CN214281393U - Phase encoding quantum key distribution system - Google Patents
Phase encoding quantum key distribution system Download PDFInfo
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- CN214281393U CN214281393U CN202023329268.XU CN202023329268U CN214281393U CN 214281393 U CN214281393 U CN 214281393U CN 202023329268 U CN202023329268 U CN 202023329268U CN 214281393 U CN214281393 U CN 214281393U
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Abstract
The utility model discloses a phase coding quantum key distribution system, single photon source produce single photon pulse. The first optical coupler splits a single photon pulse generated by the single photon source into two paths of sub-optical pulses. And the multi-core optical fiber receives the two paths of sub-optical pulses output by the first optical coupler and transmits the sub-optical pulses to the second optical coupler. And the second optical coupler combines the two paths of sub-optical pulses and sends the combined beam to the single-photon detector. The first phase modulator and the second phase modulator are used for quantum key distribution system encoding and decoding phase modulation, respectively. The first phase modulator and the second phase modulator are arranged on different optical paths or the same optical path between the first optical coupler and the second optical coupler. The multi-core optical fiber is used for ensuring the consistency of environmental interference on the change of the length of the optical fiber, so that the scheme of the phase encoding equal-arm interferometer can be realized during long-distance transmission, the efficient quantum key distribution under the actual environmental interference can be supported, and the problem of low phase encoding efficiency of the unequal-arm interferometer is solved.
Description
Technical Field
The utility model relates to a secret communication technology field of optical transmission, concretely relates to phase coding quantum key distribution system.
Background
The quantum key distribution is the cross hotspot field combining quantum physics and information science, and based on the physical principles of quantum mechanics Heisebauer uncertain relation, quantum unclonable theorem and the like, the potential eavesdropping behavior can be detected, the secure sharing of encryption keys of two communication parties can be realized based on a public channel, and the method can be widely applied to the fields of high-security information transmission requirements of national defense, government affairs, finance, electric power and the like.
Ground quantum key distribution is mainly based on fiber channel transmission, and is widely applied to fiber quantum key distribution because phase encoding is insensitive to fiber channel birefringence. At present, the phase coding mainly adopts an unequal-arm interferometer scheme, three peaks exist in decoding interference, and only the middle interference peak contributes to key forming, so that the efficiency is low.
SUMMERY OF THE UTILITY MODEL
The utility model aims to solve is with the problem that the distribution efficiency is low of waitronic interferometer phase coding quantum key, provides a phase coding quantum key distribution system, and it realizes the distribution of phase coding quantum key through waiting the arm interferometer based on multicore optic fibre.
In order to solve the above problems, the utility model discloses a realize through following technical scheme:
a phase encoded quantum key distribution system, comprising: the single-photon detector comprises a single-photon source, a first optical coupler, a first phase modulator, a multi-core fiber, a second optical coupler, a second phase modulator and one or two single-photon detectors; the single photon source is used for generating single photon pulses; the first optical coupler comprises at least one input port and two output ports, and is used for receiving single photon pulses generated by a single photon source, splitting the single photon pulses generated by the single photon source into two paths of sub-optical pulses, and outputting the two paths of sub-optical pulses through the two output ports of the first optical coupler respectively; the multi-core optical fiber is a quantum channel and is used for transmitting two paths of sub-optical pulses output by two output ports of the first optical coupler; the number of the fiber cores of the multi-core optical fiber is not less than two, one of the fiber cores is connected with one of the two output ports of the first optical coupler and used for transmitting one of the two paths of sub-optical pulses, and the other fiber core is connected with the other of the two output ports of the first optical coupler and used for transmitting the other of the two paths of sub-optical pulses; the second optical coupler comprises two input ports and at least one output port, wherein one input port of the two input ports of the second optical coupler is connected with one fiber core which transmits one path of sub optical pulse in the multi-core optical fiber and is used for receiving one path of sub optical pulse; the other input port of the two input ports of the second optical coupler is connected with the other fiber core which transmits the other path of sub optical pulse in the multi-core optical fiber and is used for receiving the other path of sub optical pulse; one path of sub optical pulse and the other path of sub optical pulse are output by one or two output ports of the second optical coupler after being combined by the second optical coupler; the single-photon detector is used for detecting the single-photon pulse output by the output port of the second optical coupler; the first phase modulator is arranged on an optical path connecting one output port of the first optical coupler with one fiber core in the multi-core optical fiber or on an optical path connecting the other output port of the first optical coupler with the other fiber core in the multi-core optical fiber; the first phase modulator is used for encoding phase modulation of a quantum key distribution system; the second phase modulator is arranged on an optical path where one input port of the second optical coupler is connected with one fiber core in the multi-core optical fiber, or is arranged on an optical path where the other input port of the second optical coupler is connected with the other fiber core in the multi-core optical fiber; the second phase modulator is used for decoding phase modulation of the quantum key distribution system.
When one single-photon detector is used, the first phase modulator randomly modulates four phases of 0 degree, 90 th, 180 degrees or 270 degrees; the second phase modulator randomly modulates four phases of 0 degree, 90 th, 180 degree or 270 degree.
When the number of the single photon detectors is two, the first phase modulator randomly modulates four phases of 0 degree, 90 th, 180 degrees or 270 degrees; the second phase modulator randomly modulates two phases of 0 degree or 90 degrees.
In the scheme, the single photon source is a weak coherent light source and consists of a pulse laser and an optical attenuator; the pulse laser generates pulse light, and the attenuator attenuates the pulse light into single photon pulses.
The phase-encoded quantum key distribution system further comprises an intensity modulator; the intensity modulator is arranged on a light path between the single photon source and the first optical coupler and used for modulating the average photon number of the single photon light pulse.
The phase-encoded quantum key distribution system further comprises a polarization controller; the polarization controller is arranged on a light path connecting one output port of the first optical coupler with one fiber core in the multi-core optical fiber or arranged on a light path connecting the other output port of the first optical coupler with the other fiber core in the multi-core optical fiber; or on the optical path where one input port of the second optical coupler is connected to one core of the multicore fiber, or on the optical path where the other input port of the second optical coupler is connected to the other core of the multicore fiber.
An input side branch of the system is formed from an output end of the single photon source to an input port of the first optical coupler; an output port of the second optical coupler to an input end of the first single-photon detector form an output side branch of the system; an output port of the first optical coupler forms a quantum channel of the system through the first phase modulator, the multi-core optical fiber and the second phase modulator to an input port of the second optical coupler; wherein the number of the input side branches and the output side branches is more than 2. At this time:
the phase-encoding quantum key distribution system further comprises a first wavelength division multiplexer and/or a second wavelength division multiplexer; the first wavelength division multiplexer is arranged on a light path connecting one output port of the first optical coupler with one fiber core in the multi-core optical fiber; more than two beam splitting ends of the first wavelength division multiplexer are connected with one output port of the first optical coupler of each input side branch, and the beam combining end of the first wavelength division multiplexer is connected with one fiber core in the multi-core optical fiber; the second wavelength division multiplexer is arranged on the light path connecting the other output port of the first optical coupler with the other fiber core in the multi-core optical fiber; more than two beam splitting ends of the second wavelength division multiplexer are connected with the other output port of the first optical coupler of each input side branch, and the beam combining end of the first wavelength division multiplexer is connected with the other fiber core in the multi-core optical fiber.
The phase-encoding quantum key distribution system further comprises a first wavelength division demultiplexer and/or a second wavelength division demultiplexer; the first wavelength division demultiplexer is arranged on a light path connecting one input port of the second optical coupler with one fiber core in the multi-core optical fiber; the beam combining end of the first wavelength division demultiplexer is connected with one fiber core in the multi-core optical fiber, and more than two beam splitting ends of the first wavelength division demultiplexer are connected with one input port of the second optical coupler of each output side branch; the second wavelength division demultiplexer is arranged on the light path of the other input port of the second optical coupler connected with the other fiber core in the multi-core optical fiber; the beam combining end of the first wavelength division demultiplexer is connected with the other fiber core in the multi-core optical fiber, and more than two beam splitting ends of the second wavelength division demultiplexer are connected with the other input port of the second optical coupler of each output side branch.
Compared with the prior art, the utility model provides a high-efficient phase coding quantum key distribution system scheme of easily realizing and using can guarantee the uniformity of environmental disturbance to optical fiber length variation through using multicore optic fibre as quantum channel to can realize arm interferometer schemes such as phase coding when long distance transmission, can support high-efficient quantum key distribution under the actual environmental disturbance, avoid the problem that arm interferometer phase coding is inefficient.
Drawings
Fig. 1 is a schematic structural diagram of a first phase-encoded quantum key distribution system.
Fig. 2 is a schematic structural diagram of a second phase-encoded quantum key distribution system.
Fig. 3 is a schematic structural diagram of a third phase-encoded quantum key distribution system.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the following specific examples.
Example 1:
referring to fig. 1, a phase-encoded quantum key distribution system, comprising: the device comprises a single photon source, an intensity modulator, a first optical coupler, a first phase modulator, a polarization controller, a multi-core optical fiber, a second optical coupler, a second phase modulator and a first single photon detector.
A single photon source is used to generate single photon pulses. One possible configuration of a single photon source is a weakly coherent light source consisting of a pulsed laser that produces pulsed light and an optical attenuator that attenuates the light pulses into single photon pulses.
An intensity modulator is disposed between the single photon source and the first optical coupler for modulating the average photon count of the single photon light pulses.
The first optical coupler comprises at least one input port and two output ports and is used for receiving single photon pulses generated by a single photon source, splitting the single photon pulses generated by the single photon source into two paths of sub-optical pulses and outputting the two paths of sub-optical pulses through the two output ports of the first optical coupler respectively. In this embodiment, the first optical coupler is a 1 × 2 optical coupler.
The multi-core optical fiber is a quantum channel and is used for transmitting two paths of sub-optical pulses output by the two output ports of the first optical coupler. The number of the fiber cores of the multi-core optical fiber is not less than two, one of the fiber cores is connected with one of the two output ports of the first optical coupler and used for transmitting one of the two paths of sub-optical pulses, and the other fiber core is connected with the other of the two output ports of the first optical coupler and used for transmitting the other of the two paths of sub-optical pulses.
The second optical coupler comprises two input ports and at least one output port, wherein one input port of the two input ports of the second optical coupler is connected with one fiber core of the multi-core optical fiber for transmitting one path of sub optical pulse and used for receiving one path of sub optical pulse. And the other input port of the two input ports of the second optical coupler is connected with the other fiber core which transmits the other path of sub optical pulses in the multi-core optical fiber and is used for receiving the other path of sub optical pulses. And one path of sub optical pulse and the other path of sub optical pulse are combined by the second optical coupler and then output by an output port of the second optical coupler. In this embodiment, the second optical coupler is a 2 × 1 optical coupler.
The first single-photon detector is used for detecting the single-photon pulse output by the second optical coupler.
The polarization controller is used for controlling the polarization state of one of the two paths of sub-optical pulses. The polarization controller is arranged on an optical path connecting one output port of the first optical coupler and one fiber core in the multi-core fiber, or on an optical path connecting the other output port of the first optical coupler and the other fiber core in the multi-core fiber, or on an optical path connecting one input port of the second optical coupler and one fiber core in the multi-core fiber, or on an optical path connecting the other input port of the second optical coupler and the other fiber core in the multi-core fiber. In this embodiment, the polarization controller is disposed on the optical path connecting the other output port of the first optical coupler and the other core of the multi-core fiber.
The first phase modulator is used for encoding phase modulation of the quantum key distribution system, and the second phase modulator is used for decoding phase modulation of the quantum key distribution system. The first phase modulator and the second phase modulator are arranged on different optical paths or the same optical path between the output port of the first optical coupler and the input port of the second optical coupler. Taking the example of being arranged on the same optical path, namely: the first phase modulator is arranged on an optical path connecting one output port of the first optical coupler and one fiber core in the multi-core optical fiber. The first phase modulator randomly modulates four phases of 0 degree, 90 th, 180 degree or 270 degree. The second phase modulator is arranged on an optical path connecting one input port of the second optical coupler with one fiber core in the multi-core optical fiber. The second phase modulator randomly modulates four phases of 0 degree, 90 th, 180 degree or 270 degree.
The working process and principle of the phase coding quantum key distribution system are as follows: the single photon source generates single photon pulses and transmits the single photon pulses to the intensity modulator, the intensity modulator modulates the average photon number of the single photon pulses and transmits the single photon pulses to the input optical coupler, and the input optical coupler splits the single photon pulses into two paths of sub-optical pulses. One path of sub-optical pulse is output to a first phase modulator of coding phase modulation through an output port of a first optical coupler, is transmitted to one optical fiber of a double-core optical fiber after phase modulation, and is transmitted to an input port of a second optical coupler; and the other path of sub-optical pulse is output to the other optical fiber of the double-core optical fiber through the other output port of the first optical coupler, is transmitted to the second phase modulator for decoding phase modulation, is output to the other input port of the second optical coupler after phase modulation. And the second optical coupler combines the two paths of sub-optical pulses and outputs the combined light to the first single-photon detector through the output port, and generates a shared key according to a quantum key distribution protocol. The first phase modulator for encoding phase modulation randomly modulates the phase of 0 degree, 90 degrees, 180 degrees or 270 degrees, and the second phase modulator for decoding phase modulation randomly modulates the phase of 0 degree, 90 degrees, 180 degrees or 270 degrees.
Example 2:
referring to fig. 2, a phase-encoded quantum key distribution system, comprising: the device comprises a single photon source, an intensity modulator, a first optical coupler, a first phase modulator, a multi-core optical fiber, a second optical coupler, a second phase modulator, a first single photon detector and a second single photon detector.
A single photon source is used to generate single photon pulses. One possible configuration of a single photon source is a weakly coherent light source consisting of a pulsed laser that produces pulsed light and an optical attenuator that attenuates the light pulses into single photon pulses.
An intensity modulator is disposed between the single photon source and the first optical coupler for modulating the average photon count of the single photon light pulses.
The first optical coupler comprises at least one input port and two output ports and is used for receiving single photon pulses generated by a single photon source, splitting the single photon pulses generated by the single photon source into two paths of sub-optical pulses and outputting the two paths of sub-optical pulses through the two output ports of the first optical coupler respectively. In this embodiment, the first optical coupler is a 1 × 2 optical coupler.
The multi-core optical fiber is a quantum channel and is used for transmitting two paths of sub-optical pulses output by the two output ports of the first optical coupler. The number of the fiber cores of the multi-core optical fiber is not less than two, one of the fiber cores is connected with one of the two output ports of the first optical coupler and used for transmitting one of the two paths of sub-optical pulses, and the other fiber core is connected with the other of the two output ports of the first optical coupler and used for transmitting the other of the two paths of sub-optical pulses.
The second optical coupler comprises two input ports and at least one output port, wherein one input port of the two input ports of the second optical coupler is connected with one fiber core of the multi-core optical fiber for transmitting one path of sub optical pulse and used for receiving one path of sub optical pulse. And the other input port of the two input ports of the second optical coupler is connected with the other fiber core which transmits the other path of sub optical pulses in the multi-core optical fiber and is used for receiving the other path of sub optical pulses. And one path of sub optical pulse and the other path of sub optical pulse are combined by the second optical coupler and then output by two output ports of the second optical coupler. In this embodiment, the second optical coupler is a 2 × 2 optical coupler.
The first single-photon detector and the second single-photon detector are used for detecting the single-photon pulse output by the second optical coupler.
The first phase modulator is used for encoding phase modulation of the quantum key distribution system, and the second phase modulator is used for decoding phase modulation of the quantum key distribution system. The first phase modulator and the second phase modulator are arranged on different optical paths or the same optical path between the output port of the first optical coupler and the input port of the second optical coupler. Taking the arrangement on different optical paths as an example, the first phase modulator is arranged on the optical path where the other output port of the first optical coupler is connected with the other core in the multi-core fiber. The first phase modulator randomly modulates four phases of 0 degree, 90 th, 180 degree or 270 degree. The second phase modulator is arranged on an optical path connecting one input port of the second optical coupler with one fiber core in the multi-core optical fiber. The second phase modulator randomly modulates either the 0 degree or 90 second variety of phases.
The working process and principle of the phase coding quantum key distribution system are as follows: the single photon source generates single photon pulses and transmits the single photon pulses to the intensity modulator, the intensity modulator modulates the average photon number of the single photon pulses and transmits the single photon pulses to the input optical coupler, and the input optical coupler splits the single photon pulses into two paths of sub-optical pulses. One path of sub-optical pulse is output to a first phase modulator of coding phase modulation through an output port of a first optical coupler, is transmitted to one optical fiber of a double-core optical fiber after phase modulation, and is transmitted to an input port of a second optical coupler; and the other path of sub-optical pulse is output to the other optical fiber of the double-core optical fiber through the other output port of the first optical coupler, is transmitted to the second phase modulator for decoding phase modulation, is output to the other input port of the second optical coupler after phase modulation. The second optical coupler combines the two paths of sub-optical pulses and outputs the combined light to the first single-photon detector or the second single-photon detector through the two output ports, and a shared key is generated according to a quantum key distribution protocol. The first phase modulator for encoding phase modulation randomly modulates the phase of 0 degree, 90 degrees, 180 degrees or 270 degrees, and the second phase modulator for decoding phase modulation randomly modulates the phase of 0 degree or 90 degrees.
Example 3:
referring to fig. 3, a phase-encoded quantum key distribution system, comprising: the system comprises 2 single photon sources, 2 intensity modulators, 2 first optical couplers, 2 first phase modulators, a first wavelength division multiplexer, a second wavelength division multiplexer, a multi-core optical fiber, 2 second optical couplers, 2 second phase modulators, a first wavelength division multiplexer, a second wavelength division demultiplexer and 2 first single photon detectors.
The output end of the single photon source to the input end of the first optical coupler form input side branches of the system, and in the embodiment, the number of the input side branches is 2. The output end of the second optical coupler to the input end of the first single-photon detector form output side branches of the system, and in this embodiment, the number of the output side branches is 2. The output end of the first optical coupler forms a systematic quantum channel from the first phase modulator, the multi-core optical fiber and the second phase modulator to the input end of the second optical coupler.
A single photon source is used to generate single photon pulses. One possible configuration of a single photon source is a weakly coherent light source consisting of a pulsed laser that produces pulsed light and an optical attenuator that attenuates the light pulses into single photon pulses.
An intensity modulator is disposed between the single photon source and the first optical coupler for modulating the average photon count of the single photon light pulses.
The first optical coupler comprises at least one input port and two output ports and is used for receiving single photon pulses generated by a single photon source, splitting the single photon pulses generated by the single photon source into two paths of sub-optical pulses and outputting the two paths of sub-optical pulses through the two output ports of the first optical coupler respectively. In this embodiment, the first optical coupler is a 1 × 2 optical coupler.
The multi-core optical fiber is a quantum channel and is used for transmitting two paths of sub-optical pulses output by the two output ports of the first optical coupler. The number of the fiber cores of the multi-core optical fiber is not less than two, one of the fiber cores is connected with one of the two output ports of the first optical coupler and used for transmitting one of the two paths of sub-optical pulses, and the other fiber core is connected with the other of the two output ports of the first optical coupler and used for transmitting the other of the two paths of sub-optical pulses.
The second optical coupler comprises two input ports and at least one output port, wherein one input port of the two input ports of the second optical coupler is connected with one fiber core of the multi-core optical fiber for transmitting one path of sub optical pulse and used for receiving one path of sub optical pulse. And the other input port of the two input ports of the second optical coupler is connected with the other fiber core which transmits the other path of sub optical pulses in the multi-core optical fiber and is used for receiving the other path of sub optical pulses. And one path of sub optical pulse and the other path of sub optical pulse are combined by the second optical coupler and then output by an output port of the second optical coupler. In this embodiment, the second optical coupler is a 2 × 1 optical coupler.
The first single-photon detector is used for detecting the single-photon pulse output by the second optical coupler.
The first phase modulator is used for encoding phase modulation of the quantum key distribution system, and the second phase modulator is used for decoding phase modulation of the quantum key distribution system. The first phase modulator and the second phase modulator are arranged on different optical paths or the same optical path between the output port of the first optical coupler and the input port of the second optical coupler. Taking the example of being arranged on different optical paths, namely: the first phase modulator is arranged on an optical path connecting one output port of the first optical coupler and one fiber core in the multi-core optical fiber. The first phase modulator randomly modulates four phases of 0 degree, 90 th, 180 degree or 270 degree. The second phase modulator is arranged on an optical path connecting the other input port of the second optical coupler with the other fiber core in the multi-core optical fiber. The second phase modulator randomly modulates four phases of 0 degree, 90 th, 180 degree or 270 degree.
The wavelength division multiplexer is used for realizing that a plurality of quantum key distribution system transmitting units multiplex the same quantum channel. The first wavelength division multiplexer is arranged on a light path connecting one output port of the first optical coupler with one fiber core in the multi-core optical fiber; more than two beam splitting ends of the first wavelength division multiplexer are connected with one output port of the first optical coupler of each input side branch, and the beam combining end of the first wavelength division multiplexer is connected with one fiber core in the multi-core optical fiber. The second wavelength division multiplexer is arranged on the light path connecting the other output port of the first optical coupler with the other fiber core in the multi-core optical fiber; more than two beam splitting ends of the second wavelength division multiplexer are connected with the other output port of the first optical coupler of each input side branch, and the beam combining end of the first wavelength division multiplexer is connected with the other fiber core in the multi-core optical fiber. When the first wavelength division multiplexer or the second wavelength division multiplexer and the first phase modulator are located on the same light path between the first optical coupler and the multi-core fiber, the first wavelength division multiplexer or the second wavelength division multiplexer needs to be arranged on one side close to the multi-core fiber.
The wavelength division demultiplexer is used for realizing demultiplexing of a plurality of quantum key distribution system transmitting units to a plurality of quantum key distribution system receiving units after transmission of the same quantum channel. The first wavelength division demultiplexer is arranged on a light path connecting one input port of the second optical coupler with one fiber core in the multi-core optical fiber; the beam combining end of the first wavelength division demultiplexer is connected with one fiber core in the multi-core optical fiber, and more than two beam splitting ends of the first wavelength division demultiplexer are connected with one input port of the second optical coupler of each output side branch. The second wavelength division demultiplexer is arranged on the light path of the other input port of the second optical coupler connected with the other fiber core in the multi-core optical fiber; the beam combining end of the second wavelength division demultiplexer is connected with the other fiber core in the multi-core optical fiber, and more than two beam splitting ends of the second wavelength division demultiplexer are connected with the other input port of the second optical coupler of each output side branch. When the first wavelength division demultiplexer or the second wavelength division demultiplexer and the second phase modulator are located on the same light path between the multi-core fiber and the second optical coupler, the first wavelength division demultiplexer or the second wavelength division demultiplexer needs to be arranged on one side close to the multi-core fiber.
The utility model discloses a realize waiting arm interferometer based on multicore optic fibre and realize phase coding quantum key distribution to solve the problem that waiting arm interferometer phase coding quantum key distribution efficiency is low. Meanwhile, the length control of more than two paths of transmission optical fibers can be realized, and the length difference of more than two paths of transmission optical fibers is kept unchanged when the transmission optical fibers are interfered by the environment.
It should be noted that, although the above-mentioned embodiments of the present invention are illustrative, the present invention is not limited thereto, and therefore, the present invention is not limited to the above-mentioned embodiments. Other embodiments, which can be made by those skilled in the art in light of the teachings of the present invention, are considered to be within the scope of the present invention without departing from the principles thereof.
Claims (9)
1. A phase-encoded quantum key distribution system, comprising: the single-photon detector comprises a single-photon source, a first optical coupler, a first phase modulator, a multi-core fiber, a second optical coupler, a second phase modulator and one or two single-photon detectors;
the single photon source is used for generating single photon pulses;
the first optical coupler comprises at least one input port and two output ports, and is used for receiving single photon pulses generated by a single photon source, splitting the single photon pulses generated by the single photon source into two paths of sub-optical pulses, and outputting the two paths of sub-optical pulses through the two output ports of the first optical coupler respectively;
the multi-core optical fiber is a quantum channel and is used for transmitting two paths of sub-optical pulses output by two output ports of the first optical coupler; the number of the fiber cores of the multi-core optical fiber is not less than two, one of the fiber cores is connected with one of the two output ports of the first optical coupler and used for transmitting one of the two paths of sub-optical pulses, and the other fiber core is connected with the other of the two output ports of the first optical coupler and used for transmitting the other of the two paths of sub-optical pulses;
the second optical coupler comprises two input ports and at least one output port, wherein one input port of the two input ports of the second optical coupler is connected with one fiber core which transmits one path of sub optical pulse in the multi-core optical fiber and is used for receiving one path of sub optical pulse; the other input port of the two input ports of the second optical coupler is connected with the other fiber core which transmits the other path of sub optical pulse in the multi-core optical fiber and is used for receiving the other path of sub optical pulse; one path of sub optical pulse and the other path of sub optical pulse are output by one or two output ports of the second optical coupler after being combined by the second optical coupler;
the single-photon detector is used for detecting the single-photon pulse output by the output port of the second optical coupler;
the first phase modulator is arranged on an optical path connecting one output port of the first optical coupler with one fiber core in the multi-core optical fiber or on an optical path connecting the other output port of the first optical coupler with the other fiber core in the multi-core optical fiber; the first phase modulator is used for encoding phase modulation of a quantum key distribution system;
the second phase modulator is arranged on an optical path where one input port of the second optical coupler is connected with one fiber core in the multi-core optical fiber, or is arranged on an optical path where the other input port of the second optical coupler is connected with the other fiber core in the multi-core optical fiber; the second phase modulator is used for decoding phase modulation of the quantum key distribution system.
2. The phase-coded quantum key distribution system of claim 1, wherein when there is one single photon detector, the first phase modulator randomly modulates four phases of 0 degree, 90 th, 180 degree or 270 degree; the second phase modulator randomly modulates four phases of 0 degree, 90 th, 180 degree or 270 degree.
3. The phase-coded quantum key distribution system of claim 1, wherein when there are two single photon detectors, the first phase modulator randomly modulates four phases of 0 degree, 90 th, 180 degree or 270 degree; the second phase modulator randomly modulates two phases of 0 degree or 90 degrees.
4. A phase-coded quantum key distribution system as claimed in claim 1, wherein the single photon source is a weak coherent light source and is comprised of a pulsed laser and an optical attenuator; the pulse laser generates pulse light, and the attenuator attenuates the pulse light into single photon pulses.
5. A phase encoded quantum key distribution system according to claim 1, further comprising an intensity modulator; the intensity modulator is arranged on a light path between the single photon source and the first optical coupler and used for modulating the average photon number of the single photon light pulse.
6. A phase encoded quantum key distribution system according to claim 1, further comprising a polarization controller;
the polarization controller is arranged on a light path connecting one output port of the first optical coupler with one fiber core in the multi-core optical fiber or arranged on a light path connecting the other output port of the first optical coupler with the other fiber core in the multi-core optical fiber; or on the optical path where one input port of the second optical coupler is connected to one core of the multicore fiber, or on the optical path where the other input port of the second optical coupler is connected to the other core of the multicore fiber.
7. A phase encoded quantum key distribution system according to claim 1,
an input side branch of the system is formed from an output end of the single photon source to an input port of the first optical coupler; an output port of the second optical coupler to an input end of the first single-photon detector form an output side branch of the system; an output port of the first optical coupler forms a quantum channel of the system through the first phase modulator, the multi-core optical fiber and the second phase modulator to an input port of the second optical coupler; wherein the number of the input side branches and the output side branches is more than 2.
8. A phase encoded quantum key distribution system according to claim 7, further comprising a first wavelength division multiplexer and/or a second wavelength division multiplexer;
the first wavelength division multiplexer is arranged on a light path connecting one output port of the first optical coupler with one fiber core in the multi-core optical fiber; more than two beam splitting ends of the first wavelength division multiplexer are connected with one output port of the first optical coupler of each input side branch, and the beam combining end of the first wavelength division multiplexer is connected with one fiber core in the multi-core optical fiber;
the second wavelength division multiplexer is arranged on the light path connecting the other output port of the first optical coupler with the other fiber core in the multi-core optical fiber; more than two beam splitting ends of the second wavelength division multiplexer are connected with the other output port of the first optical coupler of each input side branch, and the beam combining end of the first wavelength division multiplexer is connected with the other fiber core in the multi-core optical fiber.
9. A phase encoded quantum key distribution system according to claim 7, further comprising a first wavelength division demultiplexer and/or a second wavelength division demultiplexer;
the first wavelength division demultiplexer is arranged on a light path connecting one input port of the second optical coupler with one fiber core in the multi-core optical fiber; the beam combining end of the first wavelength division demultiplexer is connected with one fiber core in the multi-core optical fiber, and more than two beam splitting ends of the first wavelength division demultiplexer are connected with one input port of the second optical coupler of each output side branch;
the second wavelength division demultiplexer is arranged on the light path of the other input port of the second optical coupler connected with the other fiber core in the multi-core optical fiber; the beam combining end of the first wavelength division demultiplexer is connected with the other fiber core in the multi-core optical fiber, and more than two beam splitting ends of the second wavelength division demultiplexer are connected with the other input port of the second optical coupler of each output side branch.
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