Abstract
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 coupled to it. To characterize this transition quantitatively, we carefully examine the behavior of the Loschmidt echo (LE) of 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 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 vanish sharply.
- Received 11 October 2005
DOI:https://doi.org/10.1103/PhysRevLett.96.140604
©2006 American Physical Society