Fig. 1. Schematic of the countermeasure against blinding attack for single-photon detectors.

Fig. 2. (Color online) Test environment for the countermeasure against blinding attack.

Fig. 3. (Color online) Test for continuous-wave bright light injection.

Fig. 4. (Color online) Detector response to pulsed blinding attack at different time of the gate. Each curve corresponds to a specific optical pulse intensity ranging from 10⁰ to 10⁵ (in the unit of photons/pulse).

Fig. 5. (Color online) Detector response to different pulse width of blinding attack. (a) Attack using pulse of 1-ns-width. (b) Attack using pulse of 10-ns-width. (c) In-gate attack using pulse of 50-ps-width. (d) Out-of-gate attack using pulse of 50-ps-width.