Improved mirror position estimation using resonant quantum smoothing

TL;DR

This paper demonstrates that quantum smoothing can significantly improve the precision of mirror position estimation in resonant systems, surpassing previous limits and achieving over three times enhancement.

Contribution

It introduces a resonant quantum smoothing technique that outperforms non-resonant methods and achieves unprecedented precision in cavity mirror position estimation.

Findings

Quantum smoothing yields over three times improvement in resonant systems.

Resonant structures enhance the effectiveness of quantum smoothing.

Intra-cavity light provides finer measurement precision than free-space quantum resources.

Abstract

Quantum parameter estimation, the ability to precisely obtain a classical value in a quantum system, is very important to many key quantum technologies. Many of these technologies rely on an optical probe, either coherent or squeezed states to make a precise measurement of a parameter ultimately limited by quantum mechanics. We use this technique to theoretically model, simulate and validate by experiment the measurement and precise estimation of the position of a cavity mirror. In non-resonant systems, the achieved estimation enhancement from quantum smoothing over optimal filtering has not exceeded a factor two, even when squeezed state probes were used. Using a coherent state probe, we show that using quantum smoothing on a mechanically resonant structure driven by a resonant forcing function can result significantly greater improvement in parameter estimation than with non-resonant systems. In this work, we show that it is possible to achieve a smoothing improvement by a factor in excess of three times over optimal filtering. By using intra-cavity light as the probe we obtain finer precision than has been achieved with the equivalent quantum resources in free-space.