Time-phase high-speed quantum key coding system based on injection locking

Abstract

The utility model discloses a time-phase high-speed quantum key coding system based on injection locking. The time-phase high-speed quantum key coding system comprises a first laser, a second laser, a third laser, a first intensity modulator, an unequal-arm interference module and a second intensity modulator, the first laser is connected with the first intensity modulator, the first intensity modulator is respectively connected with the second laser and the third laser, the second laser and the third laser are respectively connected with the unequal-arm interference module, and the unequal-arm interference module is connected with the second intensity modulator. The utility model discloses a time-phase high-speed quantum key coding system based on injection locking, and the system employs the injection locking technology to enable the energy of pulse optical signals emitted by a second laser and a third laser to be more concentrated, thereby enabling the line width to be narrower. And the noise and jitter of the output pulse optical signal are smaller, so that the pulse quality is better, the system is more stable, the code rate is higher, and high-speed coding can be really realized.

Description

Technical Field

[0001] The utility model relates to the technical field of quantum secure communication, and in particular to a time-phase high-speed quantum key encoding system based on injection locking. Background Art

[0002] Quantum Key Distribution (QKD) uses the characteristics of quantum mechanics to ensure the security of communications. The communicating parties encrypt and decrypt messages by generating and sharing a random security key.

[0003] In the existing QKD system, time-phase coding is one of the more common QKD coding schemes, which generally includes phase coding, time coding, entangled state preparation, vacuum state preparation and quantum state preparation processes, so devices such as intensity modulators and phase modulators are required.

[0004] However, on the one hand, due to the technical limitations of optical devices, the light sources, intensity modulators and phase modulators used for quantum key distribution have low working accuracy and large errors when applying driving signals with frequencies exceeding gigahertz (GHz), making it difficult to meet the high-precision requirements for entrapped state preparation and phase encoding, resulting in a low coding rate. On the other hand, in existing time-phase quantum key encoding devices, the noise and jitter of the pulse light signal output by the laser are relatively large, which also leads to a low coding rate.

[0005] Therefore, the existing time-phase quantum key encoding device is difficult to achieve truly high-speed encoding due to its low coding rate. Utility Model Content

[0006] In order to solve the problem of low coding rate of the existing time-phase quantum key coding device, the utility model proposes a time-phase high-speed quantum key coding system based on injection locking.

[0007] In order to achieve the above purpose, the technical solution adopted by the utility model is as follows:

[0008] A time-phase high-speed quantum key encoding system based on injection locking comprises a first laser, a second laser, a third laser, a first intensity modulator, an unequal-arm interference module and a second intensity modulator;

[0009] The output end of the first laser is connected to the input end of the first intensity modulator, the first intensity modulator is connected to the second laser and the third laser respectively, the output end of the second laser and the output end of the third laser are respectively connected to the input end of the unequal-arm interference module, and the output end of the unequal-arm interference module is connected to the input end of the second intensity modulator.

[0010] In the above scheme, the injection locking technology is used to make the energy of the pulse light signal emitted by the second laser and the third laser more concentrated, so the line width is narrower; and the noise and jitter of the pulse light signal output by the second laser and the third laser are smaller, so the pulse quality is better, thereby making the system more stable and the coding rate higher, and can truly realize high-speed encoding.

[0011] Preferably, it also includes a main control module; the control input end of the first laser, the control input end of the first intensity modulator, the control input end of the unequal-arm interference module, and the control input end of the second intensity modulator are respectively connected to different output ends of the main control module.

[0012] Preferably, the main control module includes a quantum random number generator and an FPGA; the output end of the quantum random number generator is connected to the input end of the FPGA, and the control input end of the first laser, the control input end of the first intensity modulator, the control input end of the unequal-arm interference module, and the control input end of the second intensity modulator are respectively connected to different output ends of the FPGA.

[0013] Preferably, it also includes an adjustable attenuator; the control input end of the adjustable attenuator is connected to the first output end of the FPGA, and the output end of the first laser is connected to the input end of the first intensity modulator through the adjustable attenuator.

[0014] Preferably, it further comprises a first beam splitter; the first intensity modulator is connected to the second laser and the third laser respectively through the first beam splitter.

[0015] Preferably, it further comprises a first circulator and a second circulator;

[0016] The first port of the first circulator and the first port of the second circulator are respectively connected to different output ends of the first beam splitter, the second port of the first circulator is connected to the second laser, the second port of the second circulator is connected to the third laser, and the third port of the first circulator and the third port of the second circulator are respectively connected to different input ends of the unequal-arm interference module.

[0017] Preferably, the unequal-arm interference module includes a second beam splitter, a first phase modulator, a second phase modulator and a beam combiner;

[0018] The third port of the first circulator and the third port of the second circulator are respectively connected to different input ends of the second beam splitter, the input end of the first phase modulator and the input end of the second phase modulator are respectively connected to different output ends of the second beam splitter, the output end of the first phase modulator and the output end of the second phase modulator are respectively connected to different input ends of the beam combiner, and the output end of the beam combiner is connected to the input end of the second intensity modulator;

[0019] The control input terminal of the first phase modulator is connected to the second output terminal of the FPGA, and the control input terminal of the second phase modulator is connected to the third output terminal of the FPGA.

[0020] Preferably, a filter is further included, and the output end of the second intensity modulator is connected to the input end of the filter.

[0021] Preferably, the first beam splitter is a 50:50 beam splitter.

[0022] Preferably, one of the first phase modulator and the second phase modulator is arranged on the long arm of the unequal-arm interference module, and the other is arranged on the short arm of the unequal-arm interference module.

[0023] Beneficial technical effects of the utility model:

[0024] The utility model provides a time-phase high-speed quantum key coding system based on injection locking, which adopts the injection locking technology to make the energy of the pulse light signal emitted by the second laser and the third laser more concentrated, so the line width is narrower; and the noise and jitter of the pulse light signal output by the second laser and the third laser are smaller, so the pulse quality is better, so that the system is more stable and the coding rate is higher, and high-speed coding can be truly realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the overall module connection of the utility model;

[0026] Among them: 11, the first laser; 12, the second laser; 13, the third laser; 2, the first intensity modulator; 3, the unequal-arm interference module; 31, the second beam splitter; 32, the first phase modulator; 33, the second phase modulator; 34, the beam combiner; 4, the second intensity modulator; 5, the main control module; 51, the quantum random number generator; 6, the adjustable attenuator; 7, the first beam splitter; 81, the first circulator; 82, the second circulator; 9, the filter. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the utility model more clearly understood, the utility model is further described in detail below in conjunction with embodiments, but the scope of protection claimed in the utility model is not limited to the following specific embodiments. Example

[0028] like Figure 1 As shown, a time-phase high-speed quantum key encoding system based on injection locking includes a first laser 11, a second laser 12, a third laser 13, a first intensity modulator 2, an unequal-arm interference module 3 and a second intensity modulator 4;

[0029] The output end of the first laser 11 is connected to the input end of the first intensity modulator 2, the first intensity modulator 2 is connected to the second laser 12 and the third laser 13 respectively, the output end of the second laser 12 and the output end of the third laser 13 are connected to the input end of the unequal-arm interference module 3 respectively, and the output end of the unequal-arm interference module 3 is connected to the input end of the second intensity modulator 4.

[0030] In the specific implementation process, the injection locking technology is used to make the energy of the pulse light signal emitted by the second laser 12 and the third laser 13 more concentrated, so the line width is narrower; and the noise and jitter of the pulse light signal output by the second laser 12 and the third laser 13 are smaller, so the pulse quality is better, thereby making the system more stable and the coding rate higher, and can truly realize high-speed encoding.

[0031] More specifically, it also includes a main control module 5; the control input end of the first laser 11, the control input end of the first intensity modulator 2, the control input end of the unequal-arm interference module 3, and the control input end of the second intensity modulator 4 are respectively connected to different output ends of the main control module 5.

[0032] More specifically, the main control module 5 includes a quantum random number generator 51 and an FPGA; the output end of the quantum random number generator 51 is connected to the input end of the FPGA, and the control input end of the first laser 11, the control input end of the first intensity modulator 2, the control input end of the unequal-arm interference module 3, and the control input end of the second intensity modulator 4 are respectively connected to different output ends of the FPGA.

[0033] More specifically, it also includes an adjustable attenuator 6 ; the control input end of the adjustable attenuator 6 is connected to the first output end of the FPGA, and the output end of the first laser 11 is connected to the input end of the first intensity modulator 2 through the adjustable attenuator 6 .

[0034] More specifically, it also includes a first beam splitter 7; the first intensity modulator 2 is connected to the second laser 12 and the third laser 13 respectively through the first beam splitter 7.

[0035] More specifically, it also includes a first circulator 81 and a second circulator 82;

[0036] The first port of the first circulator 81 and the first port of the second circulator 82 are respectively connected to different output ends of the first beam splitter 7, the second port of the first circulator 81 is connected to the second laser 12, the second port of the second circulator 82 is connected to the third laser 13, and the third port of the first circulator 81 and the third port of the second circulator 82 are respectively connected to different input ends of the unequal-arm interference module 3.

[0037] More specifically, the unequal-arm interference module 3 includes a second beam splitter 31, a first phase modulator 32, a second phase modulator 33 and a beam combiner 34;

[0038] The third port of the first circulator 81 and the third port of the second circulator 82 are respectively connected to different input ends of the second beam splitter 31, the input end of the first phase modulator 32 and the input end of the second phase modulator 33 are respectively connected to different output ends of the second beam splitter 31, the output end of the first phase modulator 32 and the output end of the second phase modulator 33 are respectively connected to different input ends of the beam combiner 34, and the output end of the beam combiner 34 is connected to the input end of the second intensity modulator 4;

[0039] The control input terminal of the first phase modulator 32 is connected to the second output terminal of the FPGA, and the control input terminal of the second phase modulator 33 is connected to the third output terminal of the FPGA.

[0040] More specifically, a filter 9 is further included, and the output end of the second intensity modulator 4 is connected to the input end of the filter 9 .

[0041] More specifically, the first beam splitter 7 is a 50:50 beam splitter.

[0042] More specifically, one of the first phase modulator 32 and the second phase modulator 33 is disposed on the long arm of the unequal-arm interference module 3 , and the other is disposed on the short arm of the unequal-arm interference module 3 .

[0043] In the specific implementation process, the quantum random number generator 51 outputs a quantum random number to the FPGA, and the FPGA generates a trigger control signal output to the first laser 11 based on the quantum random number. The first laser 11 outputs the corresponding laser after receiving the trigger control signal sent by the FPGA. The laser output from the first laser 11 is adjusted in optical power through the adjustable attenuator 6, and the attenuation value of the adjustable attenuator 6 is controlled and adjusted by the FPGA. The laser output from the adjustable attenuator 6 enters the first intensity modulator 2 for entrapped state preparation; the first intensity modulator 2 is adjusted and controlled by the FPGA. In the entrapped state preparation process, the first intensity modulator 2 is used for phase encoding, entrapped state time encoding, and vacuum state encoding optical pulse intensity suppression (in this embodiment, the intensity of the optical pulse is attenuated to half of the original), while the intensity of the optical pulse of signal state time encoding remains unchanged. The laser output from the first intensity modulator 2 is divided equally by the first beam splitter 7 at a ratio of 50:50 to form two equal laser beams, one of which is output to the first port of the first circulator 81, and the other is output to the first port of the second circulator 82, so that the optical pulse emitted by the first laser 11 is injection-locked to the second laser 12 and the third laser 13, so that the second laser 12 and the third laser 13 output optical pulses with good consistency.

[0044] Among them, the light pulses emitted by the second laser 12 and the third laser 13 have the same waveform as the light pulses of the first laser 11, and the light emission mode of the second laser 12 and the third laser 13 adopts the injection locking technology; the injection locking technology is to inject the seed light pulses emitted by the first laser 11 into the resonant cavity gain region of the second laser 12 and the third laser 13, so that the stimulated radiation process makes the same mode as the seed light pulse preferentially start, and other modes are suppressed due to competition, so that the laser outputs a pulse light signal with the same wavelength and phase as the seed light pulse, so that the center wavelength of the pulse light signal output by the second laser 12 and the third laser 13 is locked to the center wavelength of the seed light pulse. The injection locking technology makes the energy of the pulse light signal emitted by the second laser 12 and the third laser 13 more concentrated, so the line width is narrower; and also makes the noise and jitter of the pulse light signal output by the second laser 12 and the third laser 13 smaller, so the pulse quality is better.

[0045] The second beam splitter 31, the first phase modulator 32, the second phase modulator 33 and the beam combiner 34 form an unequal-arm interferometer. The lasers output from the second laser 12 and the third laser 13 enter the second port of the first circulator 81 and the second port of the second circulator 82 respectively. The lasers output from the third port of the first circulator 81 and the third port of the second circulator 82 all enter the second beam splitter 31. The second beam splitter 31 divides the input light into 50:50 equal parts and outputs two equal lasers, one of which enters the first phase modulator 32 for phase modulation, and the other enters the second phase modulator 33 for phase modulation. Among them, the first phase modulator 32 and the second phase modulator 33 are controlled and adjusted by FPGA. The lasers output from the first phase modulator 32 and the second phase modulator 33 are input into the beam combiner 34 to be combined into a beam of light output, thereby completing phase encoding. The laser output from the beam combiner 34 enters the second intensity modulator 4 for time encoding and / or vacuum state preparation, and the second intensity modulator 4 is controlled and adjusted by the FPGA. The optical signal coming out of the second intensity modulator 4 is filtered out through a filter to remove clutter. Among them, the driving signal frequency range of the first laser 11, the first intensity modulator 2, the first phase modulator 32, and the second phase modulator 33 is 625MHZ-1GHZ, and the driving signal range of the second intensity modulator 4 is 1.25Ghz-2Ghz. Example

[0046] The instrument models and parameters used in this embodiment are as follows (they can be adjusted and set according to specific needs in practice):

[0047] The laser uses the 1064nm SLD seed source of Xinwei Optoelectronics. The laser is a standard 10PIN butterfly package with a pulse peak power of 1000mw and a standard single-mode fiber output with good compatibility.

[0048] The attenuator adopts high-speed HVOA, insertion loss: <1dB; dynamic range: >25dB; PDL: 0.1dB; response time: <250ns; input optical power: <500mW; return loss: >55dB;

[0049] The intensity modulator uses the high-speed lithium niobate intensity modulator produced by EOSPACE in the United States, which can provide a rate of 10G to 60G, and has a very wide working bandwidth and ultra-low driving voltage. It also provides a variety of working wavelength models, covering wavelengths of 600nm, 650nm, 700nm, 780nm, 850nm, 980nm, 1060nm, 1310nm, 1550nm, 2000+nm and other options; the product provides ultra-low voltage models, and the half-wave voltage can be selected as 3V or 2.5V. The ultra-low differential loss model can provide an insertion loss of less than 3dB or even 2dB.

[0050] The beam splitter and combiner use a polarization beam combiner (PBC / PBS). The input of the PBC is two polarization-maintaining fibers, which can combine two beams of linearly polarized light into a single-mode fiber at the output end, thereby realizing the function of pump beam combining and providing pump power to make up for the disadvantage of low pump power. At the same time, this device can also be used in reverse to split a beam of non-polarized light into two beams of linearly polarized light with perpendicular polarization directions. The product has the characteristics of low insertion loss, small size, high extinction ratio, high stability and high reliability, and can be used in fiber lasers, fiber sensors, fiber amplifiers, scientific research and testing equipment.

[0051] The circulator uses a polarization-maintaining (PM) fiber circulator, which is an irreversible unidirectional three-port device and is widely used in a large number of optical devices and many occasions. The central wavelength of the PM fiber circulator is 1064, 1310 or 1550 nanometers. The optical circulator is a three-port device, and light can only propagate in one direction. If the signal is input from port 1, it will be output from port 2; and if the signal is input from port 2, it will be output from port 3, and the output loss is very small. When light is input from port 2, the loss is large when it is output from port 1. Similarly, when light is input from port 3, the loss is also large when it is output from ports 1 and 2. The optical circulator is an irreversible optical device. Due to its high isolation, the insertion loss is small. Main parameters: Insertion loss: (dB) ≤ 1.20; Ports and working mode: 3 ports, (Port 1→2, 2→3); Isolation (dB) ≥30; Directivity (dB): ≥40; Return loss (dB): ≥40; Extinction ratio (dB): 20dB; Withstand power (mW): ≤500; Tensile load: 5N; Polarization-dependent loss: 0.1dB; Fiber type: PM1550;

[0052] The phase modulator used is the phase modulator of EOSPACE Company of the United States, with the following main parameters: center wavelength 1064nm; 3dB bandwidth: >10GHz (std), >18GHz (opt); insertion loss: <4 dB (<3 dBopt); RF port Vpi (@ 1GHz): <4v (<3vopt).

[0053] According to the disclosure and teaching of the above specification, the technicians in the field of the utility model can also change and modify the above implementation. Therefore, the utility model is not limited to the specific implementation methods disclosed and described above, and some modifications and changes to the utility model should also fall within the scope of protection of the claims of the utility model. In addition, although some specific terms are used in this specification, these terms are only for convenience and do not constitute any limitation to the utility model.

Claims

1. A time-phase high-speed quantum key encoding system based on injection locking, characterized in that: It includes a first laser, a second laser, a third laser, a first intensity modulator, an unequal-arm interference module, and a second intensity modulator; The output end of the first laser is connected to the input end of the first intensity modulator, the first intensity modulator is connected to the second laser and the third laser respectively, the output end of the second laser and the output end of the third laser are respectively connected to the input end of the unequal-arm interference module, and the output end of the unequal-arm interference module is connected to the input end of the second intensity modulator.

2. A time-phase high-speed quantum key encoding system based on injection locking according to claim 1, characterized in that: It also includes a main control module; the control input end of the first laser, the control input end of the first intensity modulator, the control input end of the unequal-arm interference module, and the control input end of the second intensity modulator are respectively connected to different output ends of the main control module.

3. A time-phase high-speed quantum key encoding system based on injection locking according to claim 2, characterized in that: The main control module includes a quantum random number generator and an FPGA; the output end of the quantum random number generator is connected to the input end of the FPGA, and the control input end of the first laser, the control input end of the first intensity modulator, the control input end of the unequal-arm interference module, and the control input end of the second intensity modulator are respectively connected to different output ends of the FPGA.

4. A time-phase high-speed quantum key encoding system based on injection locking according to claim 3, characterized in that: It also includes an adjustable attenuator; the control input end of the adjustable attenuator is connected to the first output end of the FPGA, and the output end of the first laser is connected to the input end of the first intensity modulator through the adjustable attenuator.

5. A time-phase high-speed quantum key encoding system based on injection locking according to claim 3, characterized in that: It also includes a first beam splitter; the first intensity modulator is connected to the second laser and the third laser respectively through the first beam splitter.

6. A time-phase high-speed quantum key encoding system based on injection locking according to claim 5, characterized in that: Also included is a first circulator and a second circulator; The first port of the first circulator and the first port of the second circulator are respectively connected to different output ends of the first beam splitter, the second port of the first circulator is connected to the second laser, the second port of the second circulator is connected to the third laser, and the third port of the first circulator and the third port of the second circulator are respectively connected to different input ends of the unequal-arm interference module.

7. A time-phase high-speed quantum key encoding system based on injection locking according to claim 6, characterized in that: The unequal-arm interference module includes a second beam splitter, a first phase modulator, a second phase modulator and a beam combiner; The third port of the first circulator and the third port of the second circulator are respectively connected to different input ends of the second beam splitter, the input end of the first phase modulator and the input end of the second phase modulator are respectively connected to different output ends of the second beam splitter, the output end of the first phase modulator and the output end of the second phase modulator are respectively connected to different input ends of the beam combiner, and the output end of the beam combiner is connected to the input end of the second intensity modulator; The control input terminal of the first phase modulator is connected to the second output terminal of the FPGA, and the control input terminal of the second phase modulator is connected to the third output terminal of the FPGA.

8. The time-phase high-speed quantum key encoding system based on injection locking according to claim 1 is characterized in that: A filter is also included, wherein the output terminal of the second intensity modulator is connected to the input terminal of the filter.

9. The time-phase high-speed quantum key encoding system based on injection locking according to claim 5, characterized in that: The first beam splitter is a 50:50 beam splitter.

10. A time-phase high-speed quantum key encoding system based on injection locking according to claim 7, characterized in that: One of the first phase modulator and the second phase modulator is arranged on the long arm of the unequal-arm interference module, and the other is arranged on the short arm of the unequal-arm interference module.

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