Two-photon phase-sensing with single-photon detection

• Published in: arXiv.org
• Main Authors: Vergyris, Panagiotis, Babin, Charles, Nold, Raphael, Gouzien, Elie, Herrmann, Harald, Silberhorn, Christine, Alibart, Olivier, Tanzilli, Sébastien, Kaiser, Florian
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 06.07.2020
• Subjects: Detection; Interference fringes; Photodiodes; Photon beams; Photons; Physics - Quantum Physics
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2007.02586

Path-entangled multi-photon states allow optical phase-sensing beyond the shot-noise limit, provided that an efficient parity measurement can be implemented. Realising this experimentally is technologically demanding, as it requires coincident single-photon detection proportional to the number of photons involved, which represents a severe challenge for achieving a practical quantum advantage over classical methods. Here, we exploit advanced quantum state engineering based on superposing two photon-pair creation events to realise a new approach that bypasses this issue. In particular, optical phase shifts are probed with a two-photon quantum state whose information is subsequently effectively transferred to a single-photon state. Notably, without any multiphoton detection, we infer phase shifts by measuring the average intensity of the single-photon beam on a photodiode, in analogy to standard classical measurements. Importantly, our approach maintains the quantum advantage: twice as many interference fringes are observed for the same phase shift, corresponding to N=2 path-entangled photons. Our results demonstrate that the advantages of quantum-enhanced phase-sensing can be fully exploited in standard intensity measurements, paving the way towards resource-efficient and practical quantum optical metrology.