Robust Smoothing for Estimating Optical Phase Varying as a Continuous Resonant Process

TL;DR

This paper develops a robust smoothing technique for continuous optical phase estimation under uncertain resonant noise, improving worst-case performance over traditional methods.

Contribution

It introduces a robust fixed-interval smoother tailored for uncertain resonant noise processes in optical phase estimation, enhancing robustness and accuracy.

Findings

Robust smoother outperforms optimal smoother in worst-case scenarios.

Robust smoother surpasses robust filter in uncertain system performance.

Improved accuracy in homodyne phase estimation of light states.

Abstract

Continuous phase estimation is known to be superior in accuracy as compared to static estimation. The estimation process is, however, desired to be made robust to uncertainties in the underlying parameters. Here, homodyne phase estimation of coherent and squeezed states of light, evolving continuously under the influence of a second-order resonant noise process, are made robust to parameter uncertainties using a robust fixed-interval smoother, designed for uncertain systems satisfying a certain integral quadratic constraint. We observe that such a robust smoother provides improved worst-case performance over the optimal smoother and also performs better than a robust filter for the uncertain system.