paper

Ground state fidelity and quantum phase transitions in free Fermi systems

arXiv:quant-ph/0606130 · doi:10.1088/1742-5468/2007/02/L02002

Abstract

We compute the fidelity between the ground states of general quadratic fermionic hamiltonians and analyze its connections with quantum phase transitions. Each of these systems is characterized by a real matrix whose polar decomposition, into a non-negative and a unitary , contains all the relevant ground state (GS) information. The boundaries between different regions in the GS phase diagram are given by the points of, possibly asymptotic, singularity of . This latter in turn implies a critical drop of the fidelity function. We present general results as well as their exemplification by a model of fermions on a totally connected graph.

4 pages, 2 figures

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