Testing Higher-Order Quantum Interference with Many-Particle States published in Phys. Rev. Lett.

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Our Article Testing Higher-Order Quantum Interference with Many-Particle States has been published in Physical Review Letters:

Phys. Rev. Lett. 126, 190401 (2021)


Quantum theory permits interference between indistinguishable paths but, at the same time, restricts its order. Single-particle interference, for instance, is limited to the second order, that is, to pairs of single-particle paths. To date, all experimental efforts to search for higher-order interferences beyond those compatible with quantum mechanics have been based on such single-particle schemes. However, quantum physics is not bound to single-particle interference. We here experimentally study many-particle higher-order interference using a two-photon-five-slit setup. We observe nonzero two-particle interference up to fourth order, corresponding to the interference of two distinct two-particle paths. We further show that fifth-order interference is restricted to 10-3 in the intensity-correlation regime and to 10-2 in the photon-correlation regime, thus providing novel bounds on higher-order quantum interference.