Decay of Loschmidt Echo Enhanced by Quantum Criticality

作者：H. T. Quan, Z. Song, Xingfang Liu, Paolo Zanardi, C. P. Sun · 发表于：Physical Review Letters · 年份：2006 · DOI：10.1103/physrevlett.96.140604 · 被引用次数：679 · 研究领域：Quantum many-body systems、Quantum Information and Cryptography、Quantum Computing Algorithms and Architecture

We study the transition of a quantum system from a pure state to a mixed one, which is induced by the quantum criticality of the surrounding system E coupled to it. To characterize this transition quantitatively, we carefully examine the behavior of the Loschmidt echo (LE) of E modeled as an Ising model in a transverse field, which behaves as a measuring apparatus in quantum measurement. It is found that the quantum critical behavior of E strongly affects its capability of enhancing the decay of LE: near the critical value of the transverse field entailing the happening of quantum phase transition, the off-diagonal elements of the reduced density matrix describing S vanish sharply.