Phase transitions and metastability in the distribution of the bipartite entanglement of a large quantum system

A. De Pasquale, P. Facchi, G. Parisi, S. Pascazio, A. Scardicchio

Published 2009-11-19, updated 2010-01-13Version 2

We study the distribution of the Schmidt coefficients of the reduced density matrix of a quantum system in a pure state. By applying general methods of statistical mechanics, we introduce a fictitious temperature and a partition function and translate the problem in terms of the distribution of the eigenvalues of random matrices. We investigate the appearance of two phase transitions, one at a positive temperature, associated to very entangled states, and one at a negative temperature, signalling the appearance of a significant factorization in the many-body wave function. We also focus on the presence of metastable states (related to 2-D quantum gravity) and study the finite size corrections to the saddle point solution.