Squeezing-Enhanced Rotational Doppler Metrology

TL;DR

This paper presents a quantum-enhanced method using squeezed light to measure the rotation speed of a surface via the rotational Doppler effect, achieving Heisenberg scaling in ideal conditions and outperforming classical methods under noise.

Contribution

It introduces a continuous-variable quantum protocol utilizing squeezed and displaced Laguerre-Gaussian modes for rotational Doppler metrology, demonstrating quantum advantage and robustness against noise.

Findings

Achieves Heisenberg scaling in ideal noiseless conditions.

Quantum protocol outperforms classical strategies with optimized energy distribution.

Performance degrades with noise but remains advantageous through parameter optimization.

Abstract

A rotating surface can induce a frequency shift in incident light by changing its angular momentum, a phenomenon known as the rotational Doppler effect. This effect provides a means to estimate the angular velocity of the rotating surface. In this work, we develop a continuous-variable quantum protocol for estimating the angular velocity of a rotating surface via the rotational Doppler effect. Our approach exploits squeezed and displaced Laguerre-Gaussian modes as quantum resources, which interact with a rotating metallic disc with surface roughness. The frequency shift induced by the rotational Doppler effect is then measured using a homodyne detection scheme. By analyzing the Fisher information, we demonstrate that the proposed squeezing-enhanced protocol achieves Heisenberg scaling in the ideal noiseless regime. Furthermore, we investigate the influence of noise and consider different surface models to assess their impact on the protocol's performance. While Heisenberg scaling is degraded in the presence of noise, we show that optimizing the energy allocation ratio between displacement and squeezing of the probe ensures that the quantum strategy consistently outperforms its classical counterpart.