Pointer States via Engineered Dissipation

TL;DR

This paper demonstrates how to engineer pointer states in open quantum systems using tailored control protocols, ensuring long-lasting high-fidelity states despite environmental interactions, with applications validated through simulations.

Contribution

It introduces a method to create and stabilize pointer states via engineered dissipation and control, providing explicit pulse sequences and robustness analysis.

Findings

Engineered pointer states can be made to survive long times with high fidelity.

Control protocols are robust against systematic pulse errors.

Unintended pointer states can arise in dynamical decoupling due to control imperfections.

Abstract

Pointer states are long-lasting high-fidelity states in open quantum systems. We show how any pure state in a non-Markovian open quantum system can be made to behave as a pointer state by suitably engineering the coupling to the environment via open-loop periodic control. Engineered pointer states are constructed as approximate fixed points of the controlled open-system dynamics, in such a way that they are guaranteed to survive over a long time with a fidelity determined by the relative precision with which the dynamics is engineered. We provide quantitative minimum-fidelity bounds by identifying symmetry and ergodicity conditions that the decoherence-inducing perturbation must obey in the presence of control, and develop explicit pulse sequences for engineering any desired set of orthogonal states as pointer states. These general control protocols are validated through exact numerical simulations as well as semi-classical approximations in realistic single and two qubit dissipative systems. We also examine the role of control imperfections, and show that while pointer-state engineering protocols are highly robust in the presence of systematic pulse errors, the latter can also lead to unintended pointer-state generation in dynamical decoupling implementations, explaining the initial-state selectivity observed in recent experiments.