From: Q3Sat: quantum communications uplink to a 3U CubeSat—feasibility & design
Symbol | Parameter | Value |
---|---|---|
\(d_{B}\) | Diameter of active detector area on CubeSat | 20 μm |
\(D_{A}\) | OGS telescope diameter | 30 cm |
\(D_{B}\) | CubeSat telescope diameter | 10 cm |
\(e_{0}\) | Probability of noise count to be correct | 50% |
\(e_{d}\) | Probability of erroneous detection | 2% |
\(E^{\mathit {max}}_{\mathit {E}91/\mathit {DSP}}\) | Maximum tolerable QBER for E91/DSP | 10.2% /6.2% |
\(\eta_{A}\) | OGS multiplexed SNSPD efficiency (E91 only) | 70% (−1.5 dB) |
\(\eta_{B}\) | CubeSat detector efficiency | 15% (−8.2 dB) |
f | Error correction protocol efficiency | 1.1 |
\(f_{B}\) | Effective focal length CubeSat telescope | 40 cm |
\(f_{\mathit {SYN}}\) | Repetition rate of OGS’s beacon laser | 10 MHz |
FoV | Field of view CubeSat (full angle) | 50 μrad |
λ | Signal photon wavelength | 810 nm |
Λ | Total loss | −62.7 dB (max) |
\(\Lambda_{A}\) | Total loss OGS arm (source to detector) (E91 only) | 60% (−2.3 dB) |
\(\Lambda_{H}\) | Heralding efficiency (E91 only) | 85% (−0.7 dB) |
\(\Lambda_{\mathit {TA}}\) | OGS telescope loss (only E91) | −1.0 dB |
\(\Lambda_{\mathit {TB}}\) | CubeSat telescope loss | −1.5 dB |
\(\Lambda_{\mathit {OB}}\) | CubeSat optical elements loss | −1.0 dB |
\(\Lambda_{\mathit {PB}}\) | CubeSat pointing loss | −2.5 dB |
\(\Lambda_{\mathit {SB}}\) | CubeSat basis switch loss | −0.5 dB |
\(\Lambda_{\mathit {SYN}}\) | Loss due to errors in clock sync. | −0.5 dB |
\(\mu_{\mathit {DSP}}\) | Mean photon number per signal pulse (DSP only) | 0.64 |
\(\mu_{\mathit {E}91}\) | Mean photon number per coincidence window (E91 only) | 0.01 |
\(r_{0}\) | Fried parameter | 5 cm–40 cm |
\(R_{A}\) | OGS count rate (E91 only) | 60 Mcps |
\(R_{B}\) | CubeSat count rate (including noise) | 3 kcps (max) |
\(R_{B}^{\mathit {max}}\) | CubeSat detectors’ maximum count rate | 100 kHz |
\(R_{\mathit {BG}}\) | CubeSat background counts (total) | 80–180 cps |
\(R_{\mathit {DC}}\) | CubeSat dark count rate (per detector) | 200 cps |
\(R_{B+D}\) | CubeSat total noise counts | 480–580 cps |
\(R^{P}_{\mathit {DSP}}\) | Effective signal photon rate (DSP only) | 315 Mcps |
\(R^{P}_{\mathit {E}91}\) | Pair rate of entangled photon source (E91 only) | 100 Mcps |
\(R_{\mathit {rep}}\) | Repetition rate of single photon source (DSP only) | 1 GHz |
\(\sigma_{A}\) | OGS pointing precision (rms, full angle) | 2.4 μrad |
\(\sigma_{B}\) | CubeSat pointing precision (rms, full angle) | 40 μrad |
\(t_{A}\) | Combined OGS detectors + time tagging jitter | 16 ps |
\(t_{B}\) | CubeSat detector + time tagging jitter | 37 ps |
τ | Coincidence window | 80 ps |
\(t_{\mathit {SB}}\) | CubeSat basis switching time | 100 μs |
\(t_{\mathit {TT}}\) | Time tagging resolution (on board CubeSat) | 10 ps |
\(t_{\mathit {MD}}\) | Measurement duration of each chunk for clock sync. | 100 ms |
\(t_{\mathit {QC}}\) | Maximum duration of quantum connection per pass | 220 s |