Entanglement free Metrology Exploiting Multimode Hong Ou Mandel Sensor Advantage

Abstract

The Hong-Ou-Mandel (HOM) interference in the multimode frequency domain has been widely used in precision metrology, benefiting from robustness against dispersion and phase noise, as well as a large dynamic range and compatibility with fragile samples. Conventional multimode HOM metrology exploits frequency-entangled states, which naturally satisfy bosonic exchange symmetry under any centered symmetric joint spectral distribution, to provide these advantages. However, these entangled states are typically generated via spontaneous parametric down-conversion (SPDC), requiring strong pump lasers that hinder practical implementation. In this paper, we employ frequency product states, which do not possess entanglement or path-mode exchange symmetry, as the probe state and post-select measurement outcomes exhibiting frequency anti-correlation. Our results demonstrate that these metrological advantages arise neither from entanglement nor from bosonic exchange symmetry, but rather from spectral anti-correlation