Abstract: A circuit apparatus for calibrating an unequal-arm interferometer, and a quantum communication device are provided. The circuit apparatus includes: a constant-voltage power supply; a heater, provided on a short arm of the unequal-arm interferometer; and a diode, reversely connected between a positive electrode and a negative electrode of output ends of the constant-voltage power supply, and connected in series with the heater, wherein the diode provides a corresponding reverse saturation current to the heater according to a change in ambient temperature, so as to counteract an excess amount of an optical path change on a long arm of the unequal-arm interferometer under the effect of the change in the ambient temperature, relative to an optical path change on the short arm of the unequal-arm interferometer under the effect of the change in the ambient temperature.

Abstract: The gating apparatus comprises: a system synchronization unit configured to acquire a clock of a quantum communication system; and a programmable controller configured to generate at least one periodic gating signal sequence that are synchronized with the clock of the quantum communication system, wherein gating signals in each gating signal sequence are spaced apart from each other by a predetermined duration, such that a single-photon detector can operate in a corresponding Geiger mode for a received optical pulse, and the predetermined duration is an optical path difference between a long arm and a short arm of an unequal-arm interferometer that is used for performing phase encoding in the quantum communication system.

Abstract: The disclosure provides a method and apparatus for extracting an avalanche signal.