The detector you forgot was measuring.
For sixty years, photon-counting has assumed the detector is a neutral observer. In superconducting circuits it is not. DFCBL-CAL reveals the distortion your detector adds, and corrects it, from a single network-analyser sweep.
The problem
Every readout counts photons. The detector's share is never subtracted.
Every superconducting quantum computer, sensor and communication system reads out its state by counting photons. Standard calibration corrects only for efficiency and dark counts, and assumes the detector itself is transparent. It is not: a superconducting detector's own electrical impedance can distort the very statistics being measured, and that error is currently going uncorrected.
Calibration stops short
Efficiency and dark counts are corrected; the detector's electrical impedance is assumed away.
Distortion hides in your statistics
Part of the measured sideband structure is the detector, not the physics you are studying.
Disagreement that survives calibration
Each laboratory's detector differs, so results disagree in ways standard calibration cannot reconcile.
How it works
Four steps, from one sweep to corrected statistics.
01
Characterise
One network-analyser sweep of your detector port. Equipment you already run.
02
Diagnose
DFCBL-CAL computes a single detector-health number, Λ_d, telling you whether distortion is significant.
03
Correct
It removes the detector's imprint from your photon-counting data, recovering detector-independent statistics.
04
Report
You get corrected measurements plus a documented record of what the detector contributed.
Who it is for
Built for anyone whose measurement passes through a superconducting detector.
Quantum computing teams
Screen every readout detector for distortion; recover cleaner qubit-readout data on hardware you already own.
Single-photon source and QKD makers
Certify the true statistics of your source, with the detector contribution separated out and documented.
Research laboratories
Resolve cross-setup disagreement on photon statistics; publish your detector characterisation alongside your data for reproducibility.
Metrology and standards
A defined detector-quality metric and reporting format, suitable for inter-laboratory comparison.
Available now
Available now: early-access software.
DFCBL-CAL is available today as an early-access analysis toolkit for superconducting-detector laboratories. It runs on standard cryogenic-measurement data and requires no new hardware. We are onboarding a small number of laboratories directly, with hands-on support, rather than through open self-serve download.
To request access, discuss your setup, or arrange an evaluation, contact licensing@physivitis.tech.
Validation status
Where the science stands
DFCBL-CAL rests on a framework whose predictions and correction have been verified in numerical simulation, and whose mathematical consistency, including its reduction to standard photodetection theory in the appropriate limits, has been demonstrated.
Validation on physical hardware is the current step, and we are candid that it is not yet complete. The toolkit is therefore offered as a diagnostic and correction tool: the underlying impedance measurement is standard and reliable, and the correction is applied for your evaluation.
Every early-access laboratory contributes to, and benefits from, the ongoing hardware validation.
UK patent application filed: GB2613792.7.
Validation partners
Validation partners welcome
We are actively seeking laboratories with cryogenic photon-counting capability, national metrology institutes, university circuit-QED groups, and quantum hardware companies, to run the validation campaign on real detectors. The measurement is modest in scope for a suitably equipped laboratory, and joint publication is anticipated. If you have a dilution refrigerator and an interest, we would like to hear from you.
Discuss a validation collaborationFind out what your detector is really measuring.
Early access is open to superconducting-detector laboratories now.
Request early accessDFCBL-CAL: detector calibration for quantum photon counting. UK patent application filed: GB2613792.7. Early access; enquiry-based onboarding.