Fig. 5: High-dimensional quantum interference.

a Schematic of the measurement setup for high-dimensional Hong-Ou-Mandel effect. ODL, optical delay line; BS: beamsplitter; PF: programmable filter. b Normalized coincidence rate between the two SNSPDs with photon pairs in the degenerate resonance. c Normalized coincidence rate between the two SNSPDs with photon pairs from first five resonance pairs. Theoretical envelop of the coincidence rate is also plotted. d Measured coincidence rate (black dot) and theoretical calculation (red) near zero time delay in (c). e Measured coincidence rate (black dot) and theoretical calculation (blue) at time delay around 1.1 ns in (c). Error bars are estimated by assuming the Poisson distribution of photon counting.