Workbench tool

MDI-QKD relay estimator

Estimate two-arm loss, relay coincidence probability, QBER, and asymptotic key-rate intuition for a measurement-device-independent QKD teaching setup.

Shareable URL state

Keep the current calculator inputs in the URL so this teaching setup can be reopened or shared without exporting files.

Only model inputs are stored in the link. No keys or telemetry are added.

PresetRelay modelBoth options remain teaching approximations; the relay report channel is still assumed to be authenticated.Alice arm lengthkmBob arm lengthkmFiber attenuationdB/kmAlice connector lossdBBob connector lossdBPulse rateHzAlice mean photon numbermuBob mean photon numbermuRelay detector efficiencyRelay dark count probabilityBackground count probabilityInterference visibilityCaptures phase/reference alignment and mode-overlap quality as one scalar teaching knob.Misalignment errorBell-state measurement efficiencyBasis sifting factorReconciliation efficiencyBlock sizepulses

Total span

50km

Coincidence probability

0.0614%

QBER proxy

3.46%

Secret-key-rate proxy

163,229Hz

Alice arm loss

8dB

Bob arm loss

8dB

Arm symmetry

100%

1.0 is perfectly balanced.

Interference penalty

97%

Relay accounting

Alice relay detection

3.54%

Bob relay detection

3.54%

Joint signal probability

0.0608%

Relay noise probability

0.0006%

Bell announcements

614per block

Sifted bits

307per block

Symmetric total-distance sweep

totalDistanceKm spans 0.00 to 90.0 while secretKeyRateHz spans 1.67e+4 to 1.62e+6. Midpoint sample: totalDistanceKm 45.0, secretKeyRateHz 2.08e+5.

Distance vs QBER proxy (%)

totalDistanceKm spans 0.00 to 90.0 while qber spans 3.05 to 5.70. Midpoint sample: totalDistanceKm 45.0, qber 3.37.

Warnings and cautions

info: The relay is treated as untrusted for detector security intuition, but announcement integrity and source-state characterization are still assumed.

Formulas and assumptions

This MDI-QKD slice is a teaching estimator for two-arm weak-coherent-state links into a middle Bell-state-measurement relay.
The relay may be untrusted with respect to detector side channels, but the estimator still assumes Alice and Bob can authenticate the classical announcement channel.
Two-photon interference, decoy-state optimization, finite-key security proofs, source leakage, and phase-reference calibration are compressed into scalar visibility, efficiency, and QBER proxies.
Secret-key output is an asymptotic teaching lower-bound proxy. It is not a certified MDI-QKD implementation proof or deployment-grade performance guarantee.
Each arm uses eta = 10^(-loss_dB / 10) with separate Alice and Bob loss budgets into the middle relay.
Joint Bell-state announcements scale with both arm detection probabilities, a scalar Bell-state-measurement efficiency, and an interference penalty based on visibility and arm symmetry.
Noise combines relay dark and background counts, then contributes a random-bit 50% error term in the coincidence proxy.

References

Lo, Curty, and Qi (2012) measurement-device-independent QKD.
Tamaki et al. and related MDI-QKD reviews for interference-visibility and source-assumption context.

Tools

Engineering and research workbench

Loading the selected calculator, defaults, and scientific caution notes.

Preparing tool

Loading workbench view

Preparing calibrated controls, default presets, and explanatory notes.

Workbench tool

MDI-QKD relay estimator

Estimate two-arm loss, relay coincidence probability, QBER, and asymptotic key-rate intuition for a measurement-device-independent QKD teaching setup.

Shareable URL state

Keep the current calculator inputs in the URL so this teaching setup can be reopened or shared without exporting files.

Only model inputs are stored in the link. No keys or telemetry are added.

Total span

50km

Coincidence probability

0.0614%

QBER proxy

3.46%

Secret-key-rate proxy

163,229Hz

Alice arm loss

8dB

Bob arm loss

8dB

Arm symmetry

100%

1.0 is perfectly balanced.

Interference penalty

97%

Relay accounting

Alice relay detection

3.54%

Bob relay detection

3.54%

Joint signal probability

0.0608%

Relay noise probability

0.0006%

Bell announcements

614per block

Sifted bits

307per block

Symmetric total-distance sweep

totalDistanceKm spans 0.00 to 90.0 while secretKeyRateHz spans 1.67e+4 to 1.62e+6. Midpoint sample: totalDistanceKm 45.0, secretKeyRateHz 2.08e+5.

Distance vs QBER proxy (%)

totalDistanceKm spans 0.00 to 90.0 while qber spans 3.05 to 5.70. Midpoint sample: totalDistanceKm 45.0, qber 3.37.

Warnings and cautions

info: The relay is treated as untrusted for detector security intuition, but announcement integrity and source-state characterization are still assumed.

Formulas and assumptions

This MDI-QKD slice is a teaching estimator for two-arm weak-coherent-state links into a middle Bell-state-measurement relay.
The relay may be untrusted with respect to detector side channels, but the estimator still assumes Alice and Bob can authenticate the classical announcement channel.
Two-photon interference, decoy-state optimization, finite-key security proofs, source leakage, and phase-reference calibration are compressed into scalar visibility, efficiency, and QBER proxies.
Secret-key output is an asymptotic teaching lower-bound proxy. It is not a certified MDI-QKD implementation proof or deployment-grade performance guarantee.
Each arm uses eta = 10^(-loss_dB / 10) with separate Alice and Bob loss budgets into the middle relay.
Joint Bell-state announcements scale with both arm detection probabilities, a scalar Bell-state-measurement efficiency, and an interference penalty based on visibility and arm symmetry.
Noise combines relay dark and background counts, then contributes a random-bit 50% error term in the coincidence proxy.

References

Lo, Curty, and Qi (2012) measurement-device-independent QKD.
Tamaki et al. and related MDI-QKD reviews for interference-visibility and source-assumption context.