Improving the precision of frequency estimation via long-time coherences

TL;DR

This paper introduces a novel quantum frequency estimation method leveraging long-time coherence in individual sensors, surpassing entanglement-based strategies for finite probes through environmental engineering.

Contribution

It proposes a new approach that exploits long-time quantum coherence and environmental control, outperforming traditional entanglement-based methods in finite-sample scenarios.

Findings

Long-time coherence enhances frequency estimation precision.

Environmental engineering enables surpassing entanglement-based limits.

The scheme is feasible with trapped ion quantum sensors.

Abstract

In the last years several estimation strategies have been formulated to determine the value of an unknown parameter in the most precise way, taking into account the presence of noise. These strategies typically rely on the use of quantum entanglement between the sensing probes and they have been shown to be optimal in the asymptotic limit in the number of probes, as long as one performs measurements on shorter and shorter time scales. Here, we present a different approach to frequency estimation, which exploits quantum coherence in the state of each sensing particle in the long time limit and is obtained by properly engineering the environment. By means of a commonly used master equation, we show that our strategy can overcome the precision achievable with entanglement-based strategies for a finite number of probes. We discuss a possible implementation of the scheme in a realistic setup that uses trapped ions as quantum sensors.