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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





Diameter of active detector area on CubeSat

20 μm


OGS telescope diameter

30 cm


CubeSat telescope diameter

10 cm


Probability of noise count to be correct



Probability of erroneous detection


\(E^{\mathit {max}}_{\mathit {E}91/\mathit {DSP}}\)

Maximum tolerable QBER for E91/DSP

10.2% /6.2%


OGS multiplexed SNSPD efficiency (E91 only)

70% (−1.5 dB)


CubeSat detector efficiency

15% (−8.2 dB)


Error correction protocol efficiency



Effective focal length CubeSat telescope

40 cm

\(f_{\mathit {SYN}}\)

Repetition rate of OGS’s beacon laser

10 MHz


Field of view CubeSat (full angle)

50 μrad


Signal photon wavelength

810 nm


Total loss

−62.7 dB (max)


Total loss OGS arm (source to detector) (E91 only)

60% (−2.3 dB)


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)


\(\mu_{\mathit {E}91}\)

Mean photon number per coincidence window (E91 only)



Fried parameter

5 cm–40 cm


OGS count rate (E91 only)

60 Mcps


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


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


OGS pointing precision (rms, full angle)

2.4 μrad


CubeSat pointing precision (rms, full angle)

40 μrad


Combined OGS detectors + time tagging jitter

16 ps


CubeSat detector + time tagging jitter

37 ps


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