Adaptive Homodyne Measurement of Optical Phase

TLDR

We experimentally demonstrate the power of feedback in quantum metrology, confirming that an adaptive homodyne technique can achieve superior single‑shot optical phase measurement. The method employs adaptive homodyne detection with real‑time feedback to estimate the phase of a light field. For weak coherent states with no prior phase knowledge, the adaptive homodyne estimator approaches the intrinsic quantum limit, outperforming previous techniques and underscoring the importance of real‑time feedback for reaching quantum limits in measurement and control. Citation: Phys.

Abstract

We present an experimental demonstration of the power of feedbackin quantum metrology, confirming the predicted [H. M. Wiseman, Phys. Rev. Lett. 75, 4587 (1995)] superior performanceof an adaptive homodyne technique for single-shotmeasurement of optical phase. For measurements performed on weak coherentstates with no prior knowledge of the signal phase, adaptive homodyneestimation approaches closer to the intrinsic quantum uncertaintythan any previous technique. Our results underscore the importanceof real-time feedback for reaching quantum limits in measurement andcontrol.