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Table 1 List of parameters and values for which we assigned fixed values. Justification of these values is given in Sect. 3

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