a sending terminal, configured to generate a quantum optical signal and receive a detection result;

a measurement terminal, comprising:

a beam splitter, configured to generate two measurement optical signals based on the quantum optical signal; and

two single-photon detectors, configured to generate the detection result which is disclosed to the sending terminal and a receiving terminal, wherein the detection result comprises a coincidence count rate, and detection response rates respectively corresponding to different single-photon detectors; and

the receiving terminal, configured to receive the detection result,

wherein the quantum key distribution system further comprises:

at least one polarization controller, provided in the sending terminal, the measurement terminal or the measurement terminal, wherein the at least one polarization controller performs a polarization processing on the quantum optical signal or the detection result using a target transmittance matrix determined based on the detection result, so as to obtain a polarized quantum optical signal or a polarized detection result,

wherein in a case that a polarization controller is provided in the sending terminal, an output terminal of a main component of the sending terminal is connected to the polarization controller; or in a case that a polarization controller is provided in the receiving terminal, an input terminal of a main component of the receiving terminal is connected to the polarization controller; and

wherein the target transmittance matrix is generated by:

obtaining first target parameter values of the polarization controller working under different transmittance matrices in different sub-periods of an i^th period, wherein the different transmittance matrices are determined based on an initial transmittance matrix and preset Jones matrices, and the i^th period comprises several sub-periods; and

generating the target transmittance matrix for an (i+1)^th period based on the first target parameter values.