Active Quantum Reservoir Engineering: Using a Qubit to Manipulate its Environment

TL;DR

This paper introduces a theoretical framework for active quantum reservoir engineering, where a qubit's time-dependent control manipulates its environment, enabling new functionalities in open quantum systems.

Contribution

It develops a novel framework for actively controlling the environment of a quantum system using a qubit, expanding beyond traditional passive reservoir engineering methods.

Findings

Qualitative agreement with previous experiments

Finite-size effects enable environment manipulation

Active control unlocks new functionalities

Abstract

Quantum reservoir engineering leverages dissipative processes to achieve desired behavior, with applications ranging from entanglement generation to quantum error correction. Therein, a structured environment acts as an entropy sink for the system and no time-dependent control over the system is required. We develop a theoretical framework for active reservoir engineering, where time-dependent control over a quantum system is used to manipulate its environment. In this case, the system may act as an entropy sink for the environment. Our framwork captures the dynamical interplay between system and environment, and provides an intuitive picture of how finite-size effects and system-environment correlations allow for manipulating the environment by repeated initialization of the quantum system. We illustrate our results with two examples: a superconducting qubit coupled to an environment of two-level systems and a semiconducting quantum dot coupled to nuclear spins. In both scenarios, we find qualitative agreement with previous experimental results, illustrating how active control can unlock new functionalities in open quantum systems.