How DFCBL-CAL works
One sweep to characterise the detector; one correction, applied to every measurement that follows.
The assumption that breaks
Standard theory treats the detector as an ideal absorber.
In standard photodetection theory, the detector is assumed to be transparent to the statistics it measures: it counts photons without influencing them. That assumption holds for the regimes the theory was built on.
A superconducting detector is different. Its own electrical impedance is part of the measurement chain, and in superconducting circuits that impedance can distort the very photon statistics the detector is supposed to observe. The distortion is real, it is systematic, and today it is going uncorrected.
Watch the walkthrough
The distortion, the sweep, the correction. Narrated, step by step.
A narrated illustrative walkthrough of the method. It plays like a video, loops automatically, and you can pause, mute or scrub at any time.
Illustrative walkthrough, not the production tool
Scene 1 of 6 · The Hidden Distortion
Standard theory assumes the detector is transparent. In superconducting circuits, its impedance distorts the statistics it measures.
The two-step method
Characterise once, apply every time.
1. Characterise
A one-time network-analyser sweep of the detector port. From that sweep, DFCBL-CAL derives the correction and the Λ_d detector-health number.
2. Apply
On every subsequent measurement, the correction is applied to your photon-counting data, recovering detector-independent statistics.
The correction is derived from the sweep, not fitted to your data. The detailed construction of the correction and the Λ_d formula are proprietary, and are disclosed under NDA.
What you get
- Corrected observables: your counting data with the detector contribution removed.
- The Λ_d number: a single detector-health figure that tells you how significant the distortion is.
- A documented detector-contribution record, for reporting, audit and reproducibility.
What it does not require
- No new hardware: the characterisation uses the network-analyser equipment you already run.
- No source changes: the correction applies to your existing measurement arrangement.
- No new measurement campaign: standard cryogenic-measurement data is all the input it needs.
Industries of interest
Who benefits, and how.
Quantum computing
Cleaner qubit-readout statistics on hardware you already own, with every readout detector screened for distortion.
Quantum communications and QKD
Certified true source statistics, with the detector contribution separated out and documented.
Circuit-QED research groups
An end to cross-setup disagreement on photon statistics, with detector characterisation publishable alongside the data.
Metrology and standards bodies
A defined detector-quality metric and reporting format, suitable for inter-laboratory comparison.
Cryogenic sensing
Faint-signal measurements, from dark-matter searches to microwave photon counting, with the detector imprint removed.
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.
See what your detector adds.
Request early access, or talk to us about running the validation campaign on your detectors.