Narrowband Frequency-Entangled Photon Source for Hong-Ou-Mandel Interferometry

TL;DR

This paper presents a narrowband, resonant PDC-based frequency-entangled photon source that enhances HOM interferometry sensitivity and extends sensing range to meters, with high-contrast quantum beating at large frequency detuning.

Contribution

It introduces a novel resonant PDC source in a crystalline whispering gallery mode resonator for generating narrowband, highly nondegenerate frequency-entangled photons.

Findings

Achieved meter-scale sensing range with MHz bandwidth photons.

Observed high-contrast quantum beating with sub-picosecond resolution.

Demonstrated potential for quantum metrology and information processing.

Abstract

Hong-Ou-Mandel (HOM) interferometry with entangled photons exhibits distinctive quantum features. By introducing frequency entanglement (discrete-color entangled states) into HOM interference, the characteristic HOM dip is modulated by sinusoidal fringes, which significantly enhance the sensitivity of HOM sensors. The frequency-entangled photon sources demonstrated to date rely on non-resonant parametric down-conversion (PDC), which limits the photon coherence length and, consequently, restricts the sensing dynamic range to the sub-millimeter scale. In this work, we demonstrate narrowband frequency-entangled photon source based on resonant PDC in a crystalline whispering gallery mode resonator. The MHz-level spectral bandwidth of photons enables a meter-scale dynamic range. With highly nondegenerate frequency-entangled photon pairs featuring a 96 THz frequency detuning, we observe high-contrast quantum beating with sub-picosecond resolution in the HOM experiment. Our WGMR-based frequency-entangled photon source has potential applications in quantum metrology and quantum information processing.