Experimental quantification of four-photon indistinguishability

Photon indistinguishability plays a fundamental role in information processing, with applications such as linear-optical quantum computation and metrology. It is then necessary to develop appropriate tools to quantify the amount of this resource in a multiparticle scenario. Here we report a four-photon experiment in a linear-optical interferometer designed to simultaneously estimate the degree of indistinguishability between three pairs of photons. The interferometer design dispenses with the need of heralding for parametric down-conversion sources, resulting in an efficient and reliable optical scheme. We then use a recently proposed theoretical framework to quantify four-photon indistinguishability, as well as to obtain bounds on three unmeasured two-photon overlaps. Our findings are in high agreement with the theory, and represent a new resource-effective technique for the characterization of multiphoton interference.

Taira Giordani, Daniel J. Brod, Chiara Esposito, Niko Viggianiello, Marco Romano, Fulvio Flamini, Gonzalo Carvacho, Nicolò Spagnolo, Ernesto F Galvão and Fabio Sciarrino. New Journal of Physics 22, 043001- Published April 2020

Link: https://iopscience.iop.org/article/10.1088/1367-2630/ab7a30