paper

Dynamics of decoherence: universal scaling of the decoherence factor

arXiv:1509.04649 · doi:10.1103/PhysRevA.93.012112

Abstract

We study the time dependence of the decoherence factor (DF) of a qubit globally coupled to an environmental spin system (ESS) which is driven across the quantum critical point (QCP) by varying a parameter of its Hamiltonian in time as or , to which the qubit is coupled starting at the time ; here, denotes the inverse quenching rate. In the limit of weak coupling, we analyze the time evolution of the DF in the vicinity of the QCP (chosen to be at ) and define three quantities, namely, the generalized fidelity susceptibility (defined right at the QCP), and the decay constants and which dictate the decay of the DF at a small but finite (). Using a dimensional analysis argument based on the Kibble-Zurek healing length, we show that as well as and indeed satisfy universal power-law scaling relations with and the exponents are solely determined by the spatial dimensionality of the ESS and the exponents associated with its QCP. Remarkably, using the numerical t-DMRG method, these scaling relations are shown to be valid in both the situations when the ESS is integrable and non-integrable and also for both linear and non-linear variation of the parameter. Furthermore, when an integrable ESS is quenched far away from the QCP, there is a predominant Gaussian decay of the DF with a decay constant which also satisfies a universal scaling relation.

4 pages, 4 figures, 6 pages supplementary material

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