Quantum light source system and quantum light output method

Abstract

The invention relates to the field of quantum communication, and discloses a quantum light source system and a quantum light output method. The quantum light source system comprises an electric signal generator and an output part; the electric signal generator is used for outputting three kinds of electric pulses with different intensities; the output part is used for outputting four different polarization state optical signals; the electric signal generator is electrically connected with the output part, and the electric signal generator outputs three electric pulses with different intensities to the output part to excite the output part to output optical signals with three intensity states and four polarization states, so that the requirements of a quantum key distribution system are met; the intensity of the output part is directly modulated through the electric signal generator, an additional modulator assembly is not needed, the risk of information leakage of the output part is reduced, and the safety of the quantum key distribution system is ensured.

Description

Technical Field

[0001] The present invention relates to the field of quantum communication, and in particular to a quantum light source system and a quantum light output method. Background Art

[0002] Quantum communication, especially quantum key distribution (QKD), has attracted much attention as an emerging encryption technology due to its inherent security based on the principles of quantum mechanics. Mainstream high-speed QKD systems generally adopt a design based on a combination of continuous lasers, intensity modulators, and phase modulators to achieve high-speed modulation and improve the coding rate of the entire system.

[0003] However, this scheme also comes with significant disadvantages. Due to the use of active modulators such as intensity modulators and phase modulators, they will inevitably generate additional physical information during operation. Attackers may further infer key information by capturing and analyzing the physical information leaked by the active modulators, thus seriously threatening the security of the QKD system.

[0004] Therefore, how to effectively prevent the leakage of quantum light source information caused by active modulators and ensure the overall security of the QKD system has become a technical problem that needs to be solved urgently. Summary of the invention

[0005] The present invention aims to improve at least one technical problem in the background technology.

[0006] The first aspect of the present invention provides a quantum light source system, comprising: an electrical signal generator and an output unit; the electrical signal generator is used to output electrical pulses with three intensity states; the output unit is used to output four different polarization state optical signals; The output unit includes four slave lasers, a first fiber polarization beam splitter, a second fiber polarization beam splitter, a half-wave plate and a first beam splitter; The input ends of the four slave lasers are all electrically connected to the electrical signal generator; The output ends of any two of the slave lasers are respectively connected to the two input ends of the first optical fiber polarization beam splitter, and the output end of the first optical fiber polarization beam splitter is connected to the input end of the first optical beam splitter; The output ends of the other two slave lasers are respectively connected to the two input ends of the second optical fiber polarization beam splitter, the output end of the second optical fiber polarization beam splitter is connected to the input end of the first optical beam splitter, and the half-wave plate is further provided between the output end of the second optical fiber polarization beam splitter and the input end of the first optical beam splitter; The electrical signal generator outputs electrical pulses with three intensity states to the four slave lasers to stimulate the four slave lasers to output four optical signals with three intensity states. The four optical signals are converted into four polarized light signals after passing through the first optical fiber polarization beam splitter, the second optical fiber polarization beam splitter and the half-wave plate, and are combined by the first optical beam splitter, so that the optical signal output by the output part has three intensity states and four polarization states.

[0007] The beneficial effects of the embodiments of the first aspect of the present invention are as follows: the quantum light source of the present invention includes an electrical signal generator and an output unit, the electrical signal generator can output three electrical pulses with different intensities, and the output unit can output four different polarization state light signals; the output unit is stimulated by the electrical signal generator so that the light signal output by the output unit has three intensity states and four polarization states, which can meet the requirements of the quantum key distribution system; because the intensity of the output unit is modulated directly by the electrical signal generator, no additional modulator component is required, which reduces the risk of information leakage in the output unit and ensures the security of the quantum key distribution system.

[0008] As some sub-solutions of the above technical solution, the electrical signal generator includes four first output terminals; the four first output terminals are electrically connected to the four slave lasers respectively; the four first output terminals output electrical pulses with three intensity states to the slave lasers respectively.

[0009] As some sub-solutions of the above technical solution, the output unit also includes an attenuator; the attenuator is connected to the output end of the first beam splitter, and the attenuator is used to attenuate the optical signal output by the first beam splitter into a quantum pulse of the single photon order.

[0010] As some sub-schemes of the above technical scheme, the output part also includes four sub-beam splitters; the four slave lasers are respectively connected to the first optical fiber polarization beam splitter or the second optical fiber polarization beam splitter through the four sub-beam splitters; the sub-beam splitter is used to split the optical signal output by the slave laser into two parts of the optical signal, one part of the optical signal enters the first optical fiber polarization beam splitter or the second optical fiber polarization beam splitter, and the other part of the optical signal is output as detection light to the outside of the system.

[0011] As some sub-solutions of the above technical solution, the slave laser is a DFB type laser.

[0012] As some sub-schemes of the above technical scheme, the quantum light source system also includes a master laser, and the electrical signal generator also includes a second output end; the second output end is used to output an electrical pulse having an intensity state; the master laser is electrically connected to the second output end and receives the electrical pulse having an intensity state output by the second output end; the master laser is connected to the slave laser and outputs light pulses to the slave laser; the light pulse output by the master laser matches the waveform of the electrical pulse output by the second output end.

[0013] As some sub-schemes of the above technical scheme, the quantum light source system also includes four optical circulators; the optical circulators are connected between the master laser and the slave laser; all the optical circulators include a first port, a second port and a third port; the optical pulse output by the master laser is input into the optical circulator from the first port and output to the slave laser through the second port, and the optical signal output by the slave laser is input into the optical circulator through the second port and output from the optical circulator through the third port.

[0014] As some sub-schemes of the above technical scheme, the quantum light source system also includes a second beam splitter, a third beam splitter and a fourth beam splitter; the output end of the main laser is connected to the input end of the second beam splitter, the two output ends of the second beam splitter are respectively connected to the input ends of the third beam splitter and the fourth beam splitter, and the two output ends of the third beam splitter and the two output ends of the fourth beam splitter are respectively connected to the first ports of the four optical circulators.

[0015] A second aspect of the present invention provides a quantum light output method, which is used to control the operation of the quantum light source system as described in the above embodiment. The quantum light output method comprises the steps of: An electric signal generator is used to input electric pulses with three different intensities to four slave lasers; An electric signal generator is used to input an electric pulse with a certain intensity state into a main laser, so as to stimulate the main laser to output an optical pulse matching the electric pulse waveform output by the electric signal generator, and a beam splitter is used to divide the optical pulse into four paths; The four optical pulses are input into four slave lasers through an optical circulator, so that the four slave lasers respectively output four optical signals under the stimulation of the electrical pulses and the optical pulses; Inputting any two of the four optical signals into the first optical fiber polarization beam splitter to generate two polarized lights; Inputting the other two of the four optical signals into the second optical fiber polarization beam splitter and the half-wave plate in sequence to generate the other two polarized lights; The four polarized lights are sequentially input into the first beam splitter and attenuator for beam combining and attenuation processing to obtain quantum light of single photon order.

[0016] The beneficial effects of the second aspect of the embodiment of the present invention are as follows: an electric signal generator is used to output an electric pulse to excite the slave laser, and the slave laser is internally modulated so that the optical signal output by the slave laser obtains three intensity states; then passive devices such as an optical fiber polarization beam splitter and an optical beam splitter are used to obtain four polarization states of the optical signal output by the slave laser; finally, the optical signal output by the slave laser has three intensity states and four polarization states, which can meet the requirements of the quantum key distribution system; at the same time, in order to ensure the stability of the optical pulse during high-speed modulation, the main laser is stimulated by an electric signal generator, so that the main laser outputs an optical pulse that is injected into the spectrum of the locked slave laser to achieve consistency in spectrum, intensity and space; different from the active modulation scheme, the present invention realizes full passive modulation through internal modulation and passive devices, thereby ensuring the security of the quantum key distribution system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which: Figure 1 A schematic diagram of the structure of a quantum light source system provided by an embodiment of the present invention; Figure 2 Schematic diagram of generating light pulses for electrical pulse stimulation of lasers; Figure 3 This is a schematic diagram of the working principle of the optical circulator; Figure 4 A flow chart of a quantum light output method provided in an embodiment of the present invention.

[0018] In the attached figure: 1-electrical signal generator; 11-first output terminal; 12-second output terminal; 2-slave laser; 21-first optical fiber polarization beam splitter; 22-second optical fiber polarization beam splitter; 23-half-wave plate; 24-first beam splitter; 25-attenuator; 26-sub-beam splitter; 3-main laser; 31-optical circulator; 311-first port; 312-second port; 313-third port; 32-second beam splitter; 33-third beam splitter; 34-fourth beam splitter. DETAILED DESCRIPTION

[0019] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0020] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0021] In the description of the present invention, the meaning of "several" is an indefinite quantity, the meaning of "multiple" is more than two, "greater than", "less than", "exceed", etc. are understood as not including the number itself, and "above", "below", "within", etc. are understood as including the number itself. If there is a description of the first and the second, it is only for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features. The "and / or" that appears in the full text represents three parallel solutions. For example, A and / or B represents the solution satisfied by A, the solution satisfied by B, or the solution satisfied by both A and B.

[0022] In the description of the present invention, if there is a short sentence containing multiple parallel features, the attributive defines the closest feature, for example: B, C, and E connected to D are arranged on A, which means that B is arranged on A and E is connected to D, and does not constitute a limitation on C; but attributives that indicate the relationship between features, such as "interval arrangement" or "circular arrangement", do not belong to this category. If the word "all" is preceded by an attributive, it means that all features in the short sentence are limited, such as B, C, and D are all arranged on A, which means that B, C, and D are all arranged on A. For a sentence with an omitted subject, the omitted subject is the subject of the previous sentence, that is, B is arranged on A, including C, which means that B is arranged on A and A includes C.

[0023] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific content of the technical solution.

[0024] Combine the following Figures 1 to 4 Embodiments of the present invention are described.

[0025] A quantum light source system in an embodiment of the first aspect of the present invention comprises: An electrical signal generator 1 and an output unit; the electrical signal generator 1 is used to output electrical pulses with three intensity states; the output unit is used to output optical signals with four different polarization states; The output unit includes four slave lasers 2, a first fiber polarization beam splitter 21, a second fiber polarization beam splitter 22, a half-wave plate 23 and a first beam splitter 24; The input ends of the four slave lasers 2 are all electrically connected to the electrical signal generator 1; The output ends of any two slave lasers 2 are respectively connected to the two input ends of the first optical fiber polarization beam splitter 21, and the output end of the first optical fiber polarization beam splitter 21 is connected to the input end of the first optical beam splitter 24; The other two output ends of the slave laser 2 are respectively connected to the two input ends of the second optical fiber polarization beam splitter 22, and the output end of the second optical fiber polarization beam splitter 22 is connected to the input end of the first beam splitter 24. A half-wave plate 23 is also provided between the output end of the second optical fiber polarization beam splitter 22 and the input end of the first beam splitter 24. The electrical signal generator 1 outputs electrical pulses of three intensity states to the four slave lasers 2 to stimulate the four slave lasers 2 to output four optical signals with three intensity states. The four optical signals are converted into four polarized light signals after passing through the first optical fiber polarization beam splitter 21, the second optical fiber polarization beam splitter 22 and the half-wave plate 23, and are combined by the first optical beam splitter 24, so that the optical signal output by the output part has three intensity states and four polarization states.

[0026] The quantum light source system of the first embodiment of the present invention is applied to the quantum key distribution (QKD) system. The current mainstream QKD system is based on the BB84 protocol design of the decoy state, and uses weak coherent light pulses to replace the single photon source. However, the existing QKD system has the risk of information leakage, and its quantum light source is likely to be attacked. Specifically, when the quantum light source is modulated by active modulators such as intensity modulators and phase modulators, it will cause source information leakage; that is, actively modulating the quantum light source will cause information leakage risk. In order to solve this problem, the quantum light source of the first embodiment of the present invention adopts a passive modulation method, and uses the electrical signal generator 1 to output an electrical pulse to excite the output part, thereby realizing internal modulation, avoiding source information leakage caused by active modulation, and ensuring the security of the QKD system.

[0027] Specifically, the electric signal generator 1 is electrically connected to the output part, and the electric signal generator 1 is first used to output three electric pulses of different intensities to stimulate the four slave lasers 2 to output four optical signals with three intensity states. The four optical signals enter the first optical fiber polarization beam splitter 21 and the second optical fiber polarization beam splitter 22 respectively. The optical fiber polarization beam splitter can separate or merge light with the same polarization direction. In this system, the two slave lasers 2 are respectively input into the two orthogonal ports of the optical fiber polarization beam splitter, so two polarization states can be separated. At this time, the polarization states of the light output by the first optical fiber polarization beam splitter 21 and the second optical fiber polarization beam splitter 22 are the same; in order to achieve four polarization states, it is necessary to add a half-wave plate 23 behind the second optical fiber polarization beam splitter 22, and use the half-wave plate 23 to select the polarization direction of the light, so that the second optical fiber polarization beam splitter 22 can output two polarized lights different from the first optical fiber polarization beam splitter 21, and the system completes the output of four polarized lights. Finally, these four polarized lights enter the first optical beam splitter 24 to complete the beam combination. By modulating polarized light with passive components such as the first optical fiber polarization beam splitter 21, the second optical fiber polarization beam splitter 22, the first optical beam splitter 24 and the half-wave plate 23, internal modulation is achieved without causing information leakage, thereby ensuring the security of the system.

[0028] The combination of the electrical signal generator 1 and the output part allows the output optical signal to have three intensity states and four polarization states, which meets the requirements for the implementation of the BB84 protocol QKD system in a decoyed state. The quantum light output through this internal modulation method is safer and avoids the risk of information leakage caused by active modulation.

[0029] Specifically, the electrical signal generator 1 includes four first output terminals 11; the electrical signal generator 1 includes four first output terminals 11; the four first output terminals 11 are electrically connected to four slave lasers 2 respectively; the four first output terminals 11 output electrical pulses with three intensity states to the slave lasers 2 respectively.

[0030] The four first output ends 11 independently output three electric pulses of different intensities, which are transmitted to the slave laser 2 in the output part through electrical connection, and serve as excitation signals to drive the slave laser 2 to generate corresponding optical signals. The four first output ends 11 correspond to the four polarized lights output by the output part respectively; Figure 2 The first output terminal 11 outputs three electrical pulses of different intensities to the output part to stimulate the slave laser 2 in the output part to generate three optical pulses of different intensities.

[0031] The electric signal generator 1 is a control circuit that integrates multiple control components, including but not limited to a main control chip (such as TMS320F28377D-EP), a driver chip (such as TLP250), a power device (such as IGBT or MOSFET), a signal detection chip (such as Hall sensor) and a protection chip (such as TPS25910); the main control chip generates three PWM signals with different duty cycles or frequencies according to a preset algorithm or program, and different PWM signals correspond to electric pulses of different intensities. The main control chip outputs a PWM control signal to the driver chip, and the driver chip is used to amplify the PWM control signal output by the main control chip to drive the power device. After receiving the signal, the power device outputs three electric pulse signals of different intensities; the signal detection chip is used to monitor the current, voltage and other parameters of the power device in real time; the protection chip is used to monitor the working status of the power device and the circuit as a whole; these components work together to ensure that the electric signal generator 1 can accurately output three electric pulses of different intensities.

[0032] Specifically, the output unit further includes an attenuator 25 ; the attenuator 25 is connected to the output end of the first beam splitter 24 , and is used to attenuate the optical signal output by the first beam splitter 24 into a quantum pulse of the order of single photons.

[0033] The addition of the attenuator 25 causes the optical signal output by the first beam splitter 24 to be attenuated into a quantum pulse of the order of single photons, which is a key requirement in the quantum key distribution system, because the single photon pulse can ensure the quantum characteristics of information transmission, thereby improving the security of the system. Finally, the quantum pulse processed by the attenuator 25 can be used for information transmission in the process of quantum key distribution.

[0034] Specifically, the output part also includes four sub-beam splitters 26; the four slave lasers 2 are respectively connected to the first optical fiber polarization beam splitter 21 or the second optical fiber polarization beam splitter 22 through the four sub-beam splitters 26; the sub-beam splitter 26 is used to split the optical signal output from the laser 2 into two parts of the optical signal, one part of the optical signal enters the first optical fiber polarization beam splitter 21 or the second optical fiber polarization beam splitter 22, and the other part of the optical signal is output as a detection light to the outside of the system.

[0035] The four slave lasers 2 output four optical signals under the stimulation of the electrical pulse of the electrical signal generator 1. After each optical signal enters the corresponding sub-beam splitter 26, it is split into two parts. One part of the optical signal continues to enter the first optical fiber polarization beam splitter 21 or the second optical fiber polarization beam splitter 22 for polarization modulation; the detection light can be used to monitor the output status of the slave laser 2, the stability of the optical fiber connection, and the optical loss inside the system and other key parameters. By monitoring these parameters in real time, the system can promptly detect and deal with potential problems, thereby improving the stability and reliability of the system.

[0036] Specifically, the slave laser 2 is a DFB type laser.

[0037] DFB laser can output stable and pure optical signals. The output optical signals have narrow spectral linewidth and high sideband suppression ratio, which reduces mode competition and noise interference and improves the communication efficiency and stability of the system.

[0038] Reference Figure 2 A semiconductor laser is a device that uses electron-hole recombination in semiconductor materials to generate light. When an electric pulse is applied to the electrode of a semiconductor laser, it will produce an instantaneous current change in the active region of the laser. This current change causes the number of electrons and holes in the active region to change, thereby changing the rate of electron-hole recombination. The recombined electrons and holes will release energy, part of which is emitted in the form of photons. The amplitude of the electric pulse determines the current applied to the laser, thereby affecting the rate of electron-hole recombination and the number of photons emitted. Therefore, electric pulses of different amplitudes will cause the laser to produce light pulses of different intensities. Refer to Figure 2 By adjusting the amplitude of the electric pulse, three light pulses with different intensities, namely signal state (S), decoy state (D) and vacuum state (V), can be generated respectively.

[0039] Specifically, the quantum light source system also includes a master laser 3, and the electrical signal generator 1 also includes a second output terminal 12; the second output terminal 12 is used to output an electrical pulse having an intensity state; the master laser 3 is electrically connected to the second output terminal 12 and receives the electrical pulse having an intensity state output by the second output terminal 12; the master laser 3 is connected to the slave laser 2 and outputs an optical pulse to the slave laser 2; the optical pulse output by the master laser 3 matches the waveform of the electrical pulse output by the second output terminal 12.

[0040] In order to improve the time stability and intensity stability of the optical pulse, the present embodiment adopts an injection locking method. Specifically, the master laser 3 outputs a pulse with a waveform similar to the electrical pulse, which is injected into the slave laser 2. The slave laser 2 generates an optical pulse under the excitation of the electrical pulse and the master laser, and the spectrum of the slave laser 2 is locked to achieve the consistency of the optical signal in spectrum, intensity and space, effectively reduce the time jitter and intensity jitter of the optical pulse of the slave laser 2, and improve the stability and consistency of the optical pulse.

[0041] Specifically, the quantum light source system also includes four optical circulators 31; the optical circulators 31 are connected between the master laser 3 and the slave laser 2; all optical circulators 31 include a first port 311, a second port 312 and a third port 313; the optical pulse output by the master laser 3 is input into the optical circulator 31 from the first port 311, and is output to the slave laser 2 through the second port 312, and the optical signal output by the slave laser 2 is input into the optical circulator 31 through the second port 312, and is output from the optical circulator 31 through the third port 313.

[0042] The use of the optical circulator 31 ensures unidirectional transmission of the optical signal, prevents the optical pulse of the main laser 3 from being directly reflected back to the main laser 3, thereby avoiding possible damage to the light source or performance degradation, avoiding reflection and interference of the optical signal, and improving the stability of the quantum light source system.

[0043] Specifically, the quantum light source system also includes a second beam splitter 32, a third beam splitter 33 and a fourth beam splitter 34; the output end of the main laser 3 is connected to the input end of the second beam splitter 32, the two output ends of the second beam splitter 32 are respectively connected to the input ends of the third beam splitter 33 and the fourth beam splitter 34, and the two output ends of the third beam splitter 33 and the two output ends of the fourth beam splitter 34 are respectively connected to the first ports 311 of the four optical circulators 31.

[0044] The second beam splitter 32, the third beam splitter 33 and the fourth beam splitter 34 are mainly used to transmit the optical signal output by the master laser 3 to the four slave lasers 2 respectively; the second beam splitter 32, as the primary link of optical pulse distribution, receives the optical pulse output by the master laser 3 and divides it into two equal optical pulses, and the third beam splitter 33 and the fourth beam splitter 34 respectively receive the two optical pulses output by the second beam splitter 32, and divide them into two equal optical pulses respectively, so that the optical pulse output by the master laser 3 is divided into four paths, and the four paths of optical pulses enter the four slave lasers 2 respectively. Through this light splitting method, the utilization efficiency of the optical pulses is improved, and the consistency of the four lasers in the spectral dimension is also guaranteed.

[0045] Reference Figure 4 The second aspect of the present invention provides a quantum light output method, which is used to control the operation of the quantum light source system described in the above embodiment. The quantum light output method includes the steps of: 101. Using an electrical signal generator 1, inputting electrical pulses with three different intensities into four slave lasers 2; 102. Using the electric signal generator 1 to input an electric pulse with one intensity state into the main laser 3, the main laser 3 is stimulated to output an optical pulse matching the electric pulse waveform output by the electric signal generator 1, and the optical pulse is divided into four paths by using a beam splitter; 103. Input four optical pulses into four slave lasers 2 through the optical circulator 31, so that the four slave lasers 2 respectively output four optical signals under the stimulation of the electrical pulses and the optical pulses; 104. Input any two of the four optical signals into the first optical fiber polarization beam splitter 21 to generate two polarized lights; 105. Input the other two of the four optical signals into the second optical fiber polarization beam splitter 22 and the half-wave plate 23 in sequence to generate another two polarized lights; 106. Input the four polarized lights into the first beam splitter 24 and the attenuator 25 in sequence for beam combining and attenuation processing to obtain quantum light of single photon order.

[0046] The quantum light output method provided in the embodiment of the second aspect of the present invention is an innovative improvement on the quantum light output method of the traditional QKD system. It abandons the traditional practice of relying on continuous lasers in combination with intensity modulators and phase modulators to achieve quantum light modulation, and instead adopts internal modulation and passive devices to achieve quantum light modulation, avoiding the risk of information leakage introduced by intensity modulators and phase modulators, and significantly improving the security of the QKD system.

[0047] Specifically, three electric pulses of different intensities are accurately input to four slave lasers 2 through the electric signal generator 1. At the same time, the electric signal generator 1 excites the master laser 3 to output optical pulses, and the optical beam splitter is used to cleverly divide these optical pulses into four paths. Subsequently, the optical circulator 31 sends these four optical pulses to the four slave lasers 2 without loss. Under the dual excitation of the electric pulse and the optical pulse, the slave laser 2 stably outputs four optical signals, and uses passive devices such as the optical fiber polarization beam splitter and the half-wave plate 23 to polarize and modulate the four optical signals to generate four optical signals with different polarization states. Finally, these polarized lights are combined into one beam through the first beam splitter 24, and then finely adjusted to the single photon level by the attenuator 25, so as to achieve the stable output of quantum light.

[0048] The preferred embodiments of the present invention are described in detail above, but the present disclosure is not limited to the embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of the present disclosure.

Claims

1. A quantum light source system, characterized in that: include: An electrical signal generator (1) and an output unit; the electrical signal generator (1) is used to output electrical pulses having three intensity states; the output unit is used to output optical signals of four different polarization states; The output unit comprises four slave lasers (2), a first optical fiber polarization beam splitter (21), a second optical fiber polarization beam splitter (22), a half-wave plate (23) and a first optical beam splitter (24); The input ends of the four slave lasers (2) are all electrically connected to the electrical signal generator (1); The output ends of any two slave lasers (2) are respectively connected to the two input ends of the first optical fiber polarization beam splitter (21), and the output end of the first optical fiber polarization beam splitter (21) is connected to the input end of the first optical beam splitter (24); The other two output ends of the slave lasers (2) are respectively connected to the two input ends of the second optical fiber polarization beam splitter (22), the output end of the second optical fiber polarization beam splitter (22) is connected to the input end of the first optical beam splitter (24), and the half-wave plate (23) is further provided between the output end of the second optical fiber polarization beam splitter (22) and the input end of the first optical beam splitter (24); The electrical signal generator (1) outputs electrical pulses of three intensity states to the four slave lasers (2) to stimulate the four slave lasers (2) to output four optical signals of three intensity states. The four optical signals are converted into four polarized optical signals after passing through the first optical fiber polarization beam splitter (21), the second optical fiber polarization beam splitter (22) and the half-wave plate (23). The four optical signals are combined by the first optical beam splitter (24) so ​​that the optical signals output by the output unit have three intensity states and four polarization states.

2. The quantum light source system according to claim 1, characterized in that: The electrical signal generator (1) comprises four first output ends (11); the four first output ends (11) are electrically connected to the four slave lasers (2) respectively; the four first output ends (11) output electrical pulses having three intensity states to the slave lasers (2) respectively.

3. The quantum light source system according to claim 1, characterized in that: The output unit further comprises an attenuator (25); the attenuator (25) is connected to the output end of the first light beam splitter (24), and the attenuator (25) is used to attenuate the light signal output by the first light beam splitter (24) into a quantum pulse of the order of single photons.

4. The quantum light source system according to claim 1, characterized in that: The output unit further comprises four sub-beam splitters (26); the four slave lasers (2) are respectively connected to the first optical fiber polarization beam splitter (21) or the second optical fiber polarization beam splitter (22) via the four sub-beam splitters (26); the sub-beam splitters (26) are used to split the optical signal output by the slave laser (2) into two parts of optical signals, one part of the optical signal enters the first optical fiber polarization beam splitter (21) or the second optical fiber polarization beam splitter (22), and the other part of the optical signal is output as detection light to the outside of the system.

5. The quantum light source system according to claim 1, characterized in that: The slave laser (2) is a DFB type laser.

6. The quantum light source system according to claim 1, characterized in that: The quantum light source system further comprises a master laser (3), and the electrical signal generator (1) further comprises a second output end (12); the second output end (12) is used to output an electrical pulse having a state of intensity; the master laser (3) is electrically connected to the second output end (12) and receives the electrical pulse having a state of intensity output by the second output end (12); the master laser (3) is connected to the slave laser (2) and outputs an optical pulse to the slave laser (2); the optical pulse output by the master laser (3) matches the waveform of the electrical pulse output by the second output end (12).

7. The quantum light source system according to claim 6, characterized in that: The quantum light source system further comprises four optical circulators (31); the optical circulators (31) are connected between the master laser (3) and the slave laser (2); all the optical circulators (31) comprise a first port (311), a second port (312) and a third port (313); the optical pulse output by the master laser (3) is input into the optical circulator (31) through the first port (311) and is output to the slave laser (2) through the second port (312); the optical signal output by the slave laser (2) is input into the optical circulator (31) through the second port (312) and is output from the optical circulator (31) through the third port (313).

8. The quantum light source system according to claim 7, characterized in that: The quantum light source system further comprises a second beam splitter (32), a third beam splitter (33) and a fourth beam splitter (34); the output end of the master laser (3) is connected to the input end of the second beam splitter (32), the two output ends of the second beam splitter (32) are respectively connected to the input ends of the third beam splitter (33) and the fourth beam splitter (34), and the two output ends of the third beam splitter (33) and the two output ends of the fourth beam splitter (34) are respectively connected to the first ports (311) of the four optical circulators (31).

9. A quantum light output method, characterized in that: The quantum light output method is used to control the operation of the quantum light source system according to any one of claims 1 to 8, and the quantum light output method comprises the steps of: An electric signal generator (1) is used to input electric pulses having three different intensities to four slave lasers (2); An electric signal generator (1) is used to input an electric pulse having a certain intensity state into a main laser (3), thereby stimulating the main laser (3) to output an optical pulse having a waveform matching the electric pulse output by the electric signal generator (1), and a beam splitter is used to split the optical pulse into four paths; The four optical pulses are input into the four slave lasers (2) through an optical circulator (31), so that the four slave lasers (2) respectively output four optical signals under the stimulation of the electrical pulses and the optical pulses; Inputting any two of the four optical signals into a first optical fiber polarization beam splitter (21) to generate two polarized lights; Inputting the other two of the four optical signals into the second optical fiber polarization beam splitter (22) and the half-wave plate (23) in sequence to generate the other two polarized lights; The four polarized lights are sequentially input into a first beam splitter (24) and an attenuator (25) for beam combining and attenuation processing, so as to obtain single-photon quantum light.

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