Decoherence and the Loschmidt echo.

  title={Decoherence and the Loschmidt echo.},
  author={Fernando M. Cucchietti and Diego A. R. Dalvit and Juan Pablo Paz and Wojciech H. Zurek},
  journal={Physical review letters},
  volume={91 21},
Decoherence causes entropy increase that can be quantified using, e.g., the purity sigma=Trrho(2). When the Hamiltonian of a quantum system is perturbed, its sensitivity to such perturbation can be measured by the Loschmidt echo M(t). It is given by the squared overlap between the perturbed and unperturbed state. We describe the relation between the temporal behavior of sigma(t) and the average Mmacr;(t). In this way we show that the decay of the Loschmidt echo can be analyzed using tools… CONTINUE READING