PT-symmetric slowing down of decoherence

Abstract

We investigate $\mathcal{P}\mathcal{T}$-symmetric quantum systems ultraweakly coupled to an environment. We find that such open systems evolve under $\mathcal{P}\mathcal{T}$-symmetric, purely dephasing and unital dynamics. The dynamical map describing the evolution is then determined explicitly using a quantum canonical transformation. Furthermore, we provide an explanation of why $\mathcal{P}\mathcal{T}$-symmetric dephasing-type interactions lead to a critical slowing down of decoherence. This effect is further exemplified with an experimentally relevant system, a $\mathcal{P}\mathcal{T}$-symmetric qubit easily realizable, e.g., in optical or microcavity experiments.