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arXiv · 2506.03098

High-Precision Measurement of Time Delay with Frequency-Resolved Hong-Ou-Mandel Interference of Weak Coherent States

Francesco Di Lena·Fabrizio Sgobba·Danilo Triggiani·Andrea Andrisani·Cosmo Lupo·Piergiorgio Daniele·Gennaro Fratta·Giulia Acconcia·Ivan Rech·Luigi Santamaria Amato
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Abstract

We demonstrate a scheme for high-precision measurements of time delay based on frequency-resolved Hong-Ou-Mandel (HOM) interference. Our approach is applied to weak coherent states and exploits an array of single-photon avalanche diodes (SPADs). Unlike conventional HOM experiments, our setup enables high-precision measurements producing an uncertainty per coincidence of about $\sim 10$ ps even for photons separated by delays up to $\sim 4$ ps so much greater than their coherence time where ordinary non-resolved HOM fails. This result confirms our newly developed theoretical predictions that consider, differently from previous theoretical results, a finite frequency resolution in the detection. We compare the performance of this scheme against the conventional non-resolved case. Experimental data align well with the predictions of quantum estimation theory, demonstrating a significant reduction in the uncertainty. Due to the physics of the frequency-resolved HOM effect, the gain in precision is particularly high when the estimated time delay is much longer than the coherence time.

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Francesco Di Lena, Fabrizio Sgobba, Danilo Triggiani, Andrea Andrisani, Cosmo Lupo, Piergiorgio Daniele, Gennaro Fratta, Giulia Acconcia, Ivan Rech, Luigi Santamaria Amato. 2025-06-03. High-Precision Measurement of Time Delay with Frequency-Resolved Hong-Ou-Mandel Interference of Weak Coherent States. https://doi.org/10.1002/qute.202500636

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