Three-photon bosonic coalescence in an integrated tritter

Abstract

The main features of quantum mechanics reside in interference deriving from the superposition of different quantum states. While current quantum optical technology enables two-photon interference both in bulk and integrated systems, simultaneous interference of more than two particles, leading to richer quantum phenomena, is still a challenging task. Here we report the experimental observation of three-photon interference in an integrated three-port directional coupler realized by ultrafast laser writing. By exploiting the capability of this technique to produce three-dimensional structures, we realized and tested in the quantum regime a three-port beam splitter, namely a tritter, which allowed us to observe bosonic coalescence of three photons. These results open new important perspectives in many areas of quantum information, such as fundamental tests of quantum mechanics with increasing number of photons, quantum state engineering, quantum sensing and quantum simulation.

Sampling of partially distinguishable bosons and the relation to the multidimensional permanent

“…[18,35], formalized in Ref. [45] and taken further in this article overcomes the issues enumerated in Section II B: Since our central Eq.…”

“…The computation of event probabilities in Ref. [35] was implicitly based on this approach, and a similar projection operator is also used in Ref. [48].…”

“…For distinguishable particles, one speaks of classical sampling, which can be simulated inexpensively with a naive Monte-Carlo method that treats particles independently, one after another [5,11]. When artificial symmetries structure the scattering matrix, selection rules efficiently predict the strict suppression of certain output events [5,35]. In these examples, physical intuition and the understanding of computational complexity nicely complement each other [36].…”

Generalized Quantum Fast Transformations via Femtosecond Laser Writing Technique

“…In [13], one first experimental realization of a quantum walk implementing the qFFT has been reported as an effective platform for validating genuine quantum interference with many-photon states. The implementation of the qFFT interferometer has been realized on a photonic integrated platform by exploiting the 3-D capabilities of femtosecond laser writing technology [17,18], which enables the fabrication of quantum walks arranged in three-dimensional scalable architectures with arbitrary layouts [20][21][22][23]. Indeed, the integration of all beamsplitters and phase shifters into a monolithic structure leads to a fundamental increase in the stability and scalability of the whole apparatus.…”

Suppression laws for multiparticle interference in Sylvester interferometers

“…The simplest case is the Hong-Ou-Mandel (HOM) effect when two particles impinge on distinct ports of a balanced beam splitter: quantum interference suppresses the coincident output (one particle per each output) in the case of bosons and the single-port output (both particles in either output) in case of fermions. In the multi-particle case, a sort of generalised HOM effect occurs for symmetric multiport beam splitters [5][6][7][8]. In particular, Tichy et al [7] showed that for a particular class of multiports, namely Bell or Fourier multiports, and input states with cyclic symmetry, a full suppression of most of the output combinations is observed; a * andrea.crespi@polimi.it simple analytical law gives a sufficient criterion for such suppression.…”