
conventional entanglement is recovered in the special case where the
set of all local observables on individual subsystems is preferred. By
going beyond the standard distinguishable-subsystem framework,
however, generalized entanglement naturally lends itself to
applications in the condensed-matter setting. In particular, by
focusing on the illustrative case of a one-dimensional spin-1/2 XY
model in a transverse field, I will show how generalized entanglement
provides useful diagnostic tools for identifying broken-symmetry
quantum phase transitions.</blockquote>
<div><br></div>
<blockquote><u>References</u>:</blockquote>
<blockquote>- "A subsystem-independent generalization of
entanglement," H. Barnum, E. Knill, G. Ortiz, R. Somma, and L.
Viola,<i> Phys. Rev. Lett.</i><b> 92</b>, 107902 (2004).</blockquote>
<blockquote>- "Nature and measure of entanglement in quantum
phase transitions," R. Somma, G. Ortiz, H. Barnum, E. Knill, and
L. Viola,<b> quant-ph/0403035</b>.</blockquote>
</body>
</html>