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arXiv · 2104.09235

Witnesses of coherence and dimension from multiphoton indistinguishability tests

Taira Giordani·Chiara Esposito·Francesco Hoch·Gonzalo Carvacho·Daniel J. Brod·Ernesto F. Galvão·Nicolò Spagnolo·Fabio Sciarrino
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Abstract

Quantum coherence marks a deviation from classical physics, and has been studied as a resource for metrology and quantum computation. Finding reliable and effective methods for assessing its presence is then highly desirable. Coherence witnesses rely on measuring observables whose outcomes can guarantee that a state is not diagonal in a known reference basis. Here we experimentally measure a novel type of coherence witness that uses pairwise state comparisons to identify superpositions in a basis-independent way. Our experiment uses a single interferometric set-up to simultaneously measure the three pairwise overlaps among three single-photon states via Hong-Ou-Mandel tests. Besides coherence witnesses, we show the measurements also serve as a Hilbert-space dimension witness. Our results attest to the effectiveness of pooling many two-state comparison tests to ascertain various relational properties of a set of quantum states.

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Taira Giordani, Chiara Esposito, Francesco Hoch, Gonzalo Carvacho, Daniel J. Brod, Ernesto F. Galvão, Nicolò Spagnolo, Fabio Sciarrino. 2021-04-19. Witnesses of coherence and dimension from multiphoton indistinguishability tests. https://doi.org/10.1103/physrevresearch.3.023031

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