Decoherence in the Pure Dephasing Spin-Boson Model with Hermitian or Non-Hermitian Bath

TL;DR

This paper analytically studies qubit decoherence in a pure dephasing spin-boson model with Hermitian and non-Hermitian baths, revealing how non-Hermitian baths can suppress decoherence and highlighting singular behaviors at specific parameter values.

Contribution

It provides the first analytical comparison of equilibrium and non-equilibrium correlation functions in this model and demonstrates decoherence suppression by non-Hermitian baths.

Findings

Non-Hermitian baths suppress qubit decoherence across all parameters.

Singular dependence of correlation functions at integer values of bath parameters.

Analytical establishment of the similarity between $P_x(t)$ and $C_x(t)$.

Abstract

In this paper, we investigate the decoherence of qubit due to its coupling to a Hermitian or a non-Hermitian bath within the pure dephasing spin-boson model. First, using this model, we analytically establish the previously anticipated similarity between the non-equilibrium and the equilibrium correlation functions $P_x(t)$ and $C_x(t)$. Then, in the short/long time asymptotic behaviors of $P_x(t)$, we find singular dependence on $A$ (coupling strength) and $s$ (bath exponent) at their integer values. Finally, we find that the non-Hermitian bath tends to suppress the decoherence of qubit for all values of $A$ and $s$, in contrast to the conclusion of Dey et al. . Our results show the potential of non-Hermitian environment engineering in suppressing the decoherence of qubit.