RU2784023C1 - Quantum distribution device for a cryptographic key with frequency coding - Google Patents

Abstract

FIELD: cryptographic key quantum distribution systems.

SUBSTANCE: invention relates to systems for quantum distribution of a cryptographic key. The device for quantum distribution of a cryptographic key with frequency coding contains a transmitting device and a receiving device connected to each other by a fiber-optic communication line. The transmitter includes a source of monochromatic radiation, an electro-optical amplitude modulator of the transmitter, an electro-optical phase modulator of the transmitter, an attenuator, a phase shifter of the transmitter, an RF signal generator of the transmitter, and an RF signal converter of the transmitter. The receiving device includes a spectral filter, a classical radiation receiver, the first single photon receiver, the goal is achieved by the fact that the transmitter phase adjustment device is additionally introduced into the transmitter, while the spectral filter in the receiver is multichannel and has five outputs, also in the receiver The device additionally introduced a second single photon receiver, a third single photon receiver, a fourth single photon receiver.

EFFECT: reduction of the quantum error rate, due to completely passive filtering of data on the receiving device.

1 cl, 12 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 the disadvantage of a high quantum error rate, which, in turn, leads to insufficient reliability of the distribution of the cryptographic key over the quantum channel, and to an increase in the processing time of the cryptographic key on the receiving device.

The technical problem is the creation of a device for quantum distribution of a cryptographic key with frequency coding, which makes it possible to reduce the quantum error rate due to completely passive data filtering on the receiving device, which will increase the reliability of sending a cryptographic key over a quantum channel and reduce the processing time of the cryptographic key on the receiving device.

The technical result of the proposed invention is to reduce the quantum error rate due to completely passive filtering of data on the receiving device.

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 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, the receiving device also contains the first single photon receiver, the output of which is by the second output of the device for quantum distribution of a cryptographic key with frequency coding, 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 signal converter of the transmitting device, the input of the phase adjusting device of the transmitting device is connected to the second output of the radio frequency signal generator transmitting device, and also, 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 fibers onno-optical communication line, the second output of the spectral filter is optically coupled to the input of the first single photon receiver; also, the second single photon receiver is additionally introduced into the receiving device, the output of which is the third output of the device for quantum distribution of a cryptographic key with frequency coding, the input of the second single photon receiver 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 spreader, 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 devices for quantum distribution of a cryptographic key with frequency coding, the input of the fourth receiver of single photons is optically coupled to the fifth output of the spectral filter.

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 a two-frequency amplitude-modulated signal at a frequency Ω, at the output of the electro-optical amplitude modulator of the transmitter. Figure 4 - the frequency spectrum of a single-photon two-frequency amplitude-modulated signal at a frequency Ω, at the output of the attenuator. Figure 5 - the frequency spectrum of the amplitude-modulated signal at a frequency Ω, at the output of the electro-optical amplitude modulator of the transmitter. Figure 6 - 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. Figure 7 - the frequency spectrum of a single-photon phase-switched signal at a frequency of Ω/2, at the output of the attenuator. In Fig.8 - the frequency spectrum of the amplitude-modulated signal at a frequency Ω, at the output of the electro-optical amplitude modulator of the transmitter. Figure 9 - 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. Figure 10 shows the frequency spectrum of a single-photon phase-switched signal at a frequency of Ω/2 at the output of the attenuator. In Fig.11 - 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.12 - 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 interconnected fiber-optic communication line 1, the transmitter 2 and the receiver 3; while the transmitter 2 includes: optically coupled in series, a source of monochromatic radiation 4, an electro-optical amplitude modulator of the transmitter 5, an electro-optical phase modulator of the transmitter 6 and an attenuator 7, the output of the attenuator 7 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 8, the input of the phase shifter of the transmitter 8 is connected to the first output of the RF signal generator of the transmitter 9, and the output of the phase shifter of the transmitter 8 is connected to the control input of the electro-optical amplitude modulator of the transmitter 5 , the second output of the RF signal generator of the transmitter 9 is connected to the input of the phase adjustment device of the transmitter 10, the output of the phase adjustment device of the transmitter 10 is connected to the input of the RF converter a signal from the transmitter 11, the output of the radio frequency signal converter of the transmitter 11 is connected to the control input of the electro-optical phase modulator of the transmitter 6, the first and second outputs of the RF signal generator of the transmitter 9 are identical to each other; wherein the receiving device 3 includes: the spectral filter 12 is multichannel and has five outputs, the first output of the spectral filter 12 is optically coupled to the input of the classical radiation receiver 13, the output of the classical radiation receiver 13 is the first output of the device for quantum distribution of a cryptographic key with frequency coding, the second output of the spectral filter 12 is optically coupled to the input of the first single photon receiver 14; the receiver of single photons 15 is the third output of the quantum distribution device of the cryptographic key with frequency coding, the fourth output of the spectral filter 12 is optically coupled to the input of the third receiver of single photons 16, the output tr the third single photon receiver 16 is the fourth output of the frequency-coded cryptographic key quantum distribution device, the fifth output of the spectral filter system 12 is optically coupled to the input of the fourth single-photon receiver 17, the output of the fourth single-photon receiver 17 is the fifth output of the frequency-coded cryptographic key quantum distribution device , while the input of the spectral filter 12 is the input of the receiver 3 and is optically coupled to the output of the fiber-optic communication line 1, while the elements that make up the transmitter 2, the monochromatic radiation source 4, the attenuator 7, the phase shift device of the transmitter 8, RF signal generator of the transmitter 9, phase adjuster of the transmitter 10, RF signal converter of the transmitter 11, and elements included in the receiver 3, classical radiation receiver 13, ne The first single photon receiver 14, the second single photon receiver 15, the third single photon receiver 16, the fourth single photon receiver 17 have a power supply system, which is not shown in the diagram.

Let's consider the device of quantum distribution of a cryptographic key with frequency coding shown in Fig.1 in work. 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 4, the attenuator 7, the phase shift device of the transmitter 8, the radio frequency signal generator of the transmitter 9, the device for adjusting the phase of the transmitter 10, the converter of the radio frequency signal of the transmitter device 11, and the elements included in the receiver 3, classical radiation receiver 13, the first single photon receiver 14, the second single photon receiver 15, the third single photon receiver 16, the fourth single photon receiver 17.

, на передающем устройстве 2, источником монохроматического излучения 4 генерируется световой пучок с частотой ω₀ (фиг.2). Дальше излучение подвергается амплитудной модуляции в электрооптическом амплитудном модуляторе передающего устройства 5. В данном случае применяется амплитудная модуляция, напряжением с частотой Ω в «нулевой» рабочей точке амплитудного модулятора передающего устройства 5. Источником синусоидального сигнала является генератор радиочастотного сигнала передающего устройства 9. В результате амплитудной модуляции на выходе электрооптического амплитудного модулятора передающего устройства 5 появляется двухчастотное излучение на частотах ω₀ – Ω и ω₀ + Ω (фиг.3), (Ω – частота модулирующего радиочастотного сигнала для амплитудной модуляции). Далее амплитудно-модулированный излучение (фиг.3), проходит через открытый электрооптический фазовый модулятор передающего устройства 6 без модуляции. Далее двухчастотное излучение (фиг.3) ослабляется до однофотонного уровня с помощью аттенюатора 7 (фиг.4). Полученный на выходе аттенюатора 7 однофотонное двухчастотное излучение на частотах ω₀ – Ω и ω₀ + Ω (фиг.4), 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.4) в приемном устройстве 3 попадает на вход спектрального фильтра 12, где разделяются спектральные составляющие излучения. Однофотонное двухчастотное излучение на частотах ω₀ – Ω и ω₀ + Ω (фиг.4) выходит через второй выход спектрального фильтра 12 и попадает на вход первого приемника одиночных фотонов 14, 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 4 generates a light beam with a frequency ω₀(figure 2). Further, the radiation is subjected to amplitude modulation in the electro-optical amplitude modulator of the transmitting device 5. 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 5. The source of the sinusoidal signal is the RF signal generator of the transmitting device 9. 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– Ω and ω₀+Ω (Fig.3), (Ω is the frequency of the modulating RF signal for amplitude modulation). Next, the amplitude-modulated radiation (figure 3) passes through an open electro-optical phase modulator of the transmitter 6 without modulation. Next, the two-frequency radiation (figure 3) is attenuated to a single-photon level using the attenuator 7 (figure 4). Received at the output of the attenuator 7 single-photon two-frequency radiation at frequencies ω₀– Ω and ω₀+Ω (Fig.4) 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 and ω₀+Ω (figure 4) in the receiver 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– Ω and ω₀+Ω (Fig.4) goes through the second output of the spectral filter 12 and enters the input of the first receiver of single photons 14, where the fact of receiving a photon is detected.

, на передающем устройстве 2, источником монохроматического излучения 4 генерируется световой пучок с частотой ω₀ (фиг.2). Дальше излучение подвергается амплитудной модуляции в электрооптическом амплитудном модуляторе передающего устройства 5. В данном случае применяется амплитудная модуляция при работе электрооптического амплитудного модулятора передающего устройства 5 на линейном участке напряжением с частотой Ω и коэффициентом амплитудной модуляции m=0,55. Источником синусоидального сигнала является генератор радиочастотного сигнала передающего устройства 9. В результате амплитудной модуляции на выходе электрооптического амплитудного модулятора передающего устройства 5 появляется излучение в спектре которого формируются две боковые частоты ω₀ – Ω и ω₀ + Ω (фиг.5), отстоящие от основной частоты оптического сигнала ω₀ на величину частоты Ω (фиг.5) (Ω – частота модулирующего радиочастотного сигнала для амплитудной модуляции). Далее амплитудно-модулированное излучение проходит фазовую коммутацию в электрооптическом фазовом модуляторе передающего устройства 6, 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.6) (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.6). тем самым, из квантового канала передачи исключается многофотонная несущая частота. Источником прямоугольного сигнала является преобразователь радиочастотного сигнала передающего устройства 11. Подстройка фазы прямоугольного сигнала, для получения идеального подавления несущей в структуре сигнала, осуществляется в устройстве подстройки фазы передающего устройства 10. Далее двухчастотное излучение на частотах ω₀ – Ω/2 и ω₀ + Ω/2 (фиг.6) ослабляется до однофотонного уровня с помощью аттенюатора 7 (фиг.7). Полученный на выходе аттенюатора 7 однофотонное двухчастотное излучение на частотах ω₀ – Ω/2 и ω₀ + Ω/2 (фиг.7), 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.7) в приемном устройстве 3 попадает на вход спектрального фильтра 12, где разделяются спектральные составляющие излучения. Однофотонное двухчастотное излучение на частотах ω₀ – Ω/2 и ω₀ + Ω/2 (фиг.7) выходит через третий выход спектрального фильтра 12 и попадает на вход второго приемника одиночных фотонов 15, 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 4 generates a light beam with a frequency ω₀(figure 2). Further, the radiation is subjected to amplitude modulation in the electro-optical amplitude modulator of the transmitting device 5. In this case, amplitude modulation is applied when the electro-optical amplitude modulator of the transmitting device 5 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 RF signal generator of the transmitting device 9. As a result of amplitude modulation, at the output of the electro-optical amplitude modulator of the transmitting device 5, radiation appears in the spectrum of which two side frequencies ω are formed.₀ – Ω and ω₀ + Ω (Fig.5), spaced from the main frequency of the optical signal ω₀ by the value of the frequency Ω (Fig.5) (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 6, 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.6) (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.6). 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 11. 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 10. Further, two-frequency radiation at frequencies ω₀– Ω/2 and ω₀+ Ω/2 (Fig.6) is attenuated to a single-photon level using the attenuator 7 (Fig.7). Received at the output of the attenuator 7 single-photon two-frequency radiation at frequencies ω₀– Ω/2 and ω₀+ Ω/2 (Fig.7) 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.7) in the receiver 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– Ω/2 and ω₀+ Ω/2 (Fig.7) goes through the third output of the spectral filter 12 and enters the input of the second receiver of single photons 15, where the fact of receiving a photon is detected.

, на передающем устройстве 2, источником монохроматического излучения 4 генерируется световой пучок с частотой ω₀ (фиг.2). Дальше излучение подвергается амплитудной модуляции в электрооптическом амплитудном модуляторе передающего устройства 5. В данном случае применяется амплитудная модуляция при работе электрооптического амплитудного модулятора передающего устройства 5 на линейном участке напряжением с частотой

и коэффициентом амплитудной модуляции m=0,55. Источником синусоидального сигнала является генератор радиочастотного сигнала передающего устройства 9. В результате амплитудной модуляции на выходе электрооптического амплитудного модулятора передающего устройства 5 появляется излучение в спектре которого формируются две боковые частоты ω₀ – Ω и ω₀ + Ω (фиг.8), отстоящие от основной частоты оптического сигнала ω₀ на величину частоты Ω (фиг.8) (Ω – частота модулирующего радиочастотного сигнала для амплитудной модуляции). Далее амплитудно-модулированное излучение проходит фазовую коммутацию в электрооптическом фазовом модуляторе передающего устройства 6, 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.9) (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.9), тем самым, из квантового канала передачи исключается многофотонная несущая частота. Источником прямоугольного сигнала является преобразователь радиочастотного сигнала передающего устройства 11. Подстройка фазы прямоугольного сигнала, для получения идеального подавления несущей в структуре сигнала, осуществляется в устройстве подстройки фазы передающего устройства 10. Далее двухчастотное излучение на частотах ω₀ – 3Ω/2 и ω₀ + 3Ω/2 (фиг.9) ослабляется до однофотонного уровня с помощью аттенюатора 7 (фиг.10). Полученный на выходе аттенюатора 7 однофотонное двухчастотное излучение на частотах ω₀ – 3Ω/2 и ω₀ + 3Ω/2 (фиг.10), 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.10) в приемном устройстве 3 попадает на вход спектрального фильтра 12, где разделяются спектральные составляющие излучения. Однофотонное двухчастотное излучение на частотах ω₀ – 3Ω/2 и ω₀ + 3Ω/2 (фиг.10) выходит через четвертый выход спектрального фильтра 12 и попадает на вход третьего приемника одиночных фотонов 16, 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 4 generates a light beam with a frequency ω₀(figure 2). Further, the radiation is subjected to amplitude modulation in the electro-optical amplitude modulator of the transmitting device 5. In this case, amplitude modulation is applied when the electro-optical amplitude modulator of the transmitting device 5 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 RF signal generator of the transmitting device 9. As a result of amplitude modulation, at the output of the electro-optical amplitude modulator of the transmitting device 5, radiation appears in the spectrum of which two side frequencies ω are formed.₀ – Ω and ω₀ + Ω (Fig.8), separated from the main frequency of the optical signal ω₀ by the value of the frequency Ω (Fig.8) (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 6, 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.9) (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.9), 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 11. The phase adjustment of the square wave signal, in order to obtain ideal carrier suppression in the signal structure, is carried out in the phase adjustment device of the transmitter 10. Further, two-frequency radiation at frequencies ω₀– 3Ω/2 and ω₀+ 3Ω/2 (Fig.9) is attenuated to a single-photon level using the attenuator 7 (Fig.10). Received at the output of the attenuator 7 single-photon two-frequency radiation at frequencies ω₀– 3Ω/2 and ω₀+ 3Ω/2 (Fig. 10) 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.10) in the receiver 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– 3Ω/2 and ω₀+ 3Ω/2 (Fig.10) goes through the fourth output of the spectral filter 12 and enters the input of the third receiver of single photons 16, where the fact of receiving a photon is detected.

, на передающем устройстве 2, источником монохроматического излучения 4 генерируется световой пучок с частотой ω₀ (фиг.2). Дальше излучение подвергается амплитудной модуляции в электрооптическом амплитудном модуляторе передающего устройства 5. В данном случае применяется амплитудная модуляция, напряжением с частотой 2Ω в «нулевой» рабочей точке амплитудного модулятора передающего устройства 5. Источником синусоидального сигнала является генератор радиочастотного сигнала передающего устройства 9. В результате амплитудной модуляции на выходе электрооптического амплитудного модулятора передающего устройства 5 появляется двухчастотное излучение на частотах ω₀ – 2Ω и ω₀ + 2Ω (фиг.11), (Ω – частота модулирующего радиочастотного сигнала для амплитудной модуляции). Далее амплитудно-модулированный излучение (фиг.11), проходит через открытый электрооптический фазовый модулятор передающего устройства 6 без модуляции. Далее двухчастотное излучение (фиг.11) ослабляется до однофотонного уровня с помощью аттенюатора 7 (фиг.12). Полученный на выходе аттенюатора 7 однофотонное двухчастотное излучение на частотах ω₀ – 2Ω и ω₀ + 2Ω (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 – 2Ω и ω₀ + 2Ω (фиг.12) 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.12) выходит через пятый выход спектрального фильтра 12 и попадает на вход четвертого приемника одиночных фотонов 17, где детектируется факт приема фотона.To transmit the fourth of the four orthogonal states of the photon, the state

, on the transmitter 2, the source of monochromatic radiation 4 generates a light beam with a frequency ω₀(figure 2). Further, the radiation is subjected to amplitude modulation in the electro-optical amplitude modulator of the transmitter 5. 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 5. The source of the sinusoidal signal is the RF signal generator of the transmitter 9. 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.11), (Ω is the frequency of the modulating RF signal for amplitude modulation). Next, the amplitude-modulated radiation (Fig.11) passes through an open electro-optical phase modulator of the transmitter 6 without modulation. Next, the two-frequency radiation (Fig.11) is attenuated to a single-photon level using the attenuator 7 (Fig.12). Received at the output of the attenuator 7 single-photon two-frequency radiation at frequencies ω₀– 2Ω and ω₀+ 2Ω (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– 2Ω and ω₀+ 2Ω (Fig.12) 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.12) goes through the fifth output of the spectral filter 12 and enters the input of the fourth receiver of single photons 17, where the fact of receiving a photon is detected.

Multiphoton radiation at a carrier frequency ω ₀ (Fig.2), 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 12 and enters the classical radiation receiver 13.

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 18, 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 carrier frequency ω₀ (figure 2) and on subcarrier frequencies ω₀– Ω and ω₀+ Ω (Fig.4), ω₀– Ω/2 and ω₀+ Ω/2 (Fig.7), ω₀– 3Ω/2 and ω₀+ 3/2Ω (Fig.10), ω₀– 2Ω and ω₀+ 2Ω (Fig.12) the transmitting device 2 and the receiving device 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 4, 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 value 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 from ID Quantique (Switzerland), etc.

- an electro-optical amplitude modulator of the transmitter 5, 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 6, 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 7 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 8 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 9 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 10 can be implemented as a programmable phase shifter. For example: LPS-402 programmable USB phase shifter with a bandwidth of 2 GHz and LPS-802 programmable USB phase shifter with a bandwidth of 4 GHz - Vaunix (USA),

- the converter of the radio frequency signal of the transmitter 11, 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:

- spectral filter 12 is multichannel and has five outputs; it can be made as a multichannel 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 13, 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 14 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 15 can be made as a single photon detector on silicon avalanche diodes of various manufacturers. For example: ID230, ID210, ID220, ID280 models - ID Quantique (Switzerland),

- the third single photon receiver 16 can be made as a single photon detector on silicon avalanche diodes of various manufacturers. For example: ID230, ID210, ID220, ID280 models - ID Quantique (Switzerland),

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

The claimed invention allows to achieve the technical result of reducing the quantum error rate due to completely passive data filtering at the receiving device.

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 phase shift of the transmitting device; wherein the receiving device includes 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, the receiving device also contains the first single photon receiver, the output of which is the second by the output of the device for quantum distribution of a cryptographic key with frequency coding, characterized in that the transmitting device is additionally equipped with a device for adjusting the phase of the transmitting device, the output of which is connected to the input of the radio frequency signal converter of the transmitting device, the input of the phase adjusting device of the transmitting device is connected to the second output of the radio frequency signal generator of the transmitting device, as well as 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 fiber nano-optical communication line, the second output of the spectral filter is optically coupled to the input of the first single photon receiver, also the second single photon receiver is additionally introduced into the receiving device, the output of which is the third output of the device for quantum distribution of a cryptographic key with frequency coding, the input of the second single photon receiver is optically is 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 device quantum distribution of a cryptographic key with frequency coding, the input of the fourth receiver of single photons is optically coupled to the fifth output of the spectral filter.

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