Absolute calibration of a variable attenuator using few-photon pulses

Area of Science:

• Quantum optics
• Photonics
• Superconducting detector technology

Background:

• Accurate calibration of optical attenuators is crucial for many photonic applications.
• Traditional calibration methods require high photon fluxes and external references, limiting their use at low light levels.
• Superconducting Transition Edge Sensors (TES) offer photon-number resolving capabilities, enabling new calibration approaches.

Purpose of the Study:

• To demonstrate a novel method for calibrating variable optical attenuators directly at the few-photon level.
• To leverage the linearity and photon-number resolving nature of TES detectors for precise attenuation measurements.
• To validate the few-photon calibration method against conventional techniques.

Main Methods:

• Utilized a superconducting Transition Edge Sensor (TES) for direct few-photon level detection.
• Employed the Poisson-Influenced K-Means Algorithm (PIKA) to determine mean photon numbers per pulse and their uncertainties.
• Compared calibration results with a conventional method using analog detectors at higher photon fluxes.

Main Results:

• Successfully calibrated optical attenuators directly at the few-photon level (0.15 to 18 photons per pulse).
• Achieved agreement between few-photon calibration and conventional methods within experimental uncertainties.
• Demonstrated robustness of the method despite optical power drifts during the experiment.

Conclusions:

• The TES-based few-photon calibration method is accurate and requires no external calibration.
• This technique provides reliable attenuation measurements even under challenging experimental conditions.
• The PIKA algorithm effectively extracts photon statistics for precise calibration.