Fig. 3: Results of correlated and energy–time entangled photon-pairs.
From: High-performance quantum entanglement generation via cascaded second-order nonlinear processes
a Photon-counting rate (black circle) in signal channel versus pump power. The black solid line is the quadratic polynomial fitting curve of the photon-counting rate with the quadratic and linear parts shown as the red and blue curves, respectively. The error bars are estimated by Poissonian photon-counting statistics. b Measured CAR versus pump power. The error bars are estimated from the statistical errors of the coincidence and accidental coincidence counts, in which the former is obtained by assuming Poissonian statistics and the latter is estimated by the standard deviation values of accidental coincidence in three 300-ps time windows away from the coincidence peak. The inset is the coincidence histogram between signal and idler photons when the pump power is set at ~2 mW, and a coincidence window of 300 ps is marked. c Results of Franson interference for β = −1.57 (red circle) and β = −0.64 (blue rectangle). d Results of two-photon interference (red circle) and single-photon interference (blue rectangle). The error bars of coincidence count in (c, d) are estimated by repeating the measurement three times, while the error bars of photon counts in (d) are obtained by Poissonian photon-counting statistics.
