in the direction of "Photonics and Optoinformatics", candidate of technical sciences, head of lab. at the Kazan Quantum Center of the KNRTU-KAI. Area of interest: quantum communications, optoelectronics, photonics.

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INTRODUCTIONQuantum networks [1] designed for transferring quantum information to large numbers of users in order to organize safe communication or data exchange between quantum computing machines are now being developed. The typical speeds of quantum bit generation in quantum networks remain relatively slow (no greater than 1-2 Mbit ⋅ s −1 ) [2]. This is mainly due to the low efficiency of detection blocks. Most quantum communication schemes include different kinds of photon detectors for registering quantum states. Photon detectors based on avalanche-type light-emitting diodes are characterized by relatively high levels of dark operations (around 1-10 kHz), and in practical terms have limited registering speeds, due to the need to compensate for the effect of afterpulsing. Superconducting detectors [3] have high quantum efficiency (up to 80% for a wavelength of 1.5 μm), low jitter (100 ps), slow dark counts (around 10 Hz), and are able to determine the number of photons in a count [4]. To ensure their functioning, however, we must cool the sensitive element to temperatures of ~2.5 K. In addition, using devices for counting single photons in quantum communication systems imposes substantial restrictions on their application upon the spectral multiplexing of a quantum channel together with classic information channels.In addition to schemes that use counts of single photons for registering single-photon qubits, there is an alternative approach known as the system of quantum communication on continuous variables, which has been under development for the last decade [5,6]. Here, the quantum states of photon qubits is measured via homodyne detection by mixing the local oscillator field with signal radiation, which carries information about the state of photon qubits. An advantage of this approach is high count speed and the simple design of the detector.The authors of [7] proposed the scheme of quantum communication on side frequencies (QCSF). A distinguishing feature of the QCSF system compared to other schemes is its way of generating and encoding single-photon states. Single photons are not irradiated directly by a source, but are carried to the side frequencies of spectrum as a result of phase modulation by the radio frequency signal of intense singlefrequency laser irradiation. At the same time, the phase of the modulating signal determines the phase shift between radiation on the central and side frequencies, allowing us to implement protocols of quantum communication B92 [8], BB84 [9], and so on. Due to the selected shape of the optical signal scheme, QCSF has considerable advantages in creating quantum networks based on the existing infrastructure of optical communication. These include stability against the effects external conditions have on the parameters of signal photons, unidirectionality of the optical scheme, and higher spectral efficiency [10].This work proposes an optical scheme QCSF with heterodyne signal detection, which in the future will allow us to build a protocol of quantum communication on ...

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