Quantum dynamical decoupling by shaking the close environment

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 target system only has a Hamiltonian coupling to this close environment which itself undergoes Lindbladian decoherence. 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. In this setting, we can explicitly analyze the induced decoherence on the target system, and focusing on the example of a two-level environment subsystem, we establish how the induced decoherence 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. (c) 2022 The Franklin Institute. Published by Elsevier Ltd. All rights reserved.