The results achieved in this work are compared with other integrated quantum photonics platforms using two metrics, waveguide optical loss and source brightness 8 , 9 , 10 , 17 , 30 , 35 , 36 , 37 , 38 , 39 , 40 , 41 . The source brightness metric has been frequently used in this context. The waveguide loss metric is of critical importance for integrated quantum systems as it impacts quantum state transport across the semiconductor chip. The brightness was calculated from the maximum reported pair generation rate divided by the spectral span (from the resonator total quality factor). The waveguide loss was estimated from the resonator intrinsic quality factor, if not reported. The plot shows both SFWM (red points) and SPDC (blue points) processes. The pump powers used in the references are as follows: 1.5 mW (this work), 13.4 W (ref. 8 ), 0.45 mW (ref. 9 ), 2.3 mW (ref. 10 ), 0.43 mW (ref. 17 ), 0.45 mW (ref. 30 ), 25 W (ref. 35 ), 60 W (ref. 36 ), 2.0 mW (ref. 37 ), 6.2 mW (ref. 38 ), 22 W (ref. 39 ), 1.2 W (ref. 40 ) and 0.33 mW (ref. 41 ). Inset, conceptual figure for an integrated photonic SPDC source featuring a single integrated near-infrared (telecom) DFB pump that is frequency-doubled (SHG) by a high- Q Si 3 N 4 resonator to provide the near-visible pump for a high- Q Si 3 N 4 resonator SPDC source. DFB, distributed feedback laser; FH, first harmonic; NIR, near-infrared; SH, second harmonic.
