Improving the Precision of Optical Metrology by Detecting Fewer Photons

TL;DR

This paper introduces a biased weak measurement protocol that enhances optical metrology precision by detecting fewer photons, effectively overcoming detector saturation limitations and achieving significantly improved measurement accuracy.

Contribution

The authors develop a biased weak measurement technique that maintains high Fisher information with fewer photons, improving optical measurement precision under practical detector constraints.

Findings

Achieved nearly tenfold improvement in magnetic-sensing precision.

Demonstrated effectiveness of biased weak measurement in overcoming detector saturation.

Applicable to various optical measurement schemes with low-cost setups.

Abstract

In optical metrological protocols to measure physical quantities, it is, in principle, always beneficial to increase photon number to improve measurement precision. However, practical constraints prevent arbitrary increase of n due to the imperfections of a practical detector, especially when the detector response is dominated by saturation effect. In this work, we show that a modified weak measurement protocol, namely, biased weak measurement significantly improves the precision of optical metrology in the presence of saturation effect. This method detects an ultra-small fraction of photons while maintains considerable amount of metrological information. The biased pre-coupling leads to an additional reduction of photons in the post-selection and generates an extinction point in the spectrum distribution, which is extremely sensitive to the estimated parameter and difficult to be saturated. Therefore, the Fisher information can be persistently enhanced by increasing the photon number. In our magnetic-sensing experiment, biased weak measurement achieves precision approximately one order of magnitude better than those of previously used methods. The proposed method can be applied in various optical measurement schemes to circumvent detector saturation effect with low-cost apparatuses.