Experimental feedback control of quantum systems using weak measurements

TL;DR

This paper demonstrates experimentally that weak measurements enhance feedback control of qubits, allowing better stabilization against noise than traditional methods, thus advancing quantum control techniques.

Contribution

It provides the first experimental evidence that weak measurements can improve quantum feedback control beyond conventional measurement strategies.

Findings

Weak measurements improve qubit stabilization in practice.

Feedback control with weak measurements outperforms traditional methods.

Weak measurements are feasible despite implementation challenges.

Abstract

A goal of the emerging field of quantum control is to develop methods for quantum technologies to function robustly in the presence of noise. Central issues are the fundamental limitations on the available information about quantum systems and the disturbance they suffer in the process of measurement. In the context of a simple quantum control scenario--the stabilization of non-orthogonal states of a qubit against dephasing--we experimentally explore the use of weak measurements in feedback control. We find that, despite the intrinsic difficultly of implementing them, weak measurements allow us to control the qubit better in practice than is even theoretically possible without them. Our work shows that these more general quantum measurements can play an important role for feedback control of quantum systems.