Measurement-based direct quantum feedback control in an open quantum system

TL;DR

This paper develops a measurement-based feedback control method for open quantum systems, enabling state stabilization and protection against noise through tailored feedback schemes.

Contribution

It derives a Lindblad-form master equation for quantum systems under measurement-based feedback and demonstrates effective state control and noise protection strategies.

Findings

MDFC can drive any initial state to a desired pure target state.

Weak measurement MDFC stabilizes nonorthogonal states against dephasing.

MDFC schemes protect certain mixed states composed of nonorthogonal states.

Abstract

We consider a general quantum system interacting with a bath and derive a master equation in the Lindblad form describing the evolution of the whole quantum system subjected to a measurement-based direct quantum feedback control (MDFC). As an example, we consider a qubit coupled with a dephasing environment under the MDFC. We show that for any given pure target state we can always find the corresponding MDFC scheme which can effectively drive any initial state into this target state. And by using appropriate MDFC scheme with weak measurement we can stabilize a single qubit initially prepared in one of two nonorthogonal states against dephasing noise. Furthermore, we can effectively protect a kind of known mixed states composed of two nonorthogonal states by using the corresponding MDFC scheme.