Decoherence-free evolution of time-dependent superposition states of two-level systems and thermal effects

TL;DR

This paper explores methods to engineer reservoirs for two-level quantum systems to maintain superposition states free from decoherence, including effects of thermal environments, through analytical and numerical approaches.

Contribution

It introduces a time-dependent master equation approach for reservoir engineering and provides a general recipe for nonadiabatic coherent evolution of fermionic systems.

Findings

Reservoir engineering can preserve superposition states at zero temperature.

Thermal effects reduce the fidelity of protected superpositions.

Analytical results are validated by numerical simulations.

Abstract

In this paper we detail some results advanced in a recent letter [Prado et al., Phys. Rev. Lett. 102 073008 (2009)] showing how to engineer reservoirs for two-level systems at absolute zero by means of a time-dependent master equation leading to a nonstationary superposition equilibrium state. We also present a general recipe showing how to build nonadiabatic coherent evolutions of a fermionic system interacting with a bosonic mode and investigate the influence of thermal reservoirs at finite temperature on the fidelity of the protected superposition state. Our analytical results are supported by numerical analysis of the full Hamiltonian model.