Eternally non-Markovian dynamics of a qubit interacting with a single-photon wavepacket

TL;DR

This paper investigates the complex non-Markovian dynamics of a qubit interacting with a single-photon wavepacket, revealing conditions under which memory effects and information backflow occur or are suppressed.

Contribution

It introduces a hierarchy of master equations for phase covariant qubit evolution influenced by temporal correlations in the input field.

Findings

Memory effects depend on the singularity of the time-local generator.

In the resonant case, regular generators prevent information backflow.

Exponential profile analysis illustrates key features of qubit evolution.

Abstract

An evolution of a two-level system (qubit) interacting with a single-photon wave packet is analyzed. It is shown that a hierarchy of master equations gives rise to phase covariant qubit evolution. The temporal correlations in the input field induce nontrivial memory effects for the evolution of a qubit. It is shown that in the resonant case whenever time-local generator is regular (does not display singularities) the qubit evolution never displays information backflow. However, in general the generator might be highly singular leading to intricate non-Markovian effects. A detailed analysis of the exponential profile is provided which allows to illustrate all characteristic feature of the qubit evolution.