Workbench tool

Twin-field QKD estimator

Estimate middle-station interference, phase-stability penalties, and a cautious secret-key-rate proxy for a twin-field 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.

PresetMiddle-station modelBoth options remain teaching approximations; authenticated classical coordination is still assumed.Alice arm lengthkmBob arm lengthkmFiber attenuationdB/kmAlice connector lossdBBob connector lossdBPulse rateHzAlice mean photon numbermuBob mean photon numbermuMiddle-station detector efficiencyDark count probabilityBackground count probabilityInterference visibilityBundles mode overlap and coherent interference quality into one scalar teaching control.Phase tracking efficiencyProxy for reference dissemination, drift compensation, and servo quality.RMS phase errorradHigher sigma directly suppresses the interference term through exp(-sigma^2 / 2).Accepted phase-window fractionTeaching proxy for phase-slice post-selection or accepted matching windows.Basis sifting factorReconciliation efficiencyBlock sizepulses

Total span

150km

Middle-station click probability

0.0779%

QBER proxy

3.42%

Secret-key-rate proxy

126,817Hz

Phase stability factor

95.3%

Interference penalty

93.9%

Arm symmetry

100%

1.0 is perfectly balanced.

Single-photon weight proxy

26.8%

Middle-station accounting

Alice arm loss

16dB

Bob arm loss

16dB

Alice arrival probability

0.361%

Bob arrival probability

0.361%

Signal probability

0.0773%

Noise probability

0.0006%

Click rate

389,268Hz

Accepted windows

850000per block

Sifted bits

330per block

Total distance vs secret-key-rate proxy

totalDistanceKm spans 0.00 to 230 while secretKeyRateHz spans 2.08e+4 to 2.83e+6. Midpoint sample: totalDistanceKm 115, secretKeyRateHz 2.66e+5.

Total distance vs QBER proxy (%)

totalDistanceKm spans 0.00 to 230 while qber spans 3.08 to 4.89. Midpoint sample: totalDistanceKm 115, qber 3.24.

Distance vs phase-stability factor (%)

totalDistanceKm spans 0.00 to 230 while phaseStabilityFactor spans 95.3 to 95.3. Midpoint sample: totalDistanceKm 115, phaseStabilityFactor 95.3.

Warnings and cautions

info: The middle station is treated as untrusted for measurement intuition, but authenticated announcements and characterized source states are still assumed.

Formulas and assumptions

This twin-field QKD slice is a teaching estimator for weak coherent states interfering at a middle station with scalar phase-stability controls.
Decoy-state optimization, phase-reference leakage analysis, finite-key proofs, and detector calibration are compressed into visibility, phase-tracking, and post-selection proxies.
The middle station may be treated as untrusted for measurement intuition, but authenticated classical coordination and characterized transmitters are still assumed.
Reported secret-key output is a non-certified teaching proxy for intuition about phase-sensitive long-distance scaling. It is not a deployment-grade TF-QKD proof.
Each arm uses eta = 10^(-loss_dB / 10) with separate Alice and Bob loss budgets into the middle station.
Phase stability is compressed into eta_phase = eta_track exp(-sigma_phi^2 / 2), where sigma_phi is an RMS phase-error proxy in radians.
The middle-station signal term scales with a single-photon weight proxy, average arm arrival probability, interference visibility, symmetry, and accepted phase-post-selection windows.

References

Lucamarini et al. twin-field QKD.
Twin-field QKD review literature for phase-reference distribution, post-selection, and decoy-analysis caveats.

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

Twin-field QKD estimator

Estimate middle-station interference, phase-stability penalties, and a cautious secret-key-rate proxy for a twin-field 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

150km

Middle-station click probability

0.0779%

QBER proxy

3.42%

Secret-key-rate proxy

126,817Hz

Phase stability factor

95.3%

Interference penalty

93.9%

Arm symmetry

100%

1.0 is perfectly balanced.

Single-photon weight proxy

26.8%

Middle-station accounting

Alice arm loss

16dB

Bob arm loss

16dB

Alice arrival probability

0.361%

Bob arrival probability

0.361%

Signal probability

0.0773%

Noise probability

0.0006%

Click rate

389,268Hz

Accepted windows

850000per block

Sifted bits

330per block

Total distance vs secret-key-rate proxy

totalDistanceKm spans 0.00 to 230 while secretKeyRateHz spans 2.08e+4 to 2.83e+6. Midpoint sample: totalDistanceKm 115, secretKeyRateHz 2.66e+5.

Total distance vs QBER proxy (%)

totalDistanceKm spans 0.00 to 230 while qber spans 3.08 to 4.89. Midpoint sample: totalDistanceKm 115, qber 3.24.

Distance vs phase-stability factor (%)

totalDistanceKm spans 0.00 to 230 while phaseStabilityFactor spans 95.3 to 95.3. Midpoint sample: totalDistanceKm 115, phaseStabilityFactor 95.3.

Warnings and cautions

info: The middle station is treated as untrusted for measurement intuition, but authenticated announcements and characterized source states are still assumed.

Formulas and assumptions

This twin-field QKD slice is a teaching estimator for weak coherent states interfering at a middle station with scalar phase-stability controls.
Decoy-state optimization, phase-reference leakage analysis, finite-key proofs, and detector calibration are compressed into visibility, phase-tracking, and post-selection proxies.
The middle station may be treated as untrusted for measurement intuition, but authenticated classical coordination and characterized transmitters are still assumed.
Reported secret-key output is a non-certified teaching proxy for intuition about phase-sensitive long-distance scaling. It is not a deployment-grade TF-QKD proof.
Each arm uses eta = 10^(-loss_dB / 10) with separate Alice and Bob loss budgets into the middle station.
Phase stability is compressed into eta_phase = eta_track exp(-sigma_phi^2 / 2), where sigma_phi is an RMS phase-error proxy in radians.
The middle-station signal term scales with a single-photon weight proxy, average arm arrival probability, interference visibility, symmetry, and accepted phase-post-selection windows.

References

Lucamarini et al. twin-field QKD.
Twin-field QKD review literature for phase-reference distribution, post-selection, and decoy-analysis caveats.