Fig. 2: Scheme of the experimental apparatus.
From: Reconfigurable continuously-coupled 3D photonic circuit for Boson Sampling experiments
a A parametric down-conversion process in a Beta-Barium Borate crystal generates one- and two-pair photon states. Generation in the single-pair regime is employed for the unitary reconstruction procedures, while 3- and 4-photon states are employed for experiments in the Boson Sampling framework. Photons are prepared in their polarization and temporal degrees of freedom before coupling in the input single-mode fiber array. After evolution, photons are finally detected via a set of 32 single-photon avalanche photodiodes connected to a 32-channel time-to-digital converter for the reconstruction of the coincidence pattern. b Schematic of the in- and out-coupling of the single photons with the 3D photonic circuit: one- and two-dimensional fiber arrays connect to the fan-in and fan-out sections of the circuit. Legend: BBO beta-barium borate crystal, BPF band-pass filter, HWP half-wave plate, PBS polarizing beamsplitter, PC polarization controller, DL delay line, PS power supply, TDC time-to-digital converter, 1D-/2D-FA one-/two-dimensional fiber array, FI fan-in, FO fan-out, CCWL continuously-coupled waveguide lattice, RS resistors.
