Fig. 4: Results of frequency-bin and time-bin entangled photon-pairs.
From: High-performance quantum entanglement generation via cascaded second-order nonlinear processes
a Spatial quantum beating of frequency-bin entangled state. b, c The real and the imaginary parts of the experimentally reconstructed density matrix of frequency-bin entangled photon-pairs, respectively. d The phase α + β dependence of the threefold coincidence between the synchronous electrical signal and the photons from the ports A1&B1 (red rectangle), A1&B2 (blue triangle), A2&B1 (purple inverted triangle), or A2&B2 (green circle). e Correlation coefficient E(α,β) calculated from the four curves in d according to Eq. (2). f, g The real and the imaginary parts of the density matrix of time-bin entangled photon-pairs, respectively. The error bars in a and d are all estimated from measurement results assuming Poissonian statistics, while the error bars in e are obtained via propagation of statistical errors according to Eq. (2).
