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arXiv · quant-ph/0612008

Mixed-state fidelity and quantum criticality at finite temperature

Paolo Zanardi·H. T. Quan·Xiaoguang Wang·C. P. Sun
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Abstract

We extend to finite temperature the fidelity approach to quantum phase transitions (QPTs). This is done by resorting to the notion of mixed-state fidelity that allows one to compare two density matrices corresponding to two different thermal states. By exploiting the same concept we also propose a finite-temperature generalization of the Loschmidt echo. Explicit analytical expressions of these quantities are given for a class of quasi-free fermionic Hamiltonians. A numerical analysis is performed as well showing that the associated QPTs show their signatures in a finite range of temperatures.

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Paolo Zanardi, H. T. Quan, Xiaoguang Wang, C. P. Sun. 2006-12-01. Mixed-state fidelity and quantum criticality at finite temperature. https://doi.org/10.1103/physreva.75.032109

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