RU2784025C1 - Device for quantum sending of a cryptographic key with frequency coding - Google Patents

Abstract

FIELD: cryptographic technique.

SUBSTANCE: invention relates to cryptographic technique, namely to systems of quantum distribution of a cryptographic key. A device for quantum distribution of a cryptographic key with frequency coding is proposed. The device comprises a transmitting device and a receiving device connected to each other by a fiber-optic communication line. The transmitting device contains a source of monochromatic radiation, the output of which is optically coupled to the input of the electro-optical amplitude modulator of the transmitting device, the control input of the electro-optical amplitude modulator of the transmitting device is connected to the output of the phase shifter of the transmitting device. The receiving device also contains a spectral filter, the first output of which is optically coupled to the input of the classical radiation receiver, the output of the classical radiation receiver is the first output of the frequency-coded cryptographic key quantum distribution device.

EFFECT: increasing the protection of the quantum cryptographic key, due to several modes of operation of the device, namely the mode of active detection of the state of photons and the mode of passive detection of the state of photons.

1 cl, 20 dwg

Description

SUBSTANCE: invention relates to cryptographic technique, namely to systems of quantum distribution of a cryptographic key.

A device for quantum distribution of a cryptographic key on a subcarrier frequency of modulated radiation is known [RF Patent RU2454810 (C1), publication date 2012-06-27., priority date 24.11.2010. MKI: H04L 9/08], containing, connected via a fiber-optic communication line, a transmitting device, including a monochromatic radiation source located in series along the radiation path, an electro-optical phase modulator and an attenuator, as well as a phase shift device, the output of which is connected to the control input of the electro-optical phase modulator, and the input of the phase shifter is connected to the output of the RF signal generator, and the receiving device, including an electro-optical phase modulator, a classical radiation receiver, optically coupled with a spectral filter and a single photon receiver, the electro-optical phase modulator is connected to the phase shifter, to the input of which the output of the RF signal generator is connected, the fiber-optic communication line is optically coupled to the attenuator of the transmitting device, the device contains a synchronization unit, the first and second outputs of which are connected to the inputs of the RF signal generator and the receiving and transmitting devices, respectively, moreover, the electro-optical phase modulator in the receiving device is made of two electro-optical phase modulators located along the radiation direction, the control inputs of which are connected to the first and second outputs of the phase shift device, respectively, and the output of the first electro-optical phase modulator is optically coupled to the output of the second an electro-optical phase modulator, a Faraday mirror is installed behind the modulators along the radiation path, optically coupled to the input of the second electro-optical phase modulator, an optical circulator is introduced into the receiving device, the first port of which is optically coupled to the fiber-optic communication line, the second port is optically coupled to the input of the first electro-optical phase modulator modulator, the third port is optically coupled to the spectral filter, and the fourth port is optically coupled to the input of the single photon receiver, the synchronization device has the third and fourth outputs, which rye are connected to the synchronization inputs of the phase shifters of the receiving and transmitting devices, respectively.

The prototype for the proposed device for quantum distribution of a cryptographic key with frequency coding is a device for quantum distribution of a cryptographic key with frequency coding [RF Patent RU2692431 (C1), publication date 2019-06-24, priority date 03.07.2018. MKI: H04L 9/08, H04B 10/85], containing, interconnected by a fiber-optic communication line, the transmitter and receiver; as well as a synchronization unit; while the transmitter includes a source of monochromatic radiation, an electro-optical phase modulator of the transmitter, the output of which is optically coupled to the input of the attenuator, the output of the attenuator is optically coupled to the input of the fiber-optic communication line; as well as a device for shifting the phase of the transmitter, the input of which is connected to the first output of the RF signal generator of the transmitter; wherein the receiving device includes an electro-optical phase modulator of the receiving device, an optical circulator, the second port of the optical circulator is optically coupled to the input of the spectral filter, the third port of the optical circulator is optically coupled to the input of the single photon receiver, the output of the single photon receiver is the first output of the quantum spreading device frequency-coded cryptographic key, the output of the spectral filter is optically coupled to the input of the classical radiation receiver, the output of the classical radiation receiver is the second output of the frequency-coded cryptographic key quantum distribution device, as well as the phase shift device of the receiving device, the input of the receiver phase shift device is connected to the first the output of the radio frequency signal generator of the receiving device; wherein the first and second outputs of the synchronization unit are connected to the synchronization inputs of the RF signal generator of the transmitter and the RF signal generator of the receiver, respectively, the third and fourth outputs of the synchronization unit are connected to the synchronization inputs of the phase shift device of the transmitter and the phase shift device of the receiver, respectively, and in The transmitting device additionally includes an electro-optical amplitude modulator of the transmitting device and a radio-frequency signal converter of the transmitting device, wherein the input of the electro-optical amplitude modulator of the transmitting device is optically coupled to the output of the monochromatic radiation source, the output of the electro-optical amplitude modulator of the transmitting device is optically coupled to the input of the electro-optical phase modulator of the transmitting device, and the control input of the electro-optical amplitude modulator of the transmitting device is connected to the output of the transmitter phase shifter, the input of the RF signal converter of the transmitter is connected to the second output of the RF signal generator of the transmitter, and the output of the RF signal converter of the transmitter is connected to the control input of the electro-optical phase modulator of the transmitter; an electro-optical amplitude modulator of the receiving device, a radio-frequency signal converter of the receiving device are also additionally introduced into the receiving device, while the input of the electro-optical amplitude modulator of the receiving device is optically coupled to the output of the electro-optical phase modulator of the receiving device, the output of the electro-optical amplitude modulator of the receiving device is optically coupled to the first port of the optical circulator, the control input of the electro-optical amplitude modulator of the receiving device is connected to the output of the phase shift device of the receiving device, the input of the radio frequency signal converter of the receiving device is connected to the second output of the radio frequency signal generator of the receiving device, the output of the radio frequency signal converter of the receiving device is connected to the control input of the electro-optical phase modulator of the receiving device, the input of the electro-optical phase modulator receiver optically coupled with the output of the fiber-optic communication line.

The technical solution of the prototype has only one mode of operation of the device, the mode of active detection of the state of photons, which provides only one level of cryptographic protection, which is not enough to protect the quantum cryptographic key.

The technical problem is the creation of a device for quantum distribution of a cryptographic key with frequency coding, which makes it possible to increase the protection of a quantum cryptographic key, due to several modes of operation of the device, namely the mode of active detection of the state of photons and the mode of passive detection of the state of photons, which will provide several levels of cryptographic protection.

The technical result of the invention is to increase the security of a quantum cryptographic key, due to several modes of operation of the device, namely the mode of active detection of the state of photons and the mode of passive detection of the state of photons.

The technical result in a device for quantum distribution of a cryptographic key with frequency coding, containing a transmitting device and a receiving device connected to each other by a fiber-optic communication line; wherein the transmitter contains a source of monochromatic radiation, the output of which is optically coupled to the input of the electro-optical amplitude modulator of the transmitter, the control input of the electro-optical amplitude modulator of the transmitter is connected to the output of the phase shifter of the transmitter, the output of the electro-optical amplitude modulator of the transmitter is optically coupled to the input of the electro-optical phase modulator of the transmitting device, the control input of the electro-optical phase modulator of the transmitting device is connected to the output of the radio frequency signal converter of the transmitting device, the output of the electro-optical phase modulator of the transmitting device is optically coupled to the input of the attenuator, the output of the attenuator is optically coupled to the input of the fiber-optic communication line, the transmitting device also contains a radio frequency signal generator transmitting device, the first output of which is connected to the input of the device with phase shift of the transmitting device; wherein the receiving device includes an electro-optical phase modulator of the receiving device, the input of which is optically coupled to the output of the fiber-optic communication line, the control input of the electro-optical phase modulator of the receiving device is connected to the output of the RF signal converter of the receiving device, the output of the electro-optical phase modulator of the receiving device is optically coupled with the input of the electro-optical amplitude modulator of the receiving device, the control input of the electro-optical amplitude modulator of the receiving device is connected to the output of the phase shifter of the receiving device, the input of the phase shifter of the receiving device is connected to the first output of the radio frequency signal generator of the receiving device, the receiving device also contains a spectral filter, the first output of which optically coupled to the input of the classical radiation receiver, the output of the classical radiation receiver is the first output of the quantum frequency-coded cryptographic key distribution, the receiving device also contains the first single photon receiver, the output of which is the second output of the frequency-coded cryptographic key quantum distribution device, while the first and second outputs of the synchronization unit are connected to the synchronization inputs of the radio frequency signal generator of the transmitting device and the radio frequency generator. signal of the receiving device, respectively, the third and fourth outputs of the synchronization unit are connected to the synchronization inputs of the phase shift device of the transmitting device and the phase shift device of the receiving device, respectively, is achieved by the fact that a device for adjusting the phase of the transmitting device is additionally introduced into the transmitting device, the output of which is connected to the input of the radio frequency converter signal of the transmitting device, the input of the phase adjustment device of the transmitting device is connected to the second output of the RF signal generator p transmitting device; at the same time, a device for adjusting the phase of the receiving device is also additionally introduced into the receiving device, the output of which is connected to the input of the radio frequency signal converter of the receiving device, the input of the phase adjusting device of the receiving device is connected to the second output of the generator of the radio frequency signal of the transmitting device, in the receiving device the spectral filter is multichannel and has five outputs, the input of the spectral filter is optically coupled to the output of the electro-optical amplitude modulator of the receiving device, the second output of the spectral filter is optically coupled to the input of the first single photon receiver, the second single photon receiver is additionally introduced into the receiving device, the output of which is the third output of the cryptographic key quantum distribution device frequency-coded, the input of the second single photon receiver is optically coupled to the third output of the spectral filter, the third single photon receiver, the output of which o is the fourth output of the frequency-coded cryptographic key quantum distribution device, the input of the third single photon receiver is optically coupled to the fourth output of the spectral filter, the fourth single photon receiver, the output of which is the fifth output of the frequency-coded cryptographic key quantum distribution device, the input of the fourth single photon receiver optically coupled to the fifth spectral filter output; as well as the synchronization unit has the fifth and sixth outputs, while the fifth and sixth outputs of the synchronization unit are connected to the synchronization inputs of the transmitter phase adjustment device and the receiver phase adjustment device, respectively.

The invention is illustrated by drawings, where figure 1 shows a diagram of a device for quantum distribution of a cryptographic key with frequency coding. Figure 2 - the frequency spectrum of the original signal at the output of the source of monochromatic radiation. Figure 3 - the frequency spectrum of the amplitude-modulated signal at the output of the electro-optical amplitude modulator of the transmitter. Figure 4 - the frequency spectrum of the phase-switched signal at the output of the electro-optical phase modulator of the transmitter. Figure 5 - the frequency spectrum of the rephase-switched signal at the output of the electro-optical phase modulator of the receiving device. In Fig.6 - the frequency spectrum of the amplitude-remodulated signal in the case, at the output of the electro-optical amplitude modulator of the receiving device, when the phase difference of the two modulating signals is 0. In Fig.7 - the frequency spectrum of the amplitude-remodulated signal in the case, at the output of the electro-optical amplitude modulator receiving device when the phase difference of the two modulating signals is equal to π. In Fig.8 - the frequency spectrum of the carrier frequency arriving at the receiver of classical radiation. Figure 9 - the frequency spectrum of the signal arriving at the receiver of single photons. Figure 10 - the frequency spectrum of the original signal at the output of the source of monochromatic radiation. In Fig.11 - the frequency spectrum of a two-frequency amplitude-modulated signal at a frequency Ω, at the output of the electro-optical amplitude modulator of the transmitter. On Fig.12 - the frequency spectrum of a single-photon two-frequency amplitude-modulated signal at a frequency Ω, at the output of the attenuator. In Fig.13 - the frequency spectrum of the amplitude-modulated signal at a frequency Ω, at the output of the electro-optical amplitude modulator of the transmitter. In Fig.14 - the frequency spectrum of the phase-switched signal at a frequency of Ω/2, at the output of the electro-optical phase modulator of the transmitter. In Fig.15 - the frequency spectrum of a single-photon phase-switched signal at a frequency of Ω / 2, at the output of the attenuator. In Fig.16 - the frequency spectrum of the amplitude-modulated signal at a frequency Ω, at the output of the electro-optical amplitude modulator of the transmitter. On Fig.17 - the frequency spectrum of the phase-switched signal at a frequency of 3Ω/2, at the output of the electro-optical phase modulator of the transmitter. In Fig.18 - the frequency spectrum of a single-photon phase-switched signal at a frequency of Ω / 2, at the output of the attenuator. In Fig.19 - the frequency spectrum of a two-frequency amplitude-modulated signal at a frequency of 2Ω, at the output of the electro-optical amplitude modulator of the transmitter. On Fig.20 - the frequency spectrum of a single-photon two-frequency amplitude-modulated signal at a frequency of 2Ω, at the output of the attenuator.

The inventive device for quantum distribution of a cryptographic key with frequency coding, shown in Fig.1, contains connected to each other by a fiber-optic communication line 1, a transmitter 2 and a receiver 3, as well as a synchronization unit 4; while the transmitter 2 includes: optically coupled in series, a source of monochromatic radiation 5, an electro-optical amplitude modulator of the transmitter 6, an electro-optical phase modulator of the transmitter 7 and an attenuator 8, the output of the attenuator 8 is the output of the transmitter 2 and is optically coupled to the input of the fiber of the optical communication line 1, as well as the phase shifter of the transmitter 9, the input of the phase shifter of the transmitter 9 is connected to the first output of the RF signal generator of the transmitter 10, and the output of the phase shifter of the transmitter 9 is connected to the control input of the electro-optical amplitude modulator of the transmitter 6 , the second output of the RF signal generator of the transmitter 10 is connected to the input of the phase adjustment device of the transmitter 11, the output of the phase adjustment device of the transmitter 11 is connected to the input of the radio frequency converter signal of the transmitter 12, the output of the RF signal converter of the transmitter 12 is connected to the control input of the electro-optical phase modulator of the transmitter 7, the first and second outputs of the RF signal generator of the transmitter 10 are identical to each other; while the receiver 3 includes: sequentially optically coupled, an electro-optical phase modulator of the receiver 13, an electro-optical amplitude modulator of the receiver 14, the spectral filter 15 is multichannel and has five outputs, the first output of the spectral filter 15 is optically coupled to the input of the classical radiation receiver 16 , the output of the classical radiation receiver 16 is the first output of the frequency-coded cryptographic key quantum distribution device, the second output of the spectral filter 15 is optically coupled to the input of the first single photon receiver 17, the output of the first single-photon receiver 17 is the second output of the frequency-coded cryptographic key quantum distribution device , the third output of the spectral filter 15 is optically coupled to the input of the second single photon receiver 18, the output of the second single photon receiver 18 is the third output of the CREE quantum ptographic key with frequency coding, the fourth output of the spectral filter 15 is optically coupled to the input of the third receiver of single photons 19, the output of the third receiver of single photons 19 is the fourth output of the quantum distribution device of the cryptographic key with frequency coding, the fifth output of the spectral filter 15 is optically coupled to the input of the fourth receiver single photons 20, the output of the fourth receiver of single photons 20 is the fifth output of the quantum distribution device of the cryptographic key with frequency coding, while the input of the electro-optical phase modulator of the receiving device 13 is the input of the receiving device 3 and is optically coupled to the output of the fiber optic communication line 1, the receiving device 3 also includes, a phase shifter of the receiver 21, an input of the phase shifter of the receiver 21 is connected to the first output of the RF signal generator of the receiver 22, and the output of the receiver The phase shifting device of the receiving device 21 is connected to the control input of the electro-optical amplitude modulator of the receiving device 14, the second output of the RF signal generator of the receiving device 22 is connected to the input of the phase adjustment device of the receiving device 23, the output of the phase adjustment device of the receiving device 23 is connected to the input of the RF signal converter of the receiving device 24, the output of the RF signal converter of the receiver 24 is connected to the control input of the electro-optical phase modulator of the receiver 14, the first and second outputs of the RF signal generator of the receiver 22 are identical to each other; wherein the first and second outputs of the synchronization unit 4 are connected to the synchronization inputs of the RF signal generator of the transmitter 10 and the RF signal generator of the receiver 22, respectively, the third and fourth outputs of the synchronization unit 4 are connected to the synchronization inputs of the phase shift device of the transmitter 9 and the phase shift device of the receiving device device 21, respectively, the fifth and sixth outputs of the synchronization unit 4 are connected to the synchronization inputs of the phase adjustment device of the transmitter 11 and the phase adjustment device of the receiving device 23, respectively, while the elements that make up the transmitter 2, the source of monochromatic radiation 5, the attenuator 8, the device transmitter phase shifter 9, transmitter RF signal generator 10, transmitter phase adjuster 11, transmitter RF signal converter 12, and input elements consisting of a receiver 3, a classical radiation receiver 16, a first single photon receiver 17, a second single photon receiver 18, a third single photon receiver 19, a fourth single photon receiver 20, a phase shifter of the receiver 21, an RF signal generator of the receiver 22, the phase adjustment device of the receiving device 23, the RF signal converter of the receiving device 24, and the synchronization unit 4 have a power supply system, which is not shown in the diagram.

Let us consider the device for quantum distribution of a cryptographic key with frequency coding shown in Fig.1 in the mode of active detection of the state of photons, i.e. with remodulation in the receiver. The power supply system is preliminarily turned on and voltage is applied to the elements included in the transmitter 2, the source of monochromatic radiation 5, the attenuator 8, the phase shift device of the transmitter 9, the RF signal generator of the transmitter 10, the device for adjusting the phase of the transmitter 11, the RF signal converter of the transmitter 12, and on the elements included in the receiver 3, the classical radiation receiver 16, the first single photon receiver 17, the second single photon receiver 18, the third single photon receiver 19, the fourth single photon receiver 20, the phase shift device of the receiving device 21, the RF generator signal of the receiving device 22, the device for adjusting the phase of the receiving device 23, the radio frequency signal converter of the receiving device 24, and the synchronization unit 4. On the transmitting device 2, the source of monochromatic radiation 5 generates light th beam with frequency ω ₀ (figure 2). The radiation is subjected to amplitude modulation in the electro-optical amplitude modulator of the transmitter 6. In the simplest case, periodic sinusoidal modulation is used. The source of the sinusoidal signal is the RF signal generator of the transmitter 10. As a result of amplitude modulation, two side frequencies ω ₀ - Ω _a and ω ₀ + Ω _a appear in the signal spectrum (Fig. 3), which are separated from the main frequency of the optical signal ω ₀ by the frequency value Ω _a (Fig. 3) (Ω _a is the frequency of the modulating RF signal for amplitude modulation). Further, the amplitude-modulated signal undergoes phase switching in the electro-optical phase modulator of the transmitter 7, such a rectangular phase modulation is applied in which the modulation phase is reversed by 180 degrees with each passage of the zero point of the sinusoidal modulation, as a result of which all the energy of the carrier frequency is pumped into the side components ω ₀ – Ω _f and ω ₀ + Ω _f (Fig.4) (Ω _f is the frequency of the modulating radio frequency signal for phase modulation), thus, the multiphoton carrier frequency is excluded from the quantum transmission channel. The source of the square wave signal is the RF signal converter of the transmitter 12. The phase adjustment of the square wave, in order to obtain ideal carrier suppression in the signal structure, is carried out in the phase adjuster of the transmitter 11. Next, the light beam is attenuated to a single-photon level using an attenuator 8. the time between two generated photons in one pulse was longer than the transmission time of one bit of information. This condition is ensured by changing the modulation index, namely, by adjusting the amplitude of the modulating signal, which is carried out in the RF signal generator of the transmitter 10 and the RF signal generator of the receiver 22. The information bit is encoded by introducing some phase shift Ф _А into the modulating signal (Ф _А - phase shift input in the transmitter 2). The phase shift is controlled by the phase shift device of the transmitting device 9. The transmitting device 2 is connected to the receiving device 3 by a fiber optic communication line 1, which is a quantum channel.

The phase-switched signal (Fig.4) is transmitted to the receiver 3, where it is subjected to repeated phase switching (rephase switching) in the electro-optical phase modulator of the receiver 13 to recover from the side components ω ₀ - Ω _f and ω ₀ + Ω _f (Fig. .4) carrier frequency ω ₀ (Fig.5) for further repeated amplitude modulation (remodulation) in the electro-optical amplitude modulator of the receiving device 14. The receiving device uses its own radio frequency signal converter of the receiving device 24, the device for adjusting the phase of the receiving device 23, the RF signal generator receiving device 22 and the phase shifter of the receiving device 21, the functions of which are identical to those used in the transmitting device 2. A certain phase shift FB is also introduced into the amplitude _modulating signal ( _FB is the phase shift introduced in the receiving device 3), the device phase shift of the receiving device 21. Radiation intensity per subcarrier frequency x ω ₀ - Ω _a and ω ₀ + Ω _a (Fig.6), depends on the phase shift values entered on the phase shift device of the transmitter 9 (F _A ) and on the phase shift device of the receiving device 21 (F _B ). In the case when the modulating radio frequency signals of the transmitter 2 and the receiver 3 are in-phase ΔF=0, i.e. the phase difference of the two modulating RF signals is equal to zero (F _A -F _B =0), at subcarrier frequencies ω ₀ - Ω _a and ω ₀ + Ω _a (Fig.6) there is constructive interference, and the intensity of the optical signal is maximum. In the case when the modulating radio frequency signals of the transmitter 2 and the receiver 3 are in antiphase ΔФ=π, i.е. the phase difference of the modulating signals is equal to π (F _A -F _B = π), destructive interference is observed, and the signal intensity at subcarrier frequencies ω ₀ - Ω _a and ω ₀ + Ω _a (Fig. 7) is actually equal to zero.

From the electro-optical amplitude modulator of the receiving device 14, the signal enters the input of the spectral filter 15. In the spectral filter 15, the spectral components of the signal are separated. The signal at the carrier frequency ω ₀ (Fig.8), which is the reference signal, passes through the first output of the spectral filter 15 and enters the classical radiation receiver 16. Signals at subcarrier frequencies ω ₀ - Ω _a and ω ₀ + Ω _a (Fig. 9 ) passes through the second output of the spectral filter 15 and enters the first single photon receiver 17.

Signals at the fundamental frequency ω ₀ (Fig.8) and subcarrier frequencies ω ₀ - Ω _a and ω ₀ + Ω _a (Fig. 9) are detected separately. The signal at the fundamental frequency ω ₀ (Fig.8) is a reference signal and is detected by the classical radiation receiver 16. Its detection is necessary to confirm the presence of the transmitted information bit. The signal at subcarrier frequencies ω ₀ - Ω _a and ω ₀ + Ω _a (Fig. 9) is recorded by the first single photon receiver 17. The data received from the classical radiation receiver 16 and from the first single photon receiver 17 are transmitted through the first and second, respectively. the output of the device for quantum distribution of a cryptographic key with frequency coding to a computer (which is not shown in the diagram), and further processing of this data is performed on a computer. Analyzing signals at subcarrier frequencies ω ₀ - Ω _a and ω ₀ + Ω _a (Fig.9) of optical radiation, the intensity of which depends on the phase difference F _A and F _B of the two modulating signals, the transmitting device and the receiving device receive a secret cryptographic key and make conclusion about the presence of an eavesdropping intruder.

The synchronization unit 4 ensures the stability of the frequency of the modulating radio frequency signals of the transmitter 2 and the receiver 3, and also controls the clock frequency of the sequence of phase shift values on the phase shift device of the transmitter 9, on the phase adjuster of the transmitter 11, on the phase shift device of the receiver 21 and on the device for adjusting the phase of the receiving device 23.

Let us consider the device for quantum distribution of a cryptographic key with frequency coding shown in Fig.1 in the mode of operation of passive detection of the state of photons, i.e. without remodulation at the receiver. The power supply system is preliminarily turned on and voltage is applied to the elements that make up the transmitter 2, the source of monochromatic radiation 5, the attenuator 8, the phase shift device of the transmitter 9, the RF signal generator of the transmitter 10, the device for adjusting the phase of the transmitter 11, the converter of the radio frequency signal of the transmitter device 12, and elements included in the receiver 3, classical radiation receiver 16, the first single photon receiver 17, the second single photon receiver 18, the third single photon receiver 19, the fourth single photon receiver 20.

, на передающем устройстве 2, источником монохроматического излучения 5 генерируется световой пучок с частотой ω₀ (фиг.10). Дальше излучение подвергается амплитудной модуляции в электрооптическом амплитудном модуляторе передающего устройства 6. В данном случае применяется амплитудная модуляция, напряжением с частотой Ω в «нулевой» рабочей точке амплитудного модулятора передающего устройства 6. Источником синусоидального сигнала является генератор радиочастотного сигнала передающего устройства 10. В результате амплитудной модуляции на выходе электрооптического амплитудного модулятора передающего устройства 6 появляется двухчастотное излучение на частотах ω₀ – Ω и ω₀ + Ω (фиг.11), (Ω – частота модулирующего радиочастотного сигнала для амплитудной модуляции). Далее амплитудно-модулированный излучение (фиг.11), проходит через открытый электрооптический фазовый модулятор передающего устройства 7 без модуляции. Далее двухчастотное излучение (фиг.11) ослабляется до однофотонного уровня с помощью аттенюатора 8 (фиг.12). Полученный на выходе аттенюатора 8 однофотонное двухчастотное излучение на частотах ω₀ – Ω и ω₀ + Ω (фиг.12), передается на приемное устройство 3 через волоконно-оптическую линию связи 1, которая представляющей собой квантовый канал, который соединяет передающее устройство 2 с приемным устройством 3. Однофотонное двухчастотное излучение на частотах ω₀ – Ω и ω₀ + Ω (фиг.12) в приемном устройстве 3 попадает на вход спектрального фильтра 15, где разделяются спектральные составляющие излучения. Однофотонное двухчастотное излучение на частотах ω₀ – Ω и ω₀ + Ω (фиг.12) выходит через второй выход спектрального фильтра 15 и попадает на вход первого приемника одиночных фотонов 17, где детектируется факт приема фотона.To transmit the first of the four orthogonal states of the photon, the state

, on the transmitter 2, the source of monochromatic radiation 5 generates a light beam with a frequency ω₀(Fig.10). Further, the radiation is subjected to amplitude modulation in the electro-optical amplitude modulator of the transmitting device 6. In this case, amplitude modulation is applied, with a voltage with a frequency Ω at the "zero" operating point of the amplitude modulator of the transmitting device 6. The source of the sinusoidal signal is the RF signal generator of the transmitting device 10. As a result of the amplitude modulation at the output of the electro-optical amplitude modulator of the transmitter 6, two-frequency radiation appears at frequencies ω₀– Ω and ω₀+Ω (Fig.11), (Ω is the frequency of the modulating RF signal for amplitude modulation). Next, amplitude-modulated radiation (Fig.11) passes through an open electro-optical phase modulator of the transmitter 7 without modulation. Next, the two-frequency radiation (Fig.11) is attenuated to a single-photon level using the attenuator 8 (Fig.12). Received at the output of the attenuator 8 single-photon two-frequency radiation at frequencies ω₀– Ω and ω₀+Ω (Fig.12) is transmitted to the receiver 3 through a fiber-optic communication line 1, which is a quantum channel that connects the transmitter 2 to the receiver 3. Single-photon dual-frequency radiation at frequencies ω₀– Ω and ω₀+Ω (Fig.12) in the receiving device 3 enters the input of the spectral filter 15, where the spectral components of the radiation are separated. Single-photon two-frequency radiation at frequencies ω₀– Ω and ω₀+Ω (Fig.12) exits through the second output of the spectral filter 15 and enters the input of the first receiver of single photons 17, where the fact of receiving a photon is detected.

, на передающем устройстве 2, источником монохроматического излучения 5 генерируется световой пучок с частотой ω₀ (фиг.10). Дальше излучение подвергается амплитудной модуляции в электрооптическом амплитудном модуляторе передающего устройства 6. В данном случае применяется амплитудная модуляция при работе электрооптического амплитудного модулятора передающего устройства 6 на линейном участке напряжением с частотой Ω и коэффициентом амплитудной модуляции m=0,55. Источником синусоидального сигнала является генератор радиочастотного сигнала передающего устройства 10. В результате амплитудной модуляции на выходе электрооптического амплитудного модулятора передающего устройства 6 появляется излучение в спектре которого формируются две боковые частоты ω₀ – Ω и ω₀ + Ω (фиг.13), отстоящие от основной частоты оптического сигнала ω₀ на величину частоты Ω (фиг.13) (Ω – частота модулирующего радиочастотного сигнала для амплитудной модуляции). Далее амплитудно-модулированное излучение проходит фазовую коммутацию в электрооптическом фазовом модуляторе передающего устройства 7, применяется такая прямоугольная фазовая модуляция, при которой фаза модуляции переворачивается на 180 градусов при каждом прохождении нулевой точки синусоидальной модуляции, вследствие чего вся энергия несущей частоты перекачивается в боковые составляющие ω₀ – Ω/2 и ω₀ + Ω/2 (фиг.14) (Ω/2 – частота модулирующего радиочастотного сигнала для фазовой модуляции, где – Ω равно частоте модулирующего радиочастотного сигнала для амплитудной модуляции), в результате которого, появляется двухчастотное излучение на частотах ω₀ – Ω/2 и ω₀ + Ω/2 (фиг.14). тем самым, из квантового канала передачи исключается многофотонная несущая частота. Источником прямоугольного сигнала является преобразователь радиочастотного сигнала передающего устройства 12. Подстройка фазы прямоугольного сигнала, для получения идеального подавления несущей в структуре сигнала, осуществляется в устройстве подстройки фазы передающего устройства 11. Далее двухчастотное излучение на частотах ω₀ – Ω/2 и ω₀ + Ω/2 (фиг.14) ослабляется до однофотонного уровня с помощью аттенюатора 8 (фиг.15). Полученный на выходе аттенюатора 8 однофотонное двухчастотное излучение на частотах ω₀ – Ω/2 и ω₀ + Ω/2 (фиг.15), передается на приемное устройство 3 через волоконно-оптическую линию связи 1, которая представляющей собой квантовый канал, который соединяет передающее устройство 2 с приемным устройством 3. Однофотонное двухчастотное излучение на частотах ω₀ – Ω/2 и ω₀ + Ω/2 (фиг.15) в приемном устройстве 3 попадает на вход спектрального фильтра 15, где разделяются спектральные составляющие излучения. Однофотонное двухчастотное излучение на частотах ω₀ – Ω/2 и ω₀ + Ω/2 (фиг.15) выходит через третий выход спектрального фильтра 15 и попадает на вход второго приемника одиночных фотонов 18, где детектируется факт приема фотона.To transmit the second of the four orthogonal states of the photon, the states

, on the transmitter 2, the source of monochromatic radiation 5 generates a light beam with a frequency ω₀(Fig.10). Further, the radiation is subjected to amplitude modulation in the electro-optical amplitude modulator of the transmitting device 6. In this case, amplitude modulation is applied when the electro-optical amplitude modulator of the transmitting device 6 is operating in a linear section with a voltage with a frequency Ω and an amplitude modulation coefficientm=0.55. The source of the sinusoidal signal is the radio frequency signal generator of the transmitter 10. As a result of amplitude modulation, at the output of the electro-optical amplitude modulator of the transmitter 6, radiation appears in the spectrum of which two side frequencies ω are formed₀ – Ω and ω₀ + Ω (Fig.13), separated from the main frequency of the optical signal ω₀ by the value of the frequency Ω (Fig.13) (Ω is the frequency of the modulating RF signal for amplitude modulation). Further, the amplitude-modulated radiation undergoes phase switching in the electro-optical phase modulator of the transmitter 7, such a rectangular phase modulation is applied in which the modulation phase is reversed by 180 degrees with each passage of the zero point of the sinusoidal modulation, as a result of which all the energy of the carrier frequency is pumped into the side components ω₀– Ω/2 and ω₀+ Ω/2 (Fig.14) (Ω/2 is the frequency of the modulating radio frequency signal for phase modulation, where – Ω is equal to the frequency of the modulating radio frequency signal for amplitude modulation), as a result of which two-frequency radiation appears at frequencies ω₀– Ω/2 and ω₀+ Ω/2 (Fig. 14). thus, the multiphoton carrier frequency is excluded from the quantum transmission channel. The source of the square wave signal is the radio frequency signal converter of the transmitter 12. The phase adjustment of the square wave, in order to obtain ideal carrier suppression in the signal structure, is carried out in the phase adjustment device of the transmitter 11. Further, two-frequency radiation at frequencies ω₀– Ω/2 and ω₀+ Ω/2 (Fig.14) is attenuated to a single-photon level using attenuator 8 (Fig.15). Received at the output of the attenuator 8 single-photon two-frequency radiation at frequencies ω₀– Ω/2 and ω₀+ Ω/2 (Fig.15) is transmitted to the receiving device 3 through a fiber-optic communication line 1, which is a quantum channel that connects the transmitting device 2 to the receiving device 3. Single-photon dual-frequency radiation at frequencies ω₀– Ω/2 and ω₀+ Ω/2 (Fig.15) in the receiver 3 enters the input of the spectral filter 15, where the spectral components of the radiation are separated. Single-photon two-frequency radiation at frequencies ω₀– Ω/2 and ω₀+ Ω/2 (Fig.15) goes through the third output of the spectral filter 15 and enters the input of the second receiver of single photons 18, where the fact of receiving a photon is detected.

, на передающем устройстве 2, источником монохроматического излучения 5 генерируется световой пучок с частотой ω₀ (фиг.10). Дальше излучение подвергается амплитудной модуляции в электрооптическом амплитудном модуляторе передающего устройства 6. В данном случае применяется амплитудная модуляция при работе электрооптического амплитудного модулятора передающего устройства 6 на линейном участке напряжением с частотой

и коэффициентом амплитудной модуляции m=0,55. Источником синусоидального сигнала является генератор радиочастотного сигнала передающего устройства 10. В результате амплитудной модуляции на выходе электрооптического амплитудного модулятора передающего устройства 6 появляется излучение в спектре которого формируются две боковые частоты ω₀ – Ω и ω₀ + Ω (фиг.16), отстоящие от основной частоты оптического сигнала ω₀ на величину частоты Ω (фиг.16) (Ω – частота модулирующего радиочастотного сигнала для амплитудной модуляции). Далее амплитудно-модулированное излучение проходит фазовую коммутацию в электрооптическом фазовом модуляторе передающего устройства 7, применяется такая прямоугольная фазовая модуляция, при которой фаза модуляции переворачивается на 180 градусов при каждом прохождении нулевой точки синусоидальной модуляции, вследствие чего вся энергия несущей частоты перекачивается в боковые составляющие ω₀ – 3Ω/2 и ω₀ + 3Ω/2 (фиг.17) (3Ω/2 – частота модулирующего радиочастотного сигнала для фазовой модуляции, где – Ω равно частоте модулирующего радиочастотного сигнала для амплитудной модуляции), в результате которого, появляется двухчастотное излучение на частотах ω₀ – 3Ω/2 и ω₀ + 3Ω/2 (фиг.17), тем самым, из квантового канала передачи исключается многофотонная несущая частота. Источником прямоугольного сигнала является преобразователь радиочастотного сигнала передающего устройства 12. Подстройка фазы прямоугольного сигнала, для получения идеального подавления несущей в структуре сигнала, осуществляется в устройстве подстройки фазы передающего устройства 11. Далее двухчастотное излучение на частотах ω₀ – 3Ω/2 и ω₀ + 3Ω/2 (фиг.17) ослабляется до однофотонного уровня с помощью аттенюатора 8 (фиг.18). Полученный на выходе аттенюатора 8 однофотонное двухчастотное излучение на частотах ω₀ – 3Ω/2 и ω₀ + 3Ω/2 (фиг.18), передается на приемное устройство 3 через волоконно-оптическую линию связи 1, которая представляющей собой квантовый канал, который соединяет передающее устройство 2 с приемным устройством 3. Однофотонное двухчастотное излучение на частотах ω₀ – 3Ω/2 и ω₀ + 3Ω/2 (фиг.18) в приемном устройстве 3 попадает на вход спектрального фильтра 15, где разделяются спектральные составляющие излучения. Однофотонное двухчастотное излучение на частотах ω₀ – 3Ω/2 и ω₀ + 3Ω/2 (фиг.18) выходит через четвертый выход спектрального фильтра 15 и попадает на вход третьего приемника одиночных фотонов 19, где детектируется факт приема фотона.To transmit the third of the four orthogonal states of the photon, the state

, on the transmitter 2, the source of monochromatic radiation 5 generates a light beam with a frequency ω₀(Fig.10). Further, the radiation is subjected to amplitude modulation in the electro-optical amplitude modulator of the transmitting device 6. In this case, amplitude modulation is applied when the electro-optical amplitude modulator of the transmitting device 6 is operating in a linear section with a voltage with a frequency

and amplitude modulation factorm=0.55. The source of the sinusoidal signal is the radio frequency signal generator of the transmitter 10. As a result of amplitude modulation, at the output of the electro-optical amplitude modulator of the transmitter 6, radiation appears in the spectrum of which two side frequencies ω are formed₀ – Ω and ω₀ + Ω (Fig.16), spaced from the main frequency of the optical signal ω₀ by the value of the frequency Ω (Fig.16) (Ω is the frequency of the modulating RF signal for amplitude modulation). Further, the amplitude-modulated radiation undergoes phase switching in the electro-optical phase modulator of the transmitter 7, such a rectangular phase modulation is applied in which the modulation phase is reversed by 180 degrees with each passage of the zero point of the sinusoidal modulation, as a result of which all the energy of the carrier frequency is pumped into the side components ω₀– 3Ω/2 and ω₀+ 3Ω/2 (Fig.17) (3Ω/2 is the frequency of the modulating radio frequency signal for phase modulation, where – Ω is equal to the frequency of the modulating radio frequency signal for amplitude modulation), as a result of which two-frequency radiation appears at frequencies ω₀– 3Ω/2 and ω₀+ 3Ω/2 (Fig.17), thus, the multiphoton carrier frequency is excluded from the quantum transmission channel. The source of the square wave signal is the radio frequency signal converter of the transmitter 12. The phase adjustment of the square wave, in order to obtain ideal carrier suppression in the signal structure, is carried out in the phase adjustment device of the transmitter 11. Further, two-frequency radiation at frequencies ω₀– 3Ω/2 and ω₀+ 3Ω/2 (Fig.17) is attenuated to a single-photon level using attenuator 8 (Fig.18). Received at the output of the attenuator 8 single-photon two-frequency radiation at frequencies ω₀– 3Ω/2 and ω₀+ 3Ω/2 (Fig. 18) is transmitted to the receiving device 3 through a fiber-optic communication line 1, which is a quantum channel that connects the transmitting device 2 to the receiving device 3. Single-photon dual-frequency radiation at frequencies ω₀– 3Ω/2 and ω₀+ 3Ω/2 (Fig.18) in the receiver 3 enters the input of the spectral filter 15, where the spectral components of the radiation are separated. Single-photon two-frequency radiation at frequencies ω₀– 3Ω/2 and ω₀+ 3Ω/2 (Fig.18) goes through the fourth output of the spectral filter 15 and enters the input of the third receiver of single photons 19, where the fact of receiving a photon is detected.

, на передающем устройстве 2, источником монохроматического излучения 5 генерируется световой пучок с частотой ω₀ (фиг.10). Дальше излучение подвергается амплитудной модуляции в электрооптическом амплитудном модуляторе передающего устройства 6. В данном случае применяется амплитудная модуляция, напряжением с частотой 2Ω в «нулевой» рабочей точке амплитудного модулятора передающего устройства 6. Источником синусоидального сигнала является генератор радиочастотного сигнала передающего устройства 10. В результате амплитудной модуляции на выходе электрооптического амплитудного модулятора передающего устройства 5 появляется двухчастотное излучение на частотах ω₀ – 2Ω и ω₀ + 2Ω (фиг.19), (Ω – частота модулирующего радиочастотного сигнала для амплитудной модуляции). Далее амплитудно-модулированный излучение (фиг.19), проходит через открытый электрооптический фазовый модулятор передающего устройства 7 без модуляции. Далее двухчастотное излучение (фиг.19) ослабляется до однофотонного уровня с помощью аттенюатора 8 (фиг.20). Полученный на выходе аттенюатора 8 однофотонное двухчастотное излучение на частотах ω₀ – 2Ω и ω₀ + 2Ω (фиг.20), передается на приемное устройство 3 через волоконно-оптическую линию связи 1, которая представляющей собой квантовый канал, который соединяет передающее устройство 2 с приемным устройством 3. Однофотонное двухчастотное излучение на частотах ω₀ – 2Ω и ω₀ + 2Ω (фиг.20) в приемном устройстве 3 попадает на вход спектрального фильтра 12, где разделяются спектральные составляющие излучения. Однофотонное двухчастотное излучение на частотах ω₀ – 2Ω и ω₀ + 2Ω (фиг.20) выходит через пятый выход спектрального фильтра 15 и попадает на вход четвертого приемника одиночных фотонов 20, где детектируется факт приема фотона.To transmit the fourth of the four orthogonal photon states, the state

, on the transmitter 2, the source of monochromatic radiation 5 generates a light beam with a frequency ω₀(Fig.10). Further, the radiation is subjected to amplitude modulation in the electro-optical amplitude modulator of the transmitter 6. In this case, amplitude modulation is applied, with a voltage with a frequency of 2Ω at the "zero" operating point of the amplitude modulator of the transmitter 6. The source of the sinusoidal signal is the RF signal generator of the transmitter 10. As a result of the amplitude modulation at the output of the electro-optical amplitude modulator of the transmitter 5, two-frequency radiation appears at frequencies ω₀– 2Ω and ω₀+ 2Ω (Fig.19), (Ω is the frequency of the modulating RF signal for amplitude modulation). Next, the amplitude-modulated radiation (Fig.19) passes through an open electro-optical phase modulator of the transmitter 7 without modulation. Next, the two-frequency radiation (Fig.19) is attenuated to a single-photon level using the attenuator 8 (Fig.20). Received at the output of the attenuator 8 single-photon two-frequency radiation at frequencies ω₀– 2Ω and ω₀+ 2Ω (Fig.20) is transmitted to the receiver 3 through a fiber-optic communication line 1, which is a quantum channel that connects the transmitter 2 to the receiver 3. Single-photon dual-frequency radiation at frequencies ω₀– 2Ω and ω₀+ 2Ω (Fig.20) in the receiving device 3 enters the input of the spectral filter 12, where the spectral components of the radiation are separated. Single-photon two-frequency radiation at frequencies ω₀– 2Ω and ω₀+ 2Ω (Fig.20) exits through the fifth output of the spectral filter 15 and enters the input of the fourth receiver of single photons 20, where the fact of receiving a photon is detected.

Multiphoton radiation at a carrier frequency ω ₀ (Fig.10), is a reference signal that may contain information to synchronize the operation of the elements of the transmitter 2 and receiver 3, passes through the first output of the spectral filter 15 and enters the classical radiation receiver 16.

Data received from the classical radiation receiver 16, from the first single photon receiver 17, from the second single photon receiver 18, from the third single photon receiver 19, from the fourth single photon receiver 20, are transmitted through the first, second, third, fourth and fifth outputs, respectively. devices for quantum distribution of a cryptographic key with frequency coding to a computer (which is not shown in the diagram), and further processing of this data is performed on a computer. Analyzing signals at the carrier frequency ω₀ (Fig.10) and at subcarrier frequencies ω₀– Ω and ω₀+ Ω (Fig.11), ω₀– Ω/2 and ω₀+ Ω/2 (Fig.15), ω₀– 3Ω/2 and ω₀+ 3/2Ω (Fig.18), ω₀– 2Ω and ω₀+ 2Ω (Fig.20) the transmitter 2 and the receiver 3 receive a secret cryptographic key and conclude that an eavesdropping intruder is present.

A device for quantum distribution of a cryptographic key with frequency encoding can be implemented on the following elements, designed to operate at a wavelength of 1550 nm (other wavelengths are possible):

- fiber-optic communication line 1, is a single-mode fiber SMF-28 1550 nm from various manufacturers. For example: reference cords or cables on SMF-28 fiber from Corning, TELECOM-TEST from LLC Production and Trade Company SOKOL, JSC OFS RUS Fiber Optic Cable Company, CJSC Samara Optical Cable Company, CJSC ”VIKTAN” – REPRESENTATIVE IN THE RUSSIAN FEDERATION PJSC PLANT YUZHKABEL, Broadcom Limited (Singapore and USA), Fiber Instrument Sales Inc. (USA), Eoptolink Technology Inc., Ltd. (China), Sumix (USA), OPTOKON a.s. (Czech Republic), Optoway Technologies Inc. (Taiwan), Kamaxoptic Communication Co., Ltd. (Shenzhen, China), Kaiphone Technology Co., Ltd. (China), Industrial Fiber Optics (USA), Allray Inc. (China), Nestor Cables Oy (Finland), etc.

The devices included in the transmitter 2 can be implemented on the following elements:

- monochromatic radiation source 5, can be made as a single-frequency semiconductor laser with a fiber output, with a tunable wavelength in the range of 1510-1560 nm and a tunable output power from 3 to 10 mW of various manufacturers. For example: PHOENIX 1200 - tunable laser - from LUNA Luna Innovations Incorporated (USA) or PHOENIX 1000 - tunable ECDL lasers - from LUNA Luna Innovations Incorporated (USA) or 1752A - 1.5 μm laser diodes of DOCSIS 3.1 standard - from EMCORE (USA) , ID300 short-pulse laser source - ID Quantique (Switzerland), etc.

- an electro-optical amplitude modulator of the transmitter 6, can be built on a lithium niobate crystal (LiNbO3) with a transmission loss of 2.5-3 dB from various manufacturers. For example: MXAN-LN-10 - analog 1550 nm 12 GHz optical modulator - from iXBlue Photonics (France), LN81S-FC - Zero-Chirp, 10 GHz Intensity Mod., Integrated PD and Replaceable GPO Conn, FC / PC - from Thorlabs (USA), LN82S-FC - Fixed-Chirp, 10 GHz Intensity Mod., Integrated PD and Replaceable GPO Connector, FC/PC - Thorlabs (USA) LN58S-FC - 20 GHz Low Vpi Analog Modulator, FC/PC Connectorized - Thorlabs (USA), etc.

- an electro-optical phase modulator of the transmitter 7, can be built on a lithium niobate crystal (LiNbO3) with a transmission loss of 2.5-3 dB from various manufacturers. For example MPZ-LN-10 - 1550 nm 12 GHz phase modulator - iXBlue Photonics (France), LN65S-FC - 10 GHz Phase Modulator with Polarizer, FC / PC Connectors - Thorlabs (USA), LN53S-FC - 10 GHz Phase Modulator without Polarizer, FC/PC Connectors from Thorlabs (USA), etc.

- attenuator 8 can be made as a single-mode adjustable attenuator from various manufacturers. For example: VOA50-APC - Single mode adjustable attenuator, operating wavelength: 1310/1550 nm, max. attenuation: 50 dB, connectors: FC/APC, - Thorlabs (USA), VOA50-FC - Single-mode adjustable attenuator, operating wavelength: 1310/1550 nm, max. attenuation: 50 dB, connectors: FC / PC, - Thorlabs (USA), VOA50 - Single-mode adjustable attenuator, operating wavelength: 1310/1550 nm, max. attenuation: 50 dB, without connectors - Thorlabs (USA), V1550F - Electronic variable attenuator, operating range: 1250 - 1650 nm, connector: FC / PC, - Thorlabs (USA), etc.

- the phase shifter of the transmitter 9 can be implemented as a programmable phase shifter. For example: LPS-402 2 GHz programmable USB phase shifter and LPS-802 4 GHz programmable USB phase shifter from Vaunix (USA)

- the RF signal generator of the transmitter 10 can be implemented as a programmable USB signal generator. For example: LMS-802DX 2.0 - 8.0 GHz programmable USB signal generator - Vaunix (USA)

- the device for adjusting the phase of the transmitter 11 can be made as a programmable phase shifter. For example: LPS-402 2 GHz programmable USB phase shifter and LPS-802 4 GHz programmable USB phase shifter from Vaunix (USA)

- the converter of the radio frequency signal of the transmitter 12, can be made as a Schmitt trigger. For example: SN74LVC2G17 Dual Schmitt-Trigger Buffer - Texas Instruments (USA)

The devices included in the receiving device 3 can be implemented on the following elements:

- electro-optical phase modulator of the receiving device 13, can be built on a lithium niobate crystal (LiNbO3) with a transmission loss of 2.5-3 dB from various manufacturers. For example MPZ-LN-10 - 1550 nm 12 GHz phase modulator - iXBlue Photonics (France), LN81S-FC - Zero-Chirp, 10 GHz Intensity Mod., Integrated PD and Replaceable GPO Conn, FC/PC - Thorlabs (USA) ), LN82S-FC - Fixed-Chirp, 10 GHz Intensity Mod., Integrated PD and Replaceable GPO Connector, FC/PC from Thorlabs (USA), etc.

- electro-optical amplitude modulator of the receiving device 14, can be built on a lithium niobate crystal (LiNbO3) with a transmission loss of 2.5-3 dB from various manufacturers. For example: MXAN-LN-10 - analog 1550 nm 12 GHz optical modulator - iXBlue Photonics (France), LN65S-FC - 10 GHz Phase Modulator with Polarizer, FC / PC Connectors - Thorlabs (USA), LN53S-FC - 10 GHz Phase Modulator without Polarizer, FC/PC Connectors from Thorlabs (USA), etc.

- spectral filter 15, is multi-channel and has five outputs, can be made as a multi-channel splitter, at the outputs of which fiber-optic Bragg gratings with a phase π-shift are recorded, tuned to the carrier or side components of the photon carrier. Fiber-optic Bragg gratings with a phase π-shift recorded on SMF-28 fiber at the NTsVO "Photonics" (Moscow), NII PREFZhS KNRTU-KAI (Kazan), Inversion-Fiber (Novosibirsk), Inversion-Sensor (Perm), etc. .d.

- classical radiation receiver 16, can be made as an SFP transmitter of various manufacturers and different ranges (for example: 3 km, 20 km, 40 km, 80 km, 120 km) - NetLink (China), GIGALINK (Russia), Cisco (USA), Strela (Russia)

- the first single photon detector 17 can be made as a single photon detector on silicon avalanche diodes of various manufacturers. For example: models ID230, ID210, ID220, ID280 - from ID Quantique (Switzerland)

- the second single photon receiver 18 can be made as a single photon detector on silicon avalanche diodes of various manufacturers. For example: models ID230, ID210, ID220, ID280 - from ID Quantique (Switzerland)

- the third receiver of single photons 19 can be made as a detector of single photons on silicon avalanche diodes of various manufacturers. For example: models ID230, ID210, ID220, ID280 - from ID Quantique (Switzerland)

- the fourth single photon receiver 20 can be made as a single photon detector based on silicon avalanche diodes of various manufacturers. For example: models ID230, ID210, ID220, ID280 - from ID Quantique (Switzerland)

- the phase shifter of the receiving device 21 can be implemented as a programmable phase shifter. For example: LPS-402 2 GHz Programmable USB Phase Shifter or LPS-802 4 GHz Programmable USB Phase Shifter from Vaunix (USA)

- the RF signal generator of the receiving device 22 can be implemented as a programmable USB signal generator. For example: LMS-802DX 2.0 - 8.0 GHz programmable USB signal generator - Vaunix (USA)

- the device for adjusting the phase of the receiving device 23 can be made as a programmable phase shifter. For example: LPS-402 2 GHz programmable USB phase shifter and LPS-802 4 GHz programmable USB phase shifter from Vaunix (USA)

- the converter of the radio frequency signal of the receiving device 24, can be made as a Schmitt trigger. For example: SN74LVC2G17 Dual Schmitt-Trigger Buffer - Texas Instruments (USA)

Synchronization block 4 can be made as a generator of control signals for synchronization of measuring and computing systems. For example: ME-020B synchronization unit - MERA Research and Production Enterprise (Russia).

The claimed invention allows to achieve the technical result of increasing the protection of a quantum cryptographic key, due to several modes of operation of the device, namely the mode of active detection of the state of photons and the mode of passive detection of the state of photons.

Claims (1)

A device for quantum distribution of a cryptographic key with frequency coding, comprising a transmitting device and a receiving device connected to each other by a fiber-optic communication line; wherein the transmitter contains a source of monochromatic radiation, the output of which is optically coupled to the input of the electro-optical amplitude modulator of the transmitter, the control input of the electro-optical amplitude modulator of the transmitter is connected to the output of the phase shifter of the transmitter, the output of the electro-optical amplitude modulator of the transmitter is optically coupled to the input of the electro-optical phase modulator of the transmitting device, the control input of the electro-optical phase modulator of the transmitting device is connected to the output of the radio frequency signal converter of the transmitting device, the output of the electro-optical phase modulator of the transmitting device is optically coupled to the input of the attenuator, the output of the attenuator is optically coupled to the input of the fiber-optic communication line, the transmitting device also contains a radio frequency signal generator transmitting device, the first output of which is connected to the input of the device with phase shift of the transmitting device; wherein the receiving device includes an electro-optical phase modulator of the receiving device, the input of which is optically coupled to the output of the fiber-optic communication line, the control input of the electro-optical phase modulator of the receiving device is connected to the output of the RF signal converter of the receiving device, the output of the electro-optical phase modulator of the receiving device is optically coupled to the input of the electro-optical amplitude modulator of the receiving device, the control input of the electro-optical amplitude modulator of the receiving device is connected to the output of the phase shifter of the receiving device, the input of the phase shifter of the receiving device is connected to the first output of the radio frequency signal generator of the receiving device, the receiving device also contains a spectral filter, the first output of which is optically coupled to the input of the classical radiation receiver, the output of the classical radiation receiver is the first output of the quantum frequency-coded cryptographic key distribution, the receiving device also contains the first single photon receiver, the output of which is the second output of the frequency-coded cryptographic key quantum distribution device, while the first and second outputs of the synchronization unit are connected to the synchronization inputs of the radio frequency signal generator of the transmitting device and the radio frequency generator. signal of the receiving device, respectively, the third and fourth outputs of the synchronization unit are connected to the synchronization inputs of the phase shift device of the transmitting device and the phase shift device of the receiving device, respectively, characterized in that a device for adjusting the phase of the transmitting device is additionally introduced into the transmitting device, the output of which is connected to the input of the radio frequency converter signal of the transmitting device, the input of the phase adjustment device of the transmitting device is connected to the second output of the RF signal generator p transmitting device; at the same time, a device for adjusting the phase of the receiving device is also additionally introduced into the receiving device, the output of which is connected to the input of the radio frequency signal converter of the receiving device, the input of the phase adjusting device of the receiving device is connected to the second output of the generator of the radio frequency signal of the transmitting device, in the receiving device the spectral filter is multichannel and has five outputs, the input of the spectral filter is optically coupled to the output of the electro-optical amplitude modulator of the receiving device, the second output of the spectral filter is optically coupled to the input of the first single photon receiver, the second single photon receiver is additionally introduced into the receiving device, the output of which is the third output of the cryptographic key quantum distribution device with frequency coding, the input of the second single photon receiver is optically coupled to the third output of the spectral filter, the third single photon receiver, the output of which is the fourth output of the frequency-coded cryptographic key quantum distribution device, the input of the third single photon receiver is optically coupled to the fourth output of the spectral filter, the fourth single photon receiver, the output of which is the fifth output of the frequency-coded cryptographic key quantum distribution device, the input of the fourth single photon receiver is optically coupled to the fifth spectral filter output; as well as the synchronization unit has the fifth and sixth outputs, while the fifth and sixth outputs of the synchronization unit are connected to the synchronization inputs of the transmitter phase adjustment device and the receiver phase adjustment device, respectively.

Images