Sequences of information backflow in local dephasing channels with spectral gaps

摘要

The flow of quantum information in local dephasing channels is analyzed over short and long times in case the structured reservoir of frequency modes exhibits a spectral gap in the density of modes over low frequencies. The presence of the low-frequency gap with upper cut-off frequency omega(g) produces an infinite sequence of long-time intervals over which information backflow appears. Though generally irregular, the time intervals exhibit, under certain conditions, upper bounds: the nth episode of information backflow has already started at the instant pi(2n-1)/omega(g), and already ended at the instant 2 pi n/omega(g), for every n = 1, 2, .... The intervals become regular over long times, tend to the asymptotic length pi/omega(g), as the supremum value, and are described analytically in terms of the structure of the spectral density near the upper cut-off frequency of the spectral gap. Consequently, engineering structured reservoirs of frequency modes with a spectral gap over low frequencies produces in local dephasing channels regular sequences of information backflow and recoherence over long times, along with non-Markovian evolution.