Intensity modulation as a preemptive measure against blinding of single-photon detectors based on self-differencing cancellation

TL;DR

This paper investigates how intensity modulation can prevent blinding of self-differencing avalanche photodiodes in quantum key distribution, enhancing security by maintaining detector responsiveness under intense light conditions.

Contribution

It demonstrates experimentally that intensity modulation can counteract detector blinding caused by self-differencing circuitry in high-speed quantum key distribution systems.

Findings

Intensity modulation restores detector response under blinding conditions.

Self-differencing circuitry can be bypassed with proper intensity modulation.

Experimental validation confirms effectiveness of the proposed method.

Abstract

Quantum key distribution is rising as an important cryptographic primitive for protecting the communication infrastructure in the digital era. However, its implementation security is often weakened by components whose behavior deviates from what is expected. Here, we analyse the response of a self-differencing avalanche photodiode, a key enabler for high speed quantum key distribution, to intense light shone from a continuous-wave laser. Under incorrect settings, the cancellation entailed by the self-differencing circuitry can make the detector insensitive to single photons. However, we experimentally demonstrate that even in such cases intensity modulation can be used as an effective measure to restore the detector's expected response to the input light.