Towards Measuring Terahertz Photon Statistics by a Superconducting Bolometer.

Area of Science:

• Solid-state physics
• Quantum optics
• Terahertz (THz) technology

Background:

• Superconducting bolometers are sensitive detectors used in various scientific applications.
• Understanding the fundamental detection mechanisms of these devices is crucial for advancing quantum measurements.
• Terahertz (THz) photon detection involves complex interactions that require detailed statistical analysis.

Purpose of the Study:

• To investigate the statistical distributions of analog readings from a superconducting bolometer under THz photon irradiation.
• To reveal the discrete nature of THz photon detection by superconducting bolometers.
• To establish a relationship between the quantum statistics of incident photons and the bolometer's continuous output.

Main Methods:

• Utilizing an antenna-coupled THz superconducting bolometer (niobium nitride film).
• Irradiating the bolometer with low-energy THz photon fluxes exhibiting Poisson statistics.
• Generating THz photons via parametric down-conversion in a lithium niobate crystal within a cryostat.
• Analyzing experimental histograms and applying theoretical approximations.

Main Results:

• Bolometer readings per pulse consist of discrete counts, termed "single charges."
• The mean number of "single charges" is linearly dependent on the input photon number.
• Contributions of "single counts" to the total analog reading follow a normal distribution.
• A general formula was proposed to link continuous bolometer readings with discrete photon statistics.

Conclusions:

• The study confirms the discrete quantum nature of THz detection in superconducting bolometers.
• The findings pave the way for studying the quantum characteristics of these detectors.
• The proposed formula provides a framework for understanding THz photon detection at the quantum level.