CN107566043B

CN107566043B - A kind of quantum key transmitting terminal, receiving end, system and method

Info

Publication number: CN107566043B
Application number: CN201710854218.7A
Authority: CN
Inventors: 沈方红; 陈建; 穆道生
Original assignee: Beijing Sino Quantum Communication Technology Co Ltd
Current assignee: Beijing Sino Quantum Communication Technology Co Ltd
Priority date: 2017-09-15
Filing date: 2017-09-15
Publication date: 2019-07-12
Anticipated expiration: 2037-09-15
Also published as: CN107566043A

Abstract

The present invention provides a kind of quantum key transmitting terminals, receiving end, system and method, the quantum key transmitting terminal includes: main laser, first from laser, second from laser, synchronous laser, unequal arm interferometer, first annular device, second circulator, first beam splitter, filter, attenuator, wavelength division multiplexer, wherein, main laser connects unequal arm interferometer, one end of unequal arm interferometer connects the first port of first annular device, the other end of unequal arm interferometer connects the first port of the second circulator, the second port of first annular device connects first from laser, the third port of first annular device connects the reflection end of the first beam splitter, second circulator second port connects second from laser, the third port of second circulator connects the transmission end of the first beam splitter, first beam splitter connects filter, Filter connects attenuator, and attenuator connects the transmission end of wavelength division multiplexer, and synchronous laser connects the reflection end of wavelength division multiplexer.

Description

Quantum key sending end, quantum key receiving end, quantum key sending system and quantum key receiving system

Technical Field

The invention relates to the technical field of quantum secret communication, in particular to a quantum key sending end, a quantum key receiving end, a quantum key distribution system and a quantum key distribution method.

Background

With the deep development of the internet, the information security faces more and more challenges. At present, quantum key distribution systems of BB84 protocol are widely used, and encoding methods of the quantum key distribution systems are phase encoding, time phase encoding, polarization encoding, and the like. The transmitting end and the receiving end of the quantum key distribution system based on polarization coding can easily realize the calibration of a polarization reference system. Therefore, the quantum key distribution system based on polarization encoding can be applied to large-scale networked quantum secret communication networks. However, polarization encoding is relatively weak in polarization disturbance immunity to a long-distance channel, and particularly in scenes such as an aerial optical cable with large wind power and an underground optical cable with large vibration, so that a quantum key distribution system based on polarization encoding cannot normally operate at a long distance.

The quantum key distribution system based on phase coding or time phase coding needs a pair of unequal arm interferometers with matched lengths at a sending end and a receiving end to realize phase interference. Currently, an unequal arm interferometer is usually prepared by using an optical fiber or a planar optical waveguide, but since the optical path length of the optical fiber and the planar optical waveguide changes constantly under the influence of various factors and the micrometer-scale measurement accuracy is quite complex and difficult, the preparation of a plurality of unequal arm interferometers with matched lengths based on the optical fiber or the planar optical waveguide has been a challenge. Therefore, the quantum key distribution system based on the phase coding or the time phase coding is difficult to perform the networking deployment of the large-scale quantum secret communication.

Therefore, how to implement the problem of matching the lengths of the multiple unequal-arm interferometers is a technical problem which needs to be solved urgently by those skilled in the art at present.

Disclosure of Invention

The technical problem to be solved by the embodiments of the present invention is to provide a transmitting end, a receiving end and a system for quantum keys, so as to solve the problem that the length matching of multiple unequal-arm interferometers cannot be realized in the prior art.

Correspondingly, the embodiment of the invention also provides a sending method of the quantum key and a receiving and sending method of the quantum key, which are used for ensuring the realization and the application of the equipment.

In order to solve the above problems, the present invention discloses a quantum key transmitting end, which includes: a master laser, a first slave laser, a second slave laser, a synchronous laser, an unequal arm interferometer, a first circulator, a second circulator, a first beam splitter, a filter, an attenuator and a wavelength division multiplexer, wherein the master laser is connected with the unequal arm interferometer, one end of the unequal arm interferometer is connected with a first port of the first circulator, the other end of the unequal arm interferometer is connected with a first port of the second circulator, a second port of the first circulator is connected with the first slave laser, a third port of the first circulator is connected with a reflection end of the first beam splitter, a second port of the second circulator is connected with the second slave laser, a third port of the second circulator is connected with a transmission end of the first beam splitter, the first beam splitter is connected with the filter, and the filter is connected with the attenuator, the attenuator is connected with the transmission end of the wavelength division multiplexer, and the synchronous laser is connected with the reflection end of the wavelength division multiplexer; the unequal arm interferometer divides a main laser pulse emitted by the main laser into two same main laser pulses in time, and the two same main laser pulses are respectively injection-locked to the first slave laser and the second slave laser to generate slave laser pulses; when the master laser pulse is injected, voltages with different intensities are triggered to the first slave laser and the second slave laser, so that the first slave laser and the second slave laser emit slave laser pulses with different intensities, the slave laser pulses are input to a first beam splitter, the first beam splitter adjusts and codes the received slave laser pulses with different intensities to obtain quantum signal light, and the quantum signal light passes through a filter and an attenuator and is emitted after passing through a wavelength division multiplexer together with a classical synchronous light signal generated by a synchronous laser.

Optionally, the interferometer with unequal arms includes: the transmission end of the first beam splitter is connected with the transmission end of the second beam splitter, and the reflection end of the first beam splitter is connected with the reflection end of the second beam splitter; the first beam splitter is further connected with the main laser, and the second beam splitter is further connected with the first circulator and the second circulator respectively.

Optionally, the sending end further includes: first 90 degrees Faraday rotator, second 90 degrees Faraday rotator and third circulator, wherein, the first port of third circulator is connected with main laser, the second port of third circulator is connected the one end of inequality arm interferometer, the other end of inequality arm interferometer is connected second 90 degrees Faraday rotator, the third port of third circulator is connected first 90 degrees Faraday rotator, first 90 degrees Faraday rotator is connected the first port of first circulator.

Optionally, the interferometer with unequal arms includes: the beam splitter comprises a fourth beam splitter, a first 90-degree Faraday reflector and a second 90-degree Faraday reflector; and the fourth beam splitter is respectively connected with the second port of the third circulator, the first 90-degree Faraday reflector, the second 90-degree Faraday reflector and the second 90-degree Faraday rotator.

Optionally, the first ports of the first circulator, the second circulator and the third circulator are inlets of optical signals, and the second port is an outlet of an optical signal; or the second port is an inlet of the optical signal, and the third port is an outlet of the optical signal.

Optionally, the phase of the main laser pulse sent by the main laser is a randomized phase, and the randomized phase is modulated by using a decoy method.

Optionally, the decoy state method modulation includes:

generating optical pulses with different intensities for internal driving voltage or current different amplitude signals of the first slave laser and the second slave laser; or

The external intensity modulator is used for modulating the intensity of the light pulse; or

The external phase modulator is combined with a self-interference principle to generate light pulses with different intensities; or

Multiple slave lasers are used in conjunction with fixed attenuators or different proportional beam splitters to produce different intensity light pulses.

Optionally, the common end of the wavelength division multiplexer is configured to transmit the quantum signal light and the classical synchronization light at the same time, where the transmission end of the wavelength division multiplexer transmits the quantum signal light, and the reflection end of the wavelength division multiplexer transmits the classical synchronization light.

In a second aspect, an embodiment of the present invention further provides a receiving end of a quantum key, including:

the device comprises a wavelength division multiplexer, a synchronous optical detector, a first beam splitter, a first single photon detector, a circulator, a second beam splitter, a phase shifter, a first 90-degree Faraday reflector, a second single photon detector and a third single photon detector, wherein a reflection end of the wavelength division multiplexer is connected with the synchronous optical detector, a transmission end of the wavelength division multiplexer is connected with the first beam splitter, a reflection end of the first beam splitter is connected with the first single photon detector, a transmission end of the first beam splitter is connected with a first port of the circulator, a third port of the circulator is connected with the second single photon detector, a second port of the circulator is connected with one end of the unequal arm interferometer, and the other end of the unequal arm interferometer is connected with the third single photon detector, the wavelength division multiplexer demultiplexes received quantum signal light and classical synchronous light to obtain synchronous light, the synchronous light detector detects synchronous signals to achieve system synchronization of a sending end and a receiving end, the quantum signal light performs passive basis vector selection, Z basis vector time bit measurement and X basis vector phase bit measurement through the beam splitter, the single-photon detector performs Z basis vector time bit measurement, the second single-photon detector and the third single-photon detector perform X basis vector phase bit measurement, phase shifter voltage is fed back in real time according to the error rate of the system at X basis vectors, and phase reference systems of the receiving end and the sending end are adjusted.

Optionally, the interferometer with unequal arms includes: the phase shifter comprises a second beam splitter, a phase shifter, a first 90-degree Faraday reflector and a second 90-degree Faraday reflector, wherein the beam splitter is respectively connected with a second port of the circulator, the second 90-degree Faraday reflector, the phase shifter and a third single photon detector, and the phase shifter is also connected with the first 90-degree Faraday reflector.

In a third aspect, an embodiment of the present invention further provides a system for transmitting and receiving a quantum key, where the system includes: a sending end of the quantum key, a receiving end of the quantum key, and a quantum channel or circulator, wherein the sending end of the sub-key and the receiving end of the sub-key are connected through the quantum channel or circulator,

the quantum key sending terminal is the quantum key sending terminal;

the receiving end of the quantum key is the receiving end of the quantum key.

In a fourth aspect, an embodiment of the present invention further provides a method for sending a quantum key, where the method includes:

triggering to generate a main laser pulse;

temporally dividing the main laser pulse into two identical main laser pulses;

respectively injecting and locking the two same main laser pulses, and controlling the two same main laser pulses through voltages with different intensities to generate slave laser pulses with different intensities;

modulating and coding the slave laser pulses with different intensities to obtain quantum signal light;

filtering and attenuating the quantum signal light to obtain quantum signal light with a single photon level;

and transmitting the quantum signal light of the single photon level and the generated classical synchronous signal to a receiving end after wavelength division multiplexing.

Optionally, the phase of the main laser pulse is a randomized phase, and the randomized phase is modulated by using a decoy method.

Optionally, the decoy state method modulation includes:

generating light pulses with different intensities by internal driving voltage or current signals with different amplitudes; or

An external intensity modulator is used for modulating the intensity of the light pulse; or

In a fifth aspect, an embodiment of the present invention further provides a quantum key transceiving method based on a quantum key transceiving system, including:

triggering and generating a main laser pulse by a sending end;

the main laser pulse of the sending end is divided into two same main laser pulses in time;

the sending end respectively controls the voltage of the two same main laser pulses with different intensities to generate slave laser pulses with different intensities;

the transmitting end modulates and codes the slave laser pulses with different intensities to obtain quantum signal light;

the sending end filters and attenuates the quantum signal light to obtain the quantum signal light with single photon level;

the transmitting end transmits the quantum signal light of the single photon level and the generated classical synchronous signal to a receiving end through a quantum channel after wavelength division multiplexing;

the receiving end demultiplexes the quantum signal light of the single photon level received through the quantum channel and the generated classical synchronous signal to obtain a classical synchronous signal and quantum signal light;

the receiving end carries out passive basis vector selection, Z basis vector time bit measurement and X basis vector phase bit measurement on the quantum signal light, and determines the error rate of X basis vectors;

and the receiving end adjusts the phase reference coefficient of the receiving end and the transmitting end according to the error rate of the X basis vector.

Optionally, the control method for respectively performing voltage control on the two same main laser pulses with different intensities includes:

Multiple pulses of light of different intensities are generated from a laser in combination with a fixed attenuator or a different proportional beam splitter.

Compared with the prior art, the embodiment of the invention has the following advantages:

the embodiment of the invention provides a quantum key sending end, a quantum key receiving and sending system and a quantum key receiving and sending method, which can control the phase coding of a main laser pulse, utilize the quantum properties of a beam splitter to passively encode different phase bits, and utilize the pulse laser injection technology to realize the optical phase randomness of a signal pulse prepared from a laser, overcome the defects of the existing time phase coding scheme, realize a simple and high-speed quantum key distribution system, and further solve the problem of unequal arm interferometer length matching in large-scale networked deployment.

Drawings

Fig. 1 is a schematic structural diagram of a transmitting end of a quantum key according to an embodiment of the present invention;

fig. 2 is another schematic structural diagram of a quantum key transmitting end according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of an embodiment of the present invention for generating time bit encoded pulses and phase bit encoded pulses by injection locking;

FIG. 4(a) is a schematic diagram of the quantum nature of a beam splitter provided by an embodiment of the present invention;

FIG. 4(b) is a schematic diagram of quantum state change of a coherent light source after passing through a beam splitter according to an embodiment of the present invention;

fig. 5 is another schematic structural diagram of a quantum key transmitting end according to an embodiment of the present invention;

FIG. 6 is a schematic structural diagram of FIG. 5 according to an embodiment of the present invention;

fig. 7 is a schematic structural diagram of a quantum key receiving end according to an embodiment of the present invention;

fig. 8 is a schematic structural diagram of a quantum key transceiving system according to an embodiment of the present invention;

fig. 9 is a schematic structural diagram of a first application example of a quantum key distribution system according to an embodiment of the present invention;

fig. 10 is a schematic structural diagram of a second application example of a quantum key distribution system according to an embodiment of the present invention;

fig. 11 is a schematic structural diagram of a third application example of a quantum key distribution system according to an embodiment of the present invention;

fig. 12 is a flowchart of a quantum key sending method according to an embodiment of the present invention;

fig. 13 is another flowchart of a quantum key sending method according to an embodiment of the present invention.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

Referring to fig. 1, a structural diagram of a quantum key transmitting end provided in an embodiment of the present invention is shown, where the quantum key transmitting end includes:

a master laser 1-1, a first slave laser 1-2, a second slave laser 1-3, a synchronous laser 1-4, an unequal arm interferometer 1-25, a first circulator 1-7, a second circulator 1-8, a first beam splitter 1-9, a filter 1-10, an attenuator 1-11, a wavelength division multiplexer 1-12, wherein the master laser 1-1 is connected with the unequal arm interferometer 1-25, one end of the unequal arm interferometer 1-25 is connected with a first port of the first circulator 1-7, the other end of the unequal arm interferometer 1-25 is connected with a first port of the second circulator 1-8, a second port of the first circulator 1-7 is connected with the first slave laser 1-2, and a third port of the first circulator 1-2 is connected with a reflection port of the third beam splitter 1-9 And a second port of the second circulator 1-8 is connected with the second slave laser 1-3, a third port of the second circulator 1-8 is connected with a transmission end of the first beam splitter 1-9, the first beam splitter 1-9 is connected with the filter 1-10, the filter 1-10 is connected with the attenuator 1-11, the attenuator 1-11 is connected with a transmission end of the wavelength division multiplexer 1-12, and the synchronous laser 1-4 is connected with a reflection end of the wavelength division multiplexer 1-12.

In the embodiment, the unequal arm interferometer 1-25 divides a main laser pulse emitted by the main laser 1-1 into two same main laser pulses in time, and injection-locks the two main laser pulses to the first slave laser 1-2 and the second slave laser 1-3 to generate a slave laser pulse respectively; when a master laser pulse is injected, different voltages are triggered to the first slave laser 1-2 and the second slave laser 1-3, so that the first slave laser and the second slave laser emit slave laser pulses with different intensities, the slave laser pulses are input to the first beam splitter 1-9, the first beam splitter 1-9 adjusts and codes the received slave laser pulses with different intensities to obtain quantum signal light, the quantum signal light passes through the filter 1-10 and the attenuator 1-11, and the quantum signal light and the classical synchronous light output by the synchronous laser 1-4 are emitted after passing through the wavelength division multiplexer 1-12.

Optionally, in this embodiment, the first port of the first circulator and/or the second port of the second circulator is an inlet of an optical signal, and the second port is an outlet of the optical signal; or the second port is an inlet of the optical signal, and the third port is an outlet of the optical signal.

Optionally, on the basis of the embodiment in fig. 1, the unequal-arm interferometers 1-25 include: fig. 2 is a schematic structural diagram of a second splitter 1-6 and a third splitter 1-5, and fig. 2 is another schematic structural diagram of a quantum key transmitting end according to an embodiment of the present invention, wherein,

the transmission end of the first beam splitter 1-9 is connected with the transmission end of the second beam splitter 1-6, and the reflection end of the first beam splitter 1-9 is connected with the reflection end of the second beam splitter 1-6; the first beam splitter 1-9 is further connected with the main laser 1-1, and the second beam splitter 1-6 is further connected with the first circulator 1-7 and the second circulator 1-8 respectively.

In the above embodiment, the main laser 1-1 emits a main laser pulse with randomized phase (taking a wide pulse light as an example compared with the present embodiment) and forms two identical main laser pulses (i.e. wide pulse light) by the unequal-arm interferometer 1-25 at the transmitting end as shown in fig. 3, where fig. 3 is a schematic diagram of injection-locked generation of a time-bit coded pulse and a phase-bit coded pulse according to an embodiment of the present invention.

As shown in fig. 3, two identical wide pulses are injected into the first slave laser 1-2 and the second slave laser 1-3. During the time corresponding to the injection of the wide pulse, the transmitting end sends the first slave laser 1-2 (taking the first slave laser as an example, to the second slave laser) through the electronic system according to the random number settingThe same as the optical process) triggers different voltages to allow the first slave laser 1-2 to injection-lock emit slave laser pulses of different intensities. Thus, the first slave laser 1-2 can emit a single narrow pulse before or after, i.e. encoding the Z-basis vector time bits; two narrow pulses before and after can be transmitted simultaneously, namely X-base vector phase bit encoding. Due to the property of injection locking, the frequency and the phase of the first slave laser 1-2 are the same as those of the master laser pulse during injection locking, and due to the fact that the phase and the frequency in one pulse are almost the same, the frequencies of the front slave laser pulse and the rear slave laser pulse are almost the same, then the polarization consistency of the front slave laser pulse and the rear slave laser pulse is ensured by using a polarization-maintaining jumper wire, and the time domain shapes of the modulated electric signals are approximately consistent. That is, two identical master laser pulses are derived from the same master laser pulse (e.g., a wide pulse), and the intrinsic phases of the two master laser pulses are identical when injected into the first slave laser and the second slave laser pulse. The phase of propagation is caused by the unequal arm interferometer at the transmitting end, so that the two wide pulses are out of phase, i.e.With a time interval of time difference T1 for the unequal-arm interferometer. The phase difference between the two preceding and succeeding slave laser pulses being equal to the phase difference between the two master laser pulses at the time of injection, i.e. the phase difference between the two master laser pulses at the time of injection

Alternatively, the unequal arm interferometers 1-25 in the above embodiments may be Mach Zehnder unequal arm interferometers or Mach Zehnder unequal arm interferometers.

The probability of modulating various intensities by the time or phase bit coding and decoy state method is arbitrary, and an approximate optimal value can be obtained by utilizing an optimization algorithm according to different parameter conditions.

The first single-photon detector is used for detecting Z-basis vector time bit decoding, and Z-basis vector time bit values can also be detected by replacing the first single-photon detector with a beam splitter and two single-photon detectors respectively.

The wavelength division multiplexer is characterized in that a public end of the wavelength division multiplexer transmits quantum signal light and classical synchronous light at the same time, a transmission end of the wavelength division multiplexer transmits the quantum signal light, and a reflection end of the wavelength division multiplexer transmits the classical synchronous light.

The 90-degree Faraday mirror reflects the optical signal back to the starting point of propagation, and the polarization of the optical signal is just rotated by 90 degrees, so that the birefringence effect of the optical fiber is immunized.

Wherein the 90 degree Faraday rotator rotates the polarization of the optical signal by 90 degrees.

The filter removes the spontaneous radiation noise from the laser, increases the extinction ratio of time bit coding and phase bit coding to reduce the error rate of the system, and can be a Fiber Bragg Grating (FBG), a Dense Wavelength Division Multiplexer (DWDM) and the like.

Wherein, the slave laser is internally provided with no optical isolator, so that the slave laser pulse can be generated by injecting external light into the slave laser to lock.

Wherein, the master laser and the slave laser can be internally integrated with a package filter for reducing the spontaneous radiation noise.

In the embodiment of the present invention, in order to achieve stable interference of the system, it is necessary to compensate the phase change in the unequal-arm interferometer at the receiving end, for example, the phase change may be compensated by adjusting the phase shifter. The time interval T2 between the two previous slave laser pulses is determined by the voltage signal given to the light emission of the first slave laser 1-2 and the second slave laser 1-3, and therefore the interval is controlled with electronic precision, rather than by the arm length difference of the unequal arm interferometers 1-25 at the transmitting end. Therefore, the precision of the time difference T1 of the unequal arm interferometers 1-25 of the sending end can be relaxed, and the preparation of the lengths of a plurality of sets of the unequal arm interferometers of the sending end is facilitated.

Referring to fig. 4(a) and fig. 4(b), which are schematic diagrams of quantum properties of a beam splitter and quantum state changes of a coherent light source after passing through the beam splitter according to an embodiment of the present invention:

as shown in fig. 4(a), a quantum representation diagram of a four-port beam splitter, where a and b are annihilation operators in quantum mechanics. Thus, for the coherent light source, two paths of front and back light pulses output by the beam splitter, wherein one path has no phase change to 0 phase code, and the other path has pi phase change to pi phase code, as shown in fig. 4 (b). The quantum state evolution of the coherent state after passing through the beam splitter is shown in fig. 4(b), and the preparation of the 0 phase and the pi phase is visually presented. According to the random number setting, if the first slave laser 1-2 performs 0 phase coding on the two slave laser pulses before and after reflection, the second slave laser 1-3 transmits the two pulses before and after to perform pi phase coding. The optical pulse with different intensities emitted from the voltage signals with different amplitudes of the laser can be modulated by a trap state method according to the random number setting, or the optical pulse is modulated by the trap state method by an external intensity modulator or a phase modulator for realizing the intensity modulation function. The slave laser pulses emitted from the laser 1-2 and the slave laser pulses emitted from the laser 1-3 are combined by the beam splitter 1-9 to adjust temporal consistency thereof. The modulated and coded quantum signal light passes through a filter 1-10 to remove spontaneous emission noise, then passes through an attenuator 1-11 to attenuate the quantum signal light with the intensity reaching the single photon level, and then is transmitted to a receiving end through a wavelength division multiplexer 1-12 and a quantum channel 1-13 together with a classical synchronous optical signal which is generated from a synchronous laser 1-4 and used for calibrating the time sequence of a transmitting end and a receiving end.

The embodiment of the invention provides a sending end of a quantum key, which can control the strength of the phase code of a main laser pulse, passively encode different phase bits by utilizing the quantum property of a beam splitter, realize the optical phase randomness of a signal pulse prepared by a slave laser by utilizing a pulse laser injection technology, overcome the defects of the existing time phase encoding scheme, realize a simple and high-speed quantum key distribution system and further solve the problem of length matching of an unequal-arm interferometer in large-scale networked deployment.

Optionally, on the basis of the embodiment in fig. 1, the quantum key sending end may further include: a schematic structural diagram of the first 90-degree faraday rotator 2-9, the second 90-degree faraday rotator 2-11, and the third circulator 2-5 is shown in fig. 5, and fig. 5 is another schematic structural diagram of a quantum key transmitting end according to an embodiment of the present invention. Wherein,

the first port of the third circulator 2-5 is connected with the main laser 1-1, the second port of the third circulator 2-5 is connected with one end of the unequal arm interferometer 1-25, the other end of the unequal arm interferometer 1-25 is connected with the second 90-degree Faraday rotator 2-11, the third port of the third circulator 2-5 is connected with the first 90-degree Faraday rotator 2-9, and the first 90-degree Faraday rotator 2-9 is connected with the first port of the first circulator 2-10.

Optionally, on the basis of the embodiment shown in fig. 5, the unequal-arm interferometers 1-25 comprise: a fourth beam splitter 2-6, a first 90-degree Faraday reflector 2-7 and a second 90-degree Faraday reflector 2-8; the unequal-arm interferometer in this embodiment is a michelson unequal-arm interferometer or a michelson unequal-arm interferometer. The fourth beam splitter is respectively connected with the second port of the third circulator 2-5, the first 90-degree faraday reflector 2-7, the second 90-degree faraday reflector 2-8 and the second 90-degree faraday rotator 2-11. The specific structure diagram is shown in detail in fig. 6, and fig. 6 is the specific structure diagram of fig. 5.

The quantum key transmitting terminal comprises: a master laser 1-1, a first slave laser 1-2, a second slave laser 1-3, a synchronous laser 1-4, a third circulator 2-5, a fourth beam splitter 2-6, a first 90-degree Faraday mirror 2-7, a second 90-degree Faraday mirror 2-8, a first 90-degree Faraday rotator 2-9, a second circulator 1-8, a second 90-degree Faraday rotator 2-11, a first circulator 1-7, a first beam splitter 1-9, a filter 1-10, an attenuator 1-11, and a wavelength division multiplexer 1-12, wherein the master laser 1-1 is connected with a first port of the third circulator 2-5, a second port of the third circulator 2-5 is connected with one end of the Michelson arm unequal interferometer, the other end of the Michelson unequal-arm interferometer is connected with the second 90-degree Faraday rotator 2-11, the third port of the third circulator 2-5 is connected with the first 90-degree Faraday rotator 2-9, the first 90-degree Faraday rotator 2-9 is connected with the first port of the second circulator 1-8, the second port of the first circulator 1-7 is connected with the first slave laser 1-2, the third port of the first circulator 1-7 is connected with the reflection end of the first beam splitter 1-9, the second port of the second circulator 1-8 is connected with the second slave laser 1-3, the third port of the second circulator 1-8 is connected with the transmission end of the first beam splitter 1-9, and the first beam splitter 1-9 is connected with the filter 1-10, The filter 1-10 is connected with the attenuator 1-11, the attenuator 1-11 is connected with the transmission end of the wavelength division multiplexer 1-12, and the synchronous laser 1-4 is connected with the reflection end of the wavelength division multiplexer 1-12, so that the public end of the wavelength division multiplexer at the receiving end is connected with the public end of the wavelength division multiplexer 1-12 at the transmitting end through a quantum channel.

Optionally, in this embodiment, the first ports of the first circulator, the second circulator and the third circulator are inlets of optical signals, and the second port is an outlet of an optical signal; or the second port is an inlet of the optical signal, and the third port is an outlet of the optical signal.

Optionally, in this embodiment, a phase of a main laser pulse sent by the main laser is a randomized phase, and the randomized phase is modulated by using a decoy method. Wherein, the decoy state method modulation comprises: generating optical pulses with different intensities for internal driving voltage or current different amplitude signals of the first slave laser and the second slave laser; or the external intensity modulator is used for modulating the intensity of the light pulse; or the external phase modulator is combined with the self-interference principle to generate light pulses with different intensities; or multiple pulses of light of different intensities generated from a laser in combination with a fixed attenuator or a different proportional beam splitter.

Optionally, in this embodiment, the common end of the wavelength division multiplexer is configured to transmit the quantum signal light and the classical synchronization light simultaneously, where the transmission end of the wavelength division multiplexer transmits the quantum signal light and the reflection end of the wavelength division multiplexer transmits the classical synchronization light.

The specific implementation process in this embodiment is similar to that in the above embodiment, and specific details are not described herein again.

Referring to fig. 7, fig. 7 is a schematic structural diagram of a quantum key receiving end according to an embodiment of the present invention, including:

the device comprises a wavelength division multiplexer 1-14, a synchronous optical detector 1-15, a first beam splitter 1-16, a first single-photon detector 1-17, a circulator 1-18, a second beam splitter 1-19, a phase shifter 1-20, a first 90-degree Faraday mirror 1-21, a second 90-degree Faraday mirror 1-22, a second single-photon detector 1-23 and a third single-photon detector 1-24, wherein the second beam splitter 1-19 and an unequal-arm interferometer are arranged on the same plane, the reflection end of the wavelength division multiplexer 1-14 is connected with the synchronous optical detector 1-15, the transmission end of the wavelength division multiplexer 1-14 is connected with the first beam splitter 1-16, the reflection end of the first beam splitter 1-16 is connected with the first single-photon detector 1-17, the transmission end of the first beam splitter is connected with a first port of the circulator 1-18, the third port of the circulator 1-18 is connected with the second single-photon detector 1-23, the second port of the circulator is connected with one end of the unequal arm interferometer, the other end of the unequal arm interferometer is connected with the third single-photon detector 1-24, wherein the wavelength division multiplexer 1-14 demultiplexes the received quantum signal light and the classical synchronous light to obtain synchronous light, the synchronous light detector 1-15 detects synchronous signals to realize system synchronization of a transmitting end and a receiving end, the quantum signal light carries out passive basis vector selection, Z basis vector time bit measurement and X basis vector phase bit measurement through the beam splitter 1-16, the single-photon detector 1-17 carries out Z basis vector time bit measurement, and the single-photon detectors 1-23 and 1-24 carry out X basis vector phase bit measurement, and feeding back the voltage of the phase shifter in real time according to the error rate of the system in the X basis vector, and adjusting the phase reference system of the receiving end and the transmitting end.

That is, the receiving end demultiplexes by the wavelength division multiplexers 1-14 to obtain the synchronous light, and the synchronous light detectors 1-15 are used for detecting the synchronous signals to realize the system synchronization of the transmitting end and the receiving end. The quantum signal light is subjected to passive basis vector selection through the beam splitters 1-16 to perform Z basis vector time bit measurement and X basis vector phase bit measurement, the selection probability is arbitrary, and optimal selection can be achieved. The single-photon detectors 1-17 perform Z-basis vector time bit measurement, and the single-photon detectors 1-23 and 1-24 perform X-basis vector phase bit measurement. And feeding back the voltage of the phase shifter in real time according to the error rate of the system in the X basis vector, and adjusting the phase reference system of the receiving end and the transmitting end. To relax the performance requirements of the single photon detectors 1-17, one of the detectors can be adapted to externally connect two single photon detectors with one detector time bit 0 and the other detecting time bit 1.

Referring to fig. 8, fig. 8 is a schematic structural diagram of a transmitting and receiving system for quantum keys according to an embodiment of the present invention, where the transmitting and receiving system includes: a quantum key sending end 8-1, a quantum key receiving end 8-2 and a quantum channel 8-3, wherein the sending end of the sub-key and the receiving end of the sub-key are connected through the quantum channel or the circulator,

wherein the quantum channel is a single mode fiber or a free space.

Optionally, in another embodiment, the quantum key sending end and the quantum key receiving end may be further integrated together through a circulator.

The description of the structures and functions of the quantum key sending end and the quantum key receiving end is detailed in the above corresponding embodiments, and is not repeated here.

The technical scheme of the invention has the advantages that the error rate of the system is not influenced by the channel polarization drift, the time bit coding is easy to realize and has high contrast, the time interval of the phase coding pulse of the sending end is controlled by electronics, the matching of a plurality of sending ends and one receiving end can be realized, and the large-scale networked deployment is facilitated. The quantum property of the beam splitter is used for passively realizing the phase bit coding of 0 and 180 degrees, the pulse laser injection technology is used for realizing the random phase of the signal pulse light prepared from the laser, the spectral line width and the time jitter are simultaneously narrowed to improve the interference contrast, and the time difference of pulse phase interference realized by the transmitting end and the receiving end is relaxed. The quantum key distribution system is simple in structure and easy to integrate.

Referring to fig. 9, a first application example of a quantum key distribution system according to an embodiment of the present invention is a quantum key distribution system encoded by a time phase BB84 for easy networking, as shown in fig. 9, including a transmitting end 91, a receiving end 92, and quantum channels 1 to 13, where the transmitting end 91 and the receiving end 92 are connected through the quantum channels 1 to 13. Wherein,

the transmitting end 91 comprises a master laser 1-1, a first slave laser 1-2, a second slave laser 1-3, a synchronous laser 1-4, a third beam splitter 1-5, a second beam splitter 1-6, a first circulator 1-7, a second circulator 1-8, a first beam splitter 1-9, a filter 1-10, an attenuator 1-11 and a wavelength division multiplexer 1-12, wherein the third beam splitter 1-5, the second beam splitter 1-6 and optical fibers connected with the third beam splitter form a Mach-Zehnder unequal arm interferometer at the transmitting end, the master laser 1-1 is connected with the Mach-Zehnder unequal arm interferometer at the transmitting end, one end of the Mach-Zehnder unequal arm interferometer at the transmitting end is connected with a first port of the first circulator 1-7, the other end of the sending-end Mach-Zehnder unequal-arm interferometer is connected with a first port of a second circulator 1-8, a second port of the first circulator 1-7 is connected with a first slave laser 1-2, a third port of the first circulator 1-7 is connected with a reflection end of a first beam splitter 1-9, a second port of the second circulator 1-8 is connected with a second slave laser 1-3, a third port of the second circulator 1-8 is connected with a transmission end of a first beam splitter 1-9, the first beam splitter 1-9 is connected with a filter 1-10, the filter 1-10 is connected with an attenuator 1-11, the attenuator 1-11 is connected with a transmission end of a wavelength division multiplexer 1-12, and a synchronous laser 1-4 is connected with a reflection end of the wavelength division multiplexer 1-12, the public end of the wavelength division multiplexer 1-12 of the receiving end is connected with the public end of the wavelength division multiplexer 1-14 of the transmitting end through a quantum channel 1-13;

the receiving end 92 includes: the device comprises a wavelength division multiplexer 1-14, a synchronous optical detector 1-15, a first beam splitter 1-16, a first single-photon detector 1-17, a circulator 1-18, a second beam splitter 1-19, a phase shifter 1-20, a first 90-degree Faraday reflector 1-21, a second 90-degree Faraday reflector 1-22, a second single-photon detector 1-23 and a third single-photon detector 1-24, wherein the second beam splitter 1-19, the phase shifter 1-20, the first 90-degree Faraday reflector 1-21, the second 90-degree Faraday reflector 1-22 and optical fibers connected with the second 90-degree Faraday reflector form a receiving end Michelson unequal arm interference module, the reflecting end of the wavelength division multiplexer 1-14 is connected with the synchronous optical detector 1-15, the transmitting end of the wavelength division multiplexer 1-14 is connected with the first beam splitter 1-16, the reflection end of the first beam splitter 1-16 is connected with the first single-photon detector 1-17, the transmission end of the first beam splitter is connected with the first port of the circulator 1-18, the third port of the circulator 1-18 is connected with the second single-photon detector 1-23, the second port of the circulator is connected with one end of the receiving end Michelson unequal-arm interferometer, and the other end of the receiving end Michelson unequal-arm interferometer is connected with the third single-photon detector 1-24.

In this embodiment, the implementation processes of the functions and actions of each instrument in the quantum key sending end and the quantum key receiving end are detailed in the corresponding implementation processes in the above embodiments, and are not described herein again.

The system error rate of the embodiment of the invention is not influenced by the channel polarization drift, the time bit coding is easy to realize and has high contrast, the time interval of the phase coding pulse of the sender is controlled by electronics, the matching of N senders and one receiver can be realized, and the large-scale networked deployment is facilitated. The quantum property of the beam splitter is used for passively realizing the phase bit coding of 0 and 180 degrees, the pulse laser injection technology is used for realizing the random phase of the signal pulse light prepared from the laser, the spectral line width and the time jitter of the signal pulse light are simultaneously narrowed to improve the interference contrast, and the time difference of pulse phase interference realized by a sender and a receiver is relaxed. The quantum key distribution system is simple in structure and easy to integrate.

Optionally, in another embodiment, the quantum key transmitting end and the quantum key receiving end may be integrated together through a circulator to form a transmitting-receiving integrated quantum key distribution terminal 10, a schematic diagram of a result of the quantum key distribution terminal is shown in fig. 10, and fig. 10 is a schematic diagram of a structure of a second application example of the quantum key distribution system provided in the embodiment of the present invention; the difference between the quantum key transmitting end and the quantum key receiving end in fig. 10 and fig. 9 is that the quantum channel in fig. 9 is replaced by a circulator, and the other parts are the same, and are not described one by one here.

Referring to fig. 11, a schematic structural diagram of a third application example of a quantum key distribution system according to an embodiment of the present invention is provided, where the embodiment is applied to a quantum key distribution system easy to be networked and encoded by a time phase BB84, as shown in fig. 11, and includes a quantum key transmitting end 21, a quantum key receiving end 22, and quantum channels 2 to 17, where the transmitting end 21 and the receiving end 22 are connected through the quantum channels 2 to 17. Wherein,

wherein, the quantum key transmitting end 21 includes: a master laser 2-1, a first slave laser 2-2, a second slave laser 2-3, a synchronous laser 2-4, a third circulator 2-5, a second beam splitter 2-6, a first 90-degree Faraday reflector 2-7, a second 90-degree Faraday reflector 2-8, a first 90-degree Faraday rotator 2-9, a second circulator 2-10, a second 90-degree Faraday rotator 2-11, a first circulator 2-12, a second beam splitter 2-13, a filter 2-14, an attenuator 2-15, a wavelength division multiplexer 2-16, wherein the second beam splitter 2-6, the first 90-degree Faraday reflector 2-7, the second 90-degree Faraday reflector 2-8 and optical fibers connected with the second beam splitter form a sending-end Michelson unequal arm interferometer, the master laser 2-1 is connected to a first port of the third circulator 2-5, a second port of the third circulator 2-5 is connected to one end of the sending-end michelson unequal arm interferometer, the other end of the sending-end michelson unequal arm interferometer is connected to the second 90-degree faraday rotator 2-11, a third port of the third circulator 2-5 is connected to the first 90-degree faraday rotator 2-9, the first 90-degree faraday rotator 2-9 is connected to a first port of the first circulator 2-10, a second port of the first circulator 2-10 is connected to the first slave laser 2-2, a third port of the first circulator 2-10 is connected to a reflection end of the second beam splitter 2-13, and a second port of the second circulator 2-12 is connected to the second slave laser 2-3, the third port of the second circulator 2-12 is connected with the transmission end of the first beam splitter 2-13, the first beam splitter 2-13 is connected with the filter 2-14, the filter 2-14 is connected with the attenuator 2-15, the attenuator 2-15 is connected with the transmission end of the wavelength division multiplexer 2-16, and the synchronous laser 2-4 is connected with the reflection end of the wavelength division multiplexer 2-16; the public end of the wavelength division multiplexer 2-18 of the quantum key receiving end is connected with the public end of the wavelength division multiplexer 2-16 of the sending end through a quantum channel 2-17;

the quantum key receiving end comprises: the wavelength division multiplexer 2-18, the synchronous optical detector 2-19, the first beam splitter 2-20, the first single-photon detector 2-21, the circulator 2-22, the second beam splitter 2-23, the phase shifter 2-24, the first 90-degree Faraday mirror 2-25, the second 90-degree Faraday mirror 2-26, the second single-photon detector 2-27 and the third single-photon detector 2-28, wherein the second beam splitter 2-23, the phase shifter 2-24, the first 90-degree Faraday mirror 2-25, the second 90-degree Faraday mirror 2-26 and optical fibers connected with the second beam splitter 2-23 form a receiving-end Michelson unequal-arm interferometer, the reflection end of the wavelength division multiplexer 2-18 is connected with the synchronous optical detector 2-19, the transmission end of the wavelength division multiplexer 2-18 is connected with the first beam splitter 2-20, the reflection end of the first beam splitter 2-20 is connected with the first single-photon detector 2-21, the transmission end of the first beam splitter 2-20 is connected with the first port of the circulator 2-22, the third port of the circulator 2-22 is connected with the second single-photon detector 2-27, the second port of the circulator 2-22 is connected with the receiving end Michelson unequal-arm interferometer, and the receiving end Michelson unequal-arm interferometer is connected with the third single-photon detector 2-28.

Optionally, in another embodiment, the quantum key transmitting terminal and the quantum key receiving terminal may be integrated together through a circulator to form a transmitting-receiving integrated quantum key distribution terminal.

In the embodiment of the invention, because the time interval of the phase coding pulse of the quantum key sending end is controlled by electrons, the matching of a plurality of quantum key sending ends and one quantum key receiving end can be realized, and the time difference of pulse phase interference realized by the quantum key sending ends and the quantum key receiving ends is reduced. The method utilizes the quantum property of a beam splitter to passively realize different phase bit coding, utilizes a pulse laser injection technology to realize the random phase of signal pulse light prepared from a laser, simultaneously narrows the spectral line width and time jitter to improve the interference contrast, and relaxes the time difference of pulse phase interference realized by a quantum key sending end and a quantum key receiving end. The quantum key distribution system is simple in structure and easy to integrate.

Referring to fig. 12, a flowchart of a quantum key sending method according to an embodiment of the present invention is provided, where the method includes:

step 101: triggering to generate a main laser pulse;

in this step, the phase of the main laser pulse is a randomized phase, which is modulated using a decoy method.

That is, the master laser emits a master laser pulse by internal modulation, the intrinsic phase of which is random, satisfying the phase randomization assumption of the decoy method.

The main laser pulse needs to be modulated by a decoy state method, preferably, the time bit is encoded into a signal state, the phase bit is encoded into two weak decoy states, and one vacuum state.

The modulation of the decoy state method can be that light pulses with different intensities are generated from signals with different amplitudes of driving voltage or current in the laser, or an external intensity modulator is used for modulating the intensity of the light pulses, or an external phase modulator is combined with a self-interference principle to generate light pulses with different intensities, or a plurality of slave lasers are combined with a fixed attenuator or beam splitters with different proportions to generate light pulses with different intensities.

Step 102: temporally dividing the main laser pulse into two identical main laser pulses;

in this step, one main laser pulse may be temporally divided into two identical main laser pulses by a mach-zehnder unequal arm interferometer, and a specific implementation process thereof is well known to the art and will not be described herein again.

Step 103: respectively injecting and locking the two same main laser pulses, and controlling the two same main laser pulses through voltages with different intensities to generate slave laser pulses with different intensities;

two different slave laser pulses are respectively used for injection locking the slave laser, and the two same master laser pulses are controlled by voltages with different intensities to generate the slave laser pulses, namely, the slave laser generates a time bit code of one pulse or a phase bit code of two pulses under the action of driving voltages or currents generated under the control of different random numbers, and the time interval of the two pulses of the phase bit code is precisely controlled by electronics.

Step 104: modulating and coding the slave laser pulses with different intensities to obtain quantum signal light;

the process of modulation encoding the slave laser pulses with different intensities in this step is well known to those skilled in the art and will not be described herein.

Step 105: filtering and attenuating the quantum signal light to obtain quantum signal light with a single photon level;

step 106: and transmitting the quantum signal light of the single photon level and the generated classical synchronous signal to a receiving end after wavelength division multiplexing.

Referring to fig. 13, a flowchart of a quantum key transceiving method according to an embodiment of the present invention is provided, where the quantum key transceiving method includes:

step 201: triggering and generating a main laser pulse by a sending end;

step 202: the main laser pulse of the sending end is divided into two same main laser pulses in time;

step 203: the sending end respectively controls the voltage of the two same main laser pulses with different intensities to generate slave laser pulses with different intensities;

step 204: the transmitting end modulates and codes the slave laser pulses with different intensities to obtain quantum signal light;

step 205: the sending end filters and attenuates the quantum signal light to obtain the quantum signal light with single photon level;

step 206: the transmitting end transmits the quantum signal light of the single photon level and the generated classical synchronous signal to a receiving end through a quantum channel after wavelength division multiplexing;

step 207: the receiving end demultiplexes the quantum signal light of the single photon level received through the quantum channel and the generated classical synchronous signal to obtain a classical synchronous signal and quantum signal light;

step 208: the receiving end carries out passive basis vector selection, Z basis vector time bit measurement and X basis vector phase bit measurement on the quantum signal light, and determines the error rate of X basis vectors;

step 209: and the receiving end adjusts the phase reference coefficient of the receiving end and the transmitting end according to the error rate of the X basis vector.

In this embodiment, the control method for respectively performing voltage control on the two same main laser pulses with different intensities includes: generating light pulses with different intensities by internal driving voltage or current signals with different amplitudes; or an external intensity modulator is used for modulating the intensity of the light pulse; or the external phase modulator is combined with the self-interference principle to generate light pulses with different intensities; or multiple pulses of light of different intensities generated from a laser in combination with a fixed attenuator or a different proportional beam splitter.

It should be noted that, for simplicity of description, the method embodiments are described as a series of acts or combination of acts, but those skilled in the art will recognize that the present invention is not limited by the illustrated order of acts, as some steps may occur in other orders or concurrently in accordance with the embodiments of the present invention. Further, those skilled in the art will appreciate that the embodiments described in the specification are presently preferred and that no particular act is required to implement the invention.

The embodiments in the present specification are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.

As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, apparatus, or computer program product. Accordingly, embodiments of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, embodiments of the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

Embodiments of the present invention are described with reference to flowchart illustrations and/or block diagrams of methods, terminal devices (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing terminal to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing terminal, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing terminal to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing terminal to cause a series of operational steps to be performed on the computer or other programmable terminal to produce a computer implemented process such that the instructions which execute on the computer or other programmable terminal provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

While preferred embodiments of the present invention have been described, additional variations and modifications of these embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the embodiments of the invention.

Finally, it should also be noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or terminal that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or terminal. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or terminal that comprises the element.

The quantum key transmitting end, the receiving end, the transceiving system and the method thereof provided by the invention are described in detail, a specific example is applied in the text to explain the principle and the implementation mode of the invention, and the description of the embodiment is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.

Claims

1. A quantum key transmitting end, comprising: a master laser, a first slave laser, a second slave laser, a synchronous laser, an unequal arm interferometer, a first circulator, a second circulator, a first beam splitter, a filter, an attenuator and a wavelength division multiplexer, wherein the master laser is connected with the unequal arm interferometer, one end of the unequal arm interferometer is connected with a first port of the first circulator, the other end of the unequal arm interferometer is connected with a first port of the second circulator, a second port of the first circulator is connected with the first slave laser, a third port of the first circulator is connected with a reflection end of the first beam splitter, a second port of the second circulator is connected with the second slave laser, a third port of the second circulator is connected with a transmission end of the first beam splitter, the first beam splitter is connected with the filter, and the filter is connected with the attenuator, the attenuator is connected with the transmission end of the wavelength division multiplexer, and the synchronous laser is connected with the reflection end of the wavelength division multiplexer; the unequal arm interferometer divides a main laser pulse emitted by the main laser into two same main laser pulses in time, and the two same main laser pulses are respectively injection-locked to the first slave laser and the second slave laser to generate slave laser pulses; when the master laser pulse is injected, voltages with different intensities are triggered to the first slave laser and the second slave laser, so that the first slave laser and the second slave laser emit slave laser pulses with different intensities, the slave laser pulses are input to a first beam splitter, the first beam splitter adjusts and codes the received slave laser pulses with different intensities to obtain quantum signal light, and the quantum signal light passes through a filter and an attenuator and is emitted after passing through a wavelength division multiplexer together with a classical synchronous light signal generated by a synchronous laser.

2. A transmitter according to claim 1, wherein the unequal-arm interferometer comprises: the transmission end of the first beam splitter is connected with the transmission end of the second beam splitter, and the reflection end of the first beam splitter is connected with the reflection end of the second beam splitter; the first beam splitter is further connected with the main laser, and the second beam splitter is further connected with the first circulator and the second circulator respectively.

3. The transmitter according to claim 1, wherein the transmitter further comprises: first 90 degrees Faraday rotator, second 90 degrees Faraday rotator and third circulator, wherein, the first port of third circulator is connected with main laser, the second port of third circulator is connected the one end of inequality arm interferometer, the other end of inequality arm interferometer is connected second 90 degrees Faraday rotator, the third port of third circulator is connected first 90 degrees Faraday rotator, first 90 degrees Faraday rotator is connected the first port of first circulator.

4. A transmitter according to claim 3, wherein the unequal-arm interferometer comprises: the beam splitter comprises a fourth beam splitter, a first 90-degree Faraday reflector and a second 90-degree Faraday reflector; and the fourth beam splitter is respectively connected with the second port of the third circulator, the first 90-degree Faraday reflector, the second 90-degree Faraday reflector and the second 90-degree Faraday rotator.

5. The transmitting end according to any one of claims 1 to 4, wherein the first ports of the first circulator, the second circulator and the third circulator are inlets of optical signals, and the second ports are outlets of optical signals; or the second port is an inlet of the optical signal, and the third port is an outlet of the optical signal.

6. A transmitting end according to any one of claims 1 to 4, characterized in that the phase of the primary laser pulse transmitted by the primary laser is a randomized phase, and the randomized phase is modulated by adopting a decoy method.

7. The transmitting end according to claim 6, wherein the randomized phase is modulated by using a spoof method comprising:

8. The transmitting end according to any one of claims 1 to 4, wherein the wavelength division multiplexer has a common end for transmitting both quantum signal light and classical synchronous light, and wherein the wavelength division multiplexer has a transmitting end for transmitting quantum signal light and a reflecting end for transmitting classical synchronous light.

9. A receiving end of a quantum key, comprising:

10. The receiving end of claim 9, wherein the unequal-arm interferometer comprises: the phase shifter comprises a second beam splitter, a phase shifter, a first 90-degree Faraday reflector and a second 90-degree Faraday reflector, wherein the beam splitter is respectively connected with a second port of the circulator, the second 90-degree Faraday reflector, the phase shifter and a third single photon detector, and the phase shifter is also connected with the first 90-degree Faraday reflector.

11. A system for transmitting and receiving a quantum key, comprising: a sending end of the quantum key, a receiving end of the quantum key, and a quantum channel or circulator, wherein the sending end of the sub-key and the receiving end of the sub-key are connected through the quantum channel or circulator,

the transmitting end of the quantum key is as claimed in any one of claims 1 to 8;

the receiving end of the quantum key is as claimed in claim 9 or 10.

12. A quantum key sending method according to claim 1, comprising:

triggering to generate a main laser pulse;

temporally dividing the main laser pulse into two identical main laser pulses;

13. The transmission method according to claim 12, wherein the phase of the main laser pulse is a randomized phase, and the randomized phase is modulated by a decoy method.

14. The transmission method of claim 13, wherein the spoof state method modulation comprises:

15. A method for transceiving quantum keys based on claim 11, comprising:

triggering and generating a main laser pulse by a sending end;

16. The transmission/reception method according to claim 15, wherein the controlling of the voltages of the two identical main laser pulses with different intensities includes: