Figure 4
(a) Experimental measurement of a single-photon fringe pattern for input mode 1 and output mode 2 as a function of the dissipated power. Points: normalized counts. Solid red curve: best fit of the measured data with a sinusoidal function. Horizontal red line: estimated contribution of accidental coincidences. (b) Experimental fringe pattern for a two-photon input 
as a function of the dissipated power. Blue points: normalized coincidences of the output (1, 1), with one photon for each output port; the statistics of the recorded data was ∼1200 coincidences for the fringe maximum in 120 s. Green points: normalized coincidences of the output (0, 2), with two photons on output port 2; the statistics of the recorded data was ∼600 coincidences for the fringe maximum in 180 s. Both fringes show twice the periodicity of single-photon ones (dashed red curve). Solid lines: best fit of the measured data with a sinusoidal function. Horizontal blue and green lines: estimated contribution of accidental coincidences. The error bars are given by Poissonian statistics.
