Fig. 3: Two-level quantum interferences.
From: Quantum state processing through controllable synthetic temporal photonic lattices
a,d, Spatial representation of two roundtrips of the DTQW in the coupled fibre-loop system under uncontrolled (a) and controlled (d) schemes. The legend in the centre introduces the action of the three operators used in the experiment (Fourier (50:50), transmission and reflection). b,e, Single-photon histograms obtained through the uncontrolled (b) and controlled (e) schemes. The light-blue box in the single-photon histogram represents the interference coincidence window at zero relative time delay taken from the central interference bin. c,f, Normalized coincidence counts of entangled photons and classical light intensity (blue squares and grey circles, respectively) as a function of the relative phase difference (θ) between the time bins, yielding two-photon quantum interference patterns for the uncontrolled (c) and controlled (f) schemes. Experimental measurements are fitted with theoretical models (blue solid line for entangled qubits and dashed grey line for classical light). From two-photon quantum interference measurements, raw visibility values of Vd=2 = 97.82% and V′d=2 = 96.83% were extracted for the uncontrolled (c) and controlled (f) schemes, respectively.
