Quantum dynamical decoupling by shaking the close environment

TL;DR

This paper explores a novel approach to quantum decoupling by manipulating the environment instead of the target system, revealing counterintuitive strategies for reducing decoherence through environment control.

Contribution

It introduces and analyzes environment-side decoupling methods, including Hamiltonian stirring and increased decoherence, using advanced modeling techniques.

Findings

Isolating the environment from noise isn't always optimal.

Environment stirring can effectively decouple the environment from the target.

Counterintuitively, increasing environmental decoherence can sometimes protect the target.

Abstract

Quantum dynamical decoupling is a procedure to cancel the effective coupling between two systems by applying sequences of fast actuations, under which the coupling Hamiltonian averages out to leading order(s). One of its prominent uses is to drive a target system in such a way as to decouple it from a less protected one. The present manuscript investigates the dual strategy: acting on a noisy "environment" subsystem such as to decouple it from a target system. The potential advantages are that actions on the environment commute with system operations, and that imprecisions in the decoupling actuation are harmless to the target. We consider two versions of environment-side decoupling: adding an imprecise Hamiltonian drive which stirs the environment components; and, increasing the decoherence rates on the environment. The latter can be viewed as driving the environment with pure noise and our conclusions establish how, maybe counterintuitively, isolating the environment from noise sources as much as possible is often not the best option. We explicitly analyze the induced decoherence on the target system and establish how it is influenced by the parameters in both cases. The analysis combines Lindbladian derivation, adiabatic elimination, and Floquet modeling in a way that may be of independent interest.