Photon number adaptive single-photon detection with time-walk passive compensation.

Area of Science:

• Optical physics
• Quantum optics
• Precision measurement

Background:

• Long-distance laser time transfer (e.g., satellite-to-satellite, satellite-to-ground) relies on accurate photon pulse flight time measurement.
• The time walk phenomenon, caused by variations in incident photon numbers, significantly compromises measurement accuracy.

Purpose of the Study:

• To propose and validate a novel single-photon detection method that adaptively compensates for the time walk effect.
• To enhance the precision of laser time transfer in dynamic environments with fluctuating photon numbers.

Main Methods:

• A fiber ring is employed to divide incident photon pulses into attenuated pulse trains.
• Each pulse in the train is separated by equal time intervals and undergoes equal attenuation.
• The final pulse in the train is attenuated to a single-photon level, minimizing time walk.

Main Results:

• The proposed method effectively mitigates the time walk effect for average photon numbers ranging from 1 to 100.
• Experimental results confirm the method's capability to provide high-precision single-photon detection.
• The technique demonstrates robustness in complex and variable environmental conditions.

Conclusions:

• The adaptive single-photon detection method offers a viable solution for improving laser time transfer accuracy.
• This approach is crucial for advancing applications requiring precise timing over long distances, such as satellite networks.
• The passive compensation mechanism ensures reliable performance without active feedback loops.