Near-video frame rate quantum sensing using Hong-Ou-Mandel interferometry

Hong-Ou-Mandel (HOM) interference, bunching of two indistinguishable photons on a balanced beam-splitter, has emerged as a promising tool for quantum sensing. There is a need for wide spectral-bandwidth photon pairs (for high-resolution sensing) with high brightness (for fast sensing). Here we show the generation of photon-pairs with flexible spectral bandwidth even using single-frequency, continuous-wave diode laser enabling high-precision, real-time sensing. Using 1-mm-long periodically-poled KTP crystal, we produced degenerate photon-pairs with a spectral bandwidth of 163.42±1.68 nm resulting in a HOM-dip width of 4.01±0.04 μm to measure a displacement of 60 nm, and sufficiently high brightness to enable the measurement of vibrations with an amplitude of 205 ± 0.75 nm and frequency of 8 Hz. Fisher-information and maximum likelihood estimation enables optical delay measurements as small as 4.97 nm with precision (Cramér-Rao bound) and accuracy of 0.89 and 0.54 nm, respectively, therefore showing HOM sensing capability for real-time, precision-augmented, in-field quantum sensing applications