Quantum sensing enhanced by adaptive periodic quantum control

TL;DR

This paper introduces an adaptive quantum control method that significantly enhances the precision of quantum sensing by a single probe, especially for weakly coupled quantum systems, achieving a super-classical scaling.

Contribution

The authors propose a novel adaptive periodic quantum control strategy that improves sensing precision from 1/T to 1/T^2 scaling without direct access to the target.

Findings

Precision improves from 1/T to 1/T^2 scaling.

Enhancement increases as probe-target coupling decreases.

Method enables ultrasensitive sensing of weakly coupled quantum objects.

Abstract

Using a single quantum probe to sense other quantum objects offers distinct advantages but suffers from some limitations that may degrade the sensing precision severely, especially when the probe-target coupling is weak. Here we propose a strategy to improve the sensing precision by using the quantum probe to engineer the evolution of the target. We consider an exactly solvable model, in which a qubit is used as the probe to sense the frequency of a harmonic oscillator. We show that by applying adaptive periodic quantum control on the qubit, the sensing precision can be enhanced from 1/T scaling with the total time cost T to 1/T^{2} scaling, thus improving the precision by several orders of magnitudes. Such improvement can be achieved without any direct access to the oscillator and the improvement increases with decreasing probe-target coupling. This provides a useful routine to ultrasensitive quantum sensing of weakly coupled quantum objects.