Table 2.
Comparison of representative photon sources
| Type | SPDC (Bulk) [31] | SPDC (Waveguide) [157, 158] | SFWM (Si-PIC) [51] | Quantum Dot (InAs) [57] |
|---|---|---|---|---|
| Output State | TMSV/HSPS | TMSV/HSPS | TMSV/HSPS | Single Photon |
| (Probabilistic) | (Probabilistic) | (Probabilistic) | (Deterministic) | |
| Loss | 0.37 dB | 3.2–5.2 dB | > 1 dB | 1.4 dB |
| Brightness | 3.9 × 103 pairs/mW | 3.5 − 5.6 × 106 cps/mW | ~ 106 cps/mW2* | 1.8 × 107 cps** |
| Source-to-source (Single-source) indistinguishability | 0.986 | – (0.945) | 0.995 | –***(0.986) |
| Wavelength | 1550 nm | 1540 nm | 1550 nm | 884 nm |
| Bandwidth | ~ 500 GHz | ~ 1 THz | ~ 6 GHz | 2.1 GHz |
| Temperature | 300 K | 300 K | 2.2 K (to 300 K)**** | < 10 K |
| Advantages | Low loss | High efficiency | Scalability | Deterministic generation |
| Challenges | Scalability, Multi-photon generation | Loss, Multi-photon generation | Loss, Multi-photon generation | Inhomogeneity |
* Estimated from similar Si-PIC ring resonator sources [176]
** The value is limited by detector count rates
*** 69% source-to-source indistinguishability has been reported in [61]
**** The experiment was performed at 2.2 K due to the integrated SNSPDs, but the source itself may not require cryogenic cooling