Dynamical decoupling efficiency versus quantum non-Markovianity

TL;DR

This paper explores how non-Markovian environments affect the efficiency of dynamical decoupling in preserving qubit coherence, finding that non-Markovianity can hinder decoherence suppression.

Contribution

It demonstrates that engineering non-Markovian environments can be detrimental to dynamical decoupling effectiveness and identifies optimal parameters for maximum coherence.

Findings

Non-Markovian environments reduce dynamical decoupling efficiency.

Each pulse reverses quantum information flow.

Optimal reservoir parameters enhance stationary coherence.

Abstract

We investigate the relationship between non-Markovianity and the effectiveness of a dynamical decoupling protocol for qubits undergoing pure dephasing. We consider an exact model in which dephasing arises due to a bosonic environment with a spectral density of the Ohmic class. This is parametrised by an Ohmicity parameter by changing which we can model both Markovian and non-Markovian environments. Interestingly, we find that engineering a non-Markovian environment is detrimental to the efficiency of the dynamical decoupling scheme, leading to a worse coherence preservation. We show that each dynamical decoupling pulse reverses the flow of quantum information and, on this basis, we investigate the connection between dynamical decoupling efficiency and the reservoir spectral density. Finally, in the spirit of reservoir engineering, we investigate the optimum system-reservoir parameters for achieving maximum stationary coherences.