Ultrasensitive transverse deflection measurement with two-photon interference
Phys. Rev. Applied 25, 014009 – Published 6 January, 2026
DOI: https://doi.org/10.1103/s7yr-2fk3
Abstract
Hong-Ou-Mandel (HOM) interference is an intrinsic quantum phenomenon that goes beyond the possibilities of classical physics, and enables various applications in quantum metrology. While the timing resolution of HOM-based sensors is generally investigated, the ultimate quantum sensitivity in the estimation of transverse deflection or displacement between paired photons interfering at a balanced beam splitter has been explored relatively little. Here we present an experimental demonstration of a spatial HOM interferometry for measuring the transverse deflection of an optical beam by using transverse momentum sampling measurements. This feasible scheme suffices to achieve great precision with comparatively little technological effort, which circumvents the stringent requirement in direct imaging resolution at the diffraction limit. We can adaptively determine optimum working points using a Fisher information analysis, and demonstrate an optimized spatial HOM interferometry according to practical applications. These results may significantly facilitate the use of quantum interference for high-precision spatial sensing, and may pave the way to more complex quantum imaging techniques such as nanoscopic microscopy.
