DEMONSTRATION SIMULATOR OF A QUANTUM KEY DISTRIBUTION SYSTEM Russian patent published in 2023 - IPC H04L9/08 

FIELD: quantum information technologies.

SUBSTANCE: used to demonstrate the basic principles of the quantum key distribution system (QKD), as well as to teach the basics of quantum information technologies using the example of a polarization qubit. The essence of the invention lies in the fact that the demonstration simulator of the quantum key distribution system includes a laser source connected to a laser source controller configured to form individual pulses encoding individual qubits in the quantum key distribution system, change of the duration and energy of the pulses, and also the ability to work in continuous mode with controlled power; a block for preparing a certain state of the polarization qubit, including at least one preparatory phase plate (half-wave) for forming the polarization state of the laser radiation that passes through the said block; a block for measuring the prepared state of the polarization qubit, including along the optical beam: at least one preparatory phase half-wave plate for converting the polarization state of the laser radiation that passes through it, a polarization beam splitter and a pair of photodetectors installed in the output channels of the beam splitter; ADC connected to the detectors of the measurement unit, and a computer connected to the ADC and to the controller of the laser source. The computer contains a data processing unit configured to convert the data coming from the ADC into the number of registered photons, provided that the input radiation is attenuated to a single-photon or quasi-single-photon level. The laser radiation source and detectors are rigidly fixed on the base, the phase plates are made removable with the possibility of changing their rotation angles around their optical axis, and the beam splitter is additionally made movable in the direction perpendicular to the optical path.

EFFECT: providing the possibility of simulating the results of measurements performed in real quantum key distribution systems operating according to various protocols with different input radiation statistics and different parameters of single-photon detectors, based on the readings of real photodetectors that register laser radiation visible to the naked eye.

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