Compact local oscillator continuous variable quantum key distribution method and device

Abstract

The invention discloses a compact local oscillator continuous variable quantum key distribution method and device, and the method comprises the steps: introducing continuous light into a chip, splitting the continuous light into two paths of light, loading pilot signals and quantum signals containing quantum keys on the two paths of light, and modulating the two paths of light to obtain I-path light and Q-path light; combining the I-path light and the Q-path light, performing power distribution, distributing a part of signal light containing quantum signals, and outputting the signal light to an optical fiber link; and introducing the local oscillation light and the signal light in the optical fiber link into a chip, carrying out homodyne balance detection to obtain differential current, and outputting the differential current through a radio frequency port of the chip. According to the invention, quantum key receiving and transmitting are integrated on a single chip, other discrete optical elements are not needed, the integration level and stability of the local oscillator continuous variable quantum key distribution technology are effectively improved, and the complexity and cost of the local oscillator continuous variable quantum key distribution technology are reduced.

Description

Technical Field

[0001] The present application relates to the field of quantum communication technologies, and in particular, to a compact local oscillator continuous variable quantum key distribution method and apparatus. Background Art

[0002] In the field of quantum secure communication, quantum key distribution is based on the quantum no-cloning theorem and the uncertainty principle, which ensures the information security of legitimate communication parties at the physical level and plays an important role in fields such as military, finance, government, and enterprises. There are currently two technical routes for quantum key distribution, namely discrete variable and continuous variable, which refer to whether the regular component of the loaded modulation signal is discrete or continuous. Among them, continuous variable quantum key distribution is based on the GG02 protocol. The transmitter can use a coherent light source, and the receiver can use a homodyne or heterodyne balanced detector. The device and equipment are compatible with existing coherent optical communication, and there is no need to use expensive single-photon detectors required by the discrete variable scheme, so the cost of the system will be greatly reduced.

[0003] The local oscillator scheme means that the local oscillator light is directly generated by another laser at the receiver end. The local oscillator light will not be transmitted through the channel to cause crosstalk, and at the same time, the risk of local oscillator light leakage is reduced. However, since the signal light and the local oscillator light come from different lasers, the phase difference between the two will change rapidly. Therefore, a pilot signal needs to be inserted in the middle of the quantum signal to assist in recovering the phase of the quantum signal. The quantum signal and the pilot signal need to be multiplexed in different dimensions to avoid crosstalk. Currently, the technical solutions include time multiplexing, polarization multiplexing, and frequency multiplexing. Among them, the time multiplexing and polarization multiplexing schemes require precise delay control, high extinction ratio pulse chopping, and high extinction ratio polarization beam splitting and combining, so they pose high requirements on the device performance; frequency multiplexing loads the quantum signal and the pilot signal onto different frequency carriers and realizes signal demultiplexing through the digital signal processing process. This scheme can directly modulate continuous light and has the advantages of high modulation rate and simple system.

[0004] However, currently, the transmitter end of the local oscillator continuous variable quantum key distribution system often realizes coherent state modulation through a separate intensity modulator, phase modulator, or IQ modulator, and then controls the modulation variance of the coherent state through an adjustable attenuator. This process not only requires the polarization state in the optical fiber to be stable to avoid optical power fluctuations, but also requires an external photodetector to monitor the modulation variance in real time, increasing the system complexity. Summary of the Invention

[0005] The present application provides a compact local oscillator continuous variable quantum key distribution method and apparatus, which can solve the technical problems of relatively high complexity and cost existing in the current local oscillator continuous variable quantum key distribution technology.

[0006] To achieve the above object, in a first aspect, the present application provides a compact local oscillator continuous variable quantum key distribution method, and the method includes:

[0007] Introduce continuous light into the chip, split it into two paths of light, load a pilot signal and a quantum signal containing a quantum key on both paths of light, and simultaneously modulate the two paths of light to obtain I-path light and Q-path light.

[0008] Combine the I-path light and the Q-path light, and then perform power distribution to allocate a part of the signal light containing the quantum signal and output it to the optical fiber link.

[0009] Introduce the local oscillator light and the signal light in the optical fiber link into the chip, perform homodyne balanced detection to obtain a differential current, and output it through the radio frequency port of the chip.

[0010] Further, in an embodiment, loading a pilot signal and a quantum signal containing a quantum key on both paths of light, and simultaneously modulating the two paths of light to obtain I-path light and Q-path light includes:

[0011] Further divide each path of light into an upper path of light and a lower path of light, and perform phase shift on the upper path of light and the lower path of light of each path of light through a phase shifter.

[0012] Load the quantum signal and the pilot signal at different carrier frequencies onto the upper and lower paths of light of each path of light, adjust the phase difference between the upper and lower paths of light of each path of light through a modulator, and combine them.

[0013] Perform phase control on the combined two paths of signal light to obtain I-path light and Q-path light.

[0014] Further, in an embodiment, combine the I-path light and the Q-path light, and then perform power distribution to obtain two parts of signal light, one part is output through a coupler, and the other part is converted into a monitoring current through a photodetector and output.

[0015] Further, in an embodiment, before the power distribution, the combination of the I-path light and the Q-path light into signal light further includes a step of adjusting the attenuation of the signal light.

[0016] Further, in an embodiment, adjusting the attenuation of the signal light includes:

[0017] Calculate the second modulation variance in real time according to the monitoring current. If the second modulation variance is less than a preset first modulation variance, reduce the signal light attenuation amount; if the second modulation variance is greater than the preset first modulation variance, increase the signal light attenuation amount.

[0018] Further, in an embodiment, the performing power distribution includes:

[0019] The combined signal light is divided into two beams again, phase shifts are performed on the two beams of signal light respectively, and power distribution is performed on the two beams of signal light after phase shift through a 2×2 beam splitter.

[0020] Further, in one embodiment, introducing the local oscillator light and the signal light in the optical fiber link into the chip for homodyne balanced detection to obtain a differential current includes:

[0021] Transmitting the signal light containing quantum signals to the chip through the optical fiber link, and introducing the local oscillator light at the same time.

[0022] Mixing the signal light and the local oscillator light, attenuating and performing optoelectronic conversion on the two mixed beams of signal light to obtain a differential current between the two beams of signal light.

[0023] Further, in one embodiment, the receiving method includes:

[0024] Using a transimpedance amplifier to amplify the differential current and convert it into a voltage signal.

[0025] Performing digital signal processing on the voltage signal to obtain the quantum signal after the recovered phase, and extracting the quantum key therefrom.

[0026] In a second aspect, based on the above compact local oscillator continuous variable quantum key distribution method, the present application provides a quantum key distribution device for a compact local oscillator continuous variable quantum key distribution method, and the device includes:

[0027] A beam splitting module that introduces continuous light into the chip and splits it into two beams of light.

[0028] A modulation module that is used to load a pilot signal and a quantum signal containing a quantum key on both beams of light, and modulate both beams of light to obtain I-channel light and Q-channel light at the same time.

[0029] A beam combining module that is used to combine the I-channel light and the Q-channel light into signal light.

[0030] A power control module that is used to perform power distribution on the combined signal light, distribute a part of the signal light containing quantum signals, and output it to the optical fiber link.

[0031] A balanced detection module that is used to introduce the local oscillator light and the signal light in the optical fiber link into the chip for homodyne balanced detection to obtain a differential current, and output it through the radio frequency port of the chip.

[0032] Further, in one embodiment, the quantum key distribution device further includes:

[0033] A first photodetector that is used to detect the other part of the signal light after power distribution and convert it into a monitoring current for output.

[0034] A first adjustable attenuator, which is used to reduce the signal light attenuation when the second modulation variance calculated by the monitoring current is less than a preset first modulation variance; and increase the signal light attenuation when the second modulation variance is greater than the preset first modulation variance.

[0035] The beneficial effects brought by the technical solution provided by the embodiments of the present application include:

[0036] In the present application, continuous light is introduced into the chip and split into two paths of light. Quantum signals and pilot signals are loaded on both paths of light. The two paths of light are modulated by a modulator, and the phases of the two paths of modulated light are adjusted to obtain I-path light and Q-path light, where the quantum signal contains a quantum key; the I-path light and the Q-path light are combined, and then power is distributed to allocate a part of the signal light containing the quantum signal and output it to the optical fiber link; the local oscillator light and the signal light in the optical fiber link are introduced into the chip for homodyne balanced detection to obtain a differential current, which is output through the radio frequency port of the chip. Quantum key transceiver integration is achieved on a single chip without using other discrete optical components, effectively improving the integration and stability of the local oscillator continuous variable quantum key distribution technology, and reducing the complexity and cost of the local oscillator continuous variable quantum key distribution technology. During the quantum key distribution process, the stability of quantum communication is improved by controlling the optical power.

[0037] Furthermore, the I-path light and the Q-path light are combined, and through power distribution, two parts of signal light are obtained. One part is output through a coupler, and the other part is converted into a monitoring current through a photodetector and output. The modulation variance of the quantum signal can be calculated and adjusted in real time according to the output monitoring current, improving the estimation accuracy of noise in the parameter estimation process and enhancing the reliability and efficiency of quantum communication. Description of the Drawings

[0038] Figure 1 It is a flowchart of the compact local oscillator continuous variable quantum key distribution method according to the embodiments of the present application.

[0039] Figure 2 It is a schematic diagram of the compact local oscillator continuous variable quantum key distribution device according to the embodiments of the present application.

[0040] Figure 3 It is a block diagram of the compact local oscillator continuous variable quantum key distribution device according to the embodiments of the present application. Detailed Embodiments

[0041] To enable those skilled in the art to better understand the solution of this application, the following will clearly and completely describe the technical solution in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of this application.

[0042] To make the objectives, technical solutions, and advantages of this application clearer, the following will further describe the embodiments of this application in detail with reference to the accompanying drawings.

[0043] In a first aspect, an embodiment of this application provides a compact local oscillator continuous variable quantum key distribution method.

[0044] In one embodiment, as shown in Figure 1 the above quantum key distribution method includes:

[0045] S1. Introduce continuous light into the chip, split it into two beams of light, load a pilot signal and a quantum signal containing a quantum key on both beams of light, and simultaneously modulate the two beams of light to obtain an I-channel light and a Q-channel light.

[0046] S2. Combine the I-channel light and the Q-channel light, then perform power distribution, distribute a part of the signal light containing the quantum signal, and output it to the optical fiber link.

[0047] S3. Introduce the local oscillator light and the signal light in the optical fiber link into the chip, perform homodyne balanced detection to obtain a differential current, and output it through the radio frequency port of the chip.

[0048] This embodiment realizes the integration of quantum key transceiver on a single chip without using other discrete optical elements, effectively improving the integration and stability of the local oscillator continuous variable quantum key distribution technology, and reducing the complexity and cost of the local oscillator continuous variable quantum key distribution technology. During the quantum key distribution process, this application improves the stability of quantum communication by controlling the optical power.

[0049] Further, in one embodiment, in the above step S1, as shown in Figure 2 continuous light from the optical fiber is introduced into the chip through a first coupler, and is split into two beams of light (the first beam of light and the second beam of light in this embodiment) through a 1×2 Y-branch. The first coupler can be an end-face coupler with horizontal coupling, a grating coupler with vertical coupling, or other devices that can achieve a coupling effect. The above 1×2 Y-branch can be a 1×2 multimode interferometer structure, or other devices that can achieve optical power splitting.

[0050] Further, in one embodiment, in the above step S1, refer to Figure 2 As shown, pilot signals and quantum signals containing quantum keys are loaded on both paths of light, and at the same time, both paths of light are modulated to obtain I-path light and Q-path light, including:

[0051] S101. Further divide each path of light into an upper path of light and a lower path of light, and perform phase shift on the upper path of light and the lower path of light of each path of light through a phase shifter. Specifically, the first path of light and the second path of light are each divided into an upper path of light and a lower path of light through a 1×2 Y-branch. The upper path of light and the lower path of light of the first path of light are respectively phase-shifted through a first phase shifter, and the upper path of light and the lower path of light of the second path of light are respectively phase-shifted through a second phase shifter.

[0052] S102. Load the quantum signal and the pilot signal A p at different carrier frequencies onto the upper and lower paths of light of each path of light, adjust the phase difference between the upper and lower paths of light of each path of light through a modulator, and perform beam combination through a 2×1 combiner, where the formulas for loading the quantum signal and the pilot signal by the first modulator (RF I ) and the second modulator (RF Q ) are:

[0053] RF I =X I (t)cos(2πω qc t)-X Q (t)sin(2πω qc t)+A p cos(2πω p t),

[0054] RF Q =X I (t)sin(2πω qc t)+X Q (t)cos(2πω qc t)+A p sin(2πω p t),

[0055] In the formula, ω qc is the carrier frequency of the quantum signal, ω p is the carrier frequency of the pilot signal. To meet the Gaussian modulation requirements of continuous variable quantum key distribution, the quantum signal satisfies where X I (t) and X Q (t) both satisfy a Gaussian distribution with a mean of 0 and a standard deviation of 1, and the pilot signal A pis a constant, and its value can be adjusted to control the power of the pilot signal relative to the quantum signal. Specifically, both the upper optical path and the lower optical path of the first optical path are loaded with quantum signals through the first modulator and the pilot signal A p , so that a phase difference is generated between the upper optical path and the lower optical path of the first optical path. Similarly, both the upper optical path and the lower optical path of the second optical path are loaded with quantum signals through the second modulator and the pilot signal A p After that, a phase difference is generated between the upper optical path and the lower optical path of the second optical path.

[0056] S103. Phase modulation is performed on the two combined signal optical paths through a phase shifter to obtain an I-channel optical signal and a Q-channel optical signal with a phase difference of 90°. Specifically, the first combined signal optical path is phase-modulated through a third phase shifter, and the second combined signal optical path is phase-modulated through a fourth phase shifter, so that the first combined signal optical path and the second combined signal optical path after modulation become an I-channel optical signal and a Q-channel optical signal with a phase difference of 90°.

[0057] Preferably, the above phase shifters can use thermo-optic phase shifters, and the modulators can use carrier-depletion modulators.

[0058] In this embodiment, in S101 above, phase shifting is performed on the upper optical path and the lower optical path of each optical path through a phase shifter to control the bias point of each optical path, so that the optical field output after combination when the first modulator and the second modulator have not been modulated in S102 is in an interference cancellation state; in S103 above, phase modulation is performed on the two combined signal optical paths through the third phase shifter and the fourth phase shifter, so that the phase difference between the I-channel optical signal and the Q-channel optical signal is 90°, thereby realizing the modulation of the quadrature components of the optical field.

[0059] Further, in one embodiment, in step S2 above, as shown in Figure 2 , the I-channel optical signal and the Q-channel optical signal are combined, and power distribution is performed on the combined signal optical path of the I-channel optical signal and the Q-channel optical signal, including:

[0060] S201. The I-channel optical signal and the Q-channel optical signal are combined through a 2×1 combiner, and the combined signal optical path is divided into two beams again through a 1×2 splitter, and phase shifting is performed on the two beams of signal optical paths respectively. Specifically, one beam of signal optical path is phase-shifted through a fifth phase shifter, and the other beam of signal optical path is phase-shifted through a sixth phase shifter.

[0061] S202. Power distribution is performed on the two beams of signal optical paths after phase shifting through a 2×2 splitter to obtain two parts of signal optical paths. One part of the signal optical path is output to the optical fiber link through the second coupler, and the other part of the signal optical path is subjected to photoelectric conversion through the first photodetector and converted into a monitoring current output, where the power ratio in the power distribution process is set to 1:K.

[0062] In this embodiment, the above power ratio can be adjusted by means of phase shift, which is mainly used to control the modulation variance of the transmitting end and ensure that the optical power received by the photodetector is within the normal working range.

[0063] Based on the above embodiment, before power distribution, it further includes the step of adjusting the attenuation of the signal light after the combination of the I-channel light and the Q-channel light through a first adjustable attenuator. Specifically:

[0064] According to the above, the power ratio of the two signal lights obtained by phase shifting the two signal lights respectively is 1:K. Let the above monitoring current be I M , the responsivity of the first photodetector is R, and the ratio of the pilot optical power to the quantum signal optical power is M. Thus, the second modulation variance of the transmitting end can be calculated as:

[0065]

[0066] In the formula, h is Planck's constant and v is the frequency of the continuous light.

[0067] Therefore, the second modulation variance of the transmitting end is calculated in real time according to the above monitoring current. If the second modulation variance of the transmitting end is less than the preset first modulation variance, the signal light attenuation amount is reduced; if the second modulation variance is greater than the preset first modulation variance, the signal light attenuation amount is increased.

[0068] In this embodiment, by monitoring the photocurrent in real time, the modulation variance of the quantum signal can be updated in real time, rather than assuming that the modulation variance is a fixed value. When there is a deviation between the modulation variance calculated according to the monitoring current and the preset modulation variance, the attenuation amount of the signal is adjusted through the adjustable attenuator, so that the modulation variance required by the transmitting end can be achieved. Therefore, the estimation accuracy of the over-noise in the parameter estimation process can be improved, thereby improving the reliability and efficiency of quantum communication.

[0069] Further, in one embodiment, in the above step S3, as shown in Figure 2 introducing the local oscillator light and the signal light in the optical fiber link into the chip for homodyne balanced detection to obtain a differential current includes:

[0070] S301. Transmit the signal light containing the quantum signal from the optical fiber link to the chip through a third coupler, and at the same time introduce the local oscillator light into the chip through a fourth coupler.

[0071] S302. Mix the above signal light and the above local oscillator light through a 2×2 beam splitter. If the optical field amplitude of the signal light is A q , the optical field frequency is f q , the optical field amplitude of the local oscillator light is A L , the optical field frequency is f L , then the optical fields of the upper and lower two paths of light after mixing are respectively and

[0072] S303. Attenuate the two mixed optical signals, and convert the attenuated upper and lower optical signals into photocurrents through a photodetector. Specifically, attenuate the intensity of the upper optical signal through a second tunable attenuator, attenuate the intensity of the lower optical signal through a third tunable attenuator, convert the attenuated upper optical signal into an upper photocurrent through a second photodetector, and convert the attenuated lower optical signal into a lower photocurrent through a third photodetector. The upper photocurrent is I 1 , and the lower photocurrent is I 2 . Since the local oscillator light and the signal light come from different lasers, there is a frequency difference. In this case, the differential current between the two optical signals output by the homodyne balanced detector is:

[0073] I 1 -I 2 = 4AqA L cos(2π(fq - f L ))t),

[0074] At this time, the differential current contains the amplitude A q of the signal optical field and the amplitude A L of the local oscillator optical field. The above differential current is led out through a gold wire and output to subsequent devices through a radio frequency port.

[0075] Each of the above tunable attenuators can adopt a carrier injection type PIN structure or a Mach-Zehnder interferometer structure, and the attenuators can be cascaded according to the required attenuation amount.

[0076] In this embodiment, by increasing the optical field intensity of the local oscillator light, the differential current can be amplified, so as to detect weak signals. Since an ideal balanced detector requires the responsivities of the two photodetectors to be the same, a tunable attenuator is provided after the 2×2 beam splitter to compensate for the difference in the responsivities of the two photodetectors.

[0077] In a second aspect, based on the above compact local oscillator continuous variable quantum key distribution method, an embodiment of a compact local oscillator continuous variable quantum key receiving method is provided. The above quantum key receiving method includes:

[0078] A1. Use a transimpedance amplifier to amplify the above differential current, convert it into a voltage signal and detect it with an oscilloscope.

[0079] A2. Perform digital signal processing on the voltage signal, obtain the phase drift amount in the channel from the voltage signal, obtain the restored-phase quantum signal, and extract the quantum key therefrom.

[0080] Further, in one embodiment, in the above step A2, digital signal processing is performed on the voltage signal to obtain the phase drift amount in the channel from the voltage signal, obtain the quantum signal after phase recovery, and extract the quantum key therefrom, including:

[0081] A201. The receiving end performs frequency shift and filtering on the voltage signal to restore the pilot signal and the quantum signal.

[0082] A202. The receiving end divides the restored pilot signal by the pilot signal e before restoration i2πw q t , and the continuous rapid phase change θ fast (t) can be obtained. The rapid phase change mainly comes from the phase noise between the above-mentioned signal light and the above-mentioned local oscillator light.

[0083] A203. The receiving end compensates for the phase drift of the restored quantum signal according to θ fast (t), and calculates the I component and Q component of the quantum signal respectively, so as to obtain the phase of the restored quantum signal, and publicly discloses a part of the phase to the transmitting end through the channel.

[0084] A204. The transmitting end compares the phase of the transmitted quantum signal with the phase publicly disclosed by the receiving end, and calculates the slow phase change θ slow (t) that the receiving end has not compensated yet. The slow phase change mainly comes from the phase uncertainty when collecting light and the instability of the optical fiber in the optical fiber link.

[0085] A205. For the remaining undisclosed phase, the receiving end compensates its phase according to θ fast (t), and the transmitting end compensates its phase according to θ slow (t). Both parties can obtain a set of associated data, which is the quantum key.

[0086] In this embodiment, through the digital signal processing process, the phase drift amount in the channel can be obtained from the voltage signal, so as to restore the correct phase of the quantum signal and realize the extraction of the quantum key for subsequent operations such as data reconciliation, privacy amplification, and privacy enhancement.

[0087] Thirdly, based on the above compact local oscillator continuous variable quantum key distribution method, an embodiment of a compact local oscillator continuous variable quantum key distribution device is provided. See Figure 3 As shown, the above device includes a beam splitting module, a modulation module, a beam combining module, a power control module, and a balanced detection module. Specifically:

[0088] The beam splitting module introduces continuous light into the chip and splits it into two beams of light.

[0089] A modulation module, which is used to load a pilot signal and a quantum signal containing a quantum key on both optical paths, and at the same time modulate the two optical paths to obtain an I-path optical signal and a Q-path optical signal.

[0090] A beam combining module, which is used to combine the I-path optical signal and the Q-path optical signal into a signal optical signal.

[0091] A power control module, which is used to perform power distribution on the combined signal optical signal, allocate a part of the signal optical signal containing the quantum signal, and output it to the optical fiber link.

[0092] A balanced detection module, which is used to introduce a local oscillator optical signal and the signal optical signal in the optical fiber link into the chip, perform homodyne balanced detection, obtain a differential current, and output it through the radio frequency port of the chip.

[0093] Further, in an embodiment, as shown in Figure 2 The above device further includes:

[0094] A first photodetector, which is used to detect the other part of the signal optical signal after power distribution and convert it into a monitoring current for output.

[0095] A second photodetector, which is used to convert the optical field of the upper path signal optical signal in the two mixed signal optical signals into an upper path optical current.

[0096] A third photodetector, which is used to convert the optical field of the lower path signal optical signal in the two mixed signal optical signals into a lower path optical current.

[0097] A first tunable attenuator, which is used to reduce the signal optical signal attenuation when the second modulation variance calculated from the monitoring current is less than a preset first modulation variance; and increase the signal optical signal attenuation when the second modulation variance is greater than the preset first modulation variance.

[0098] A second tunable attenuator, which is used to attenuate the upper path signal optical signal in the two mixed signal optical signals.

[0099] A third tunable attenuator, which is used to attenuate the lower path signal optical signal in the two mixed signal optical signals.

[0100] As shown in Figure 2 and Figure 3 The above beam splitting module can adopt a 1×2 Y-branch. The above modulation module includes a first phase shifter, a second phase shifter, a first modulator, a second modulator, a third phase shifter, and a fourth phase shifter. The above beam combining module can adopt a 2×1 combiner. The above power control module includes a 1×2 beam splitter, a fifth phase shifter, a sixth phase shifter, a 2×2 beam splitter, a second coupler, and a first photodetector. The above balanced detection module includes a 2×2 beam splitter, a second tunable attenuator, a third tunable attenuator, a second photodetector, and a third photodetector.

[0101] The compact local oscillator continuous variable quantum key distribution method proposed in this application has the functions of coherent state encoding, modulation variance monitoring, and balanced detection. It can realize the integration of continuous variable quantum key transceiver on a single chip, and can significantly reduce the complexity and cost of the local oscillator continuous variable quantum key distribution technology.

[0102] It should be noted that the serial numbers of the above embodiments of this application are only for description and do not represent the superiority or inferiority of the embodiments.

[0103] The terms "including" and "having" and any variations thereof in the specification, claims, and above-mentioned drawings of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally further include unlisted steps or units, or may optionally further include other steps or units inherent to these processes, methods, products, or devices. The descriptions of terms such as "first", "second", and "third" are used to distinguish different objects, etc., and do not represent a sequence, nor do they limit that "first", "second", and "third" are different types.

[0104] In the description of the embodiments of this application, words such as "exemplary", "for example", or "for illustration" are used to indicate examples, illustrations, or explanations. Any embodiment or design solution described as "exemplary", "for example", or "for illustration" in the embodiments of this application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the use of words such as "exemplary", "for example", or "for illustration" is intended to present related concepts in a specific manner.

[0105] In the description of the embodiments of this application, unless otherwise specified, " / " means "or". For example, A / B can mean A or B; "and / or" in the text is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of this application, "multiple" means two or more than two.

[0106] In some processes described in the embodiments of this application, there are multiple operations or steps that appear in a specific order. However, it should be understood that these operations or steps may not be executed in the order in which they appear in the embodiments of this application or may be executed in parallel. The serial numbers of the operations are only used to distinguish different operations, and the serial numbers themselves do not represent any execution order. In addition, these processes may include more or fewer operations, and these operations or steps may be executed in sequence or in parallel, and these operations or steps may be combined.

[0107] Through the description of the above embodiments, those skilled in the art can clearly understand that the above-described embodiment methods can be implemented by means of software plus a necessary general hardware platform. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation manner. Based on such an understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art can be embodied in the form of a software product. This computer software product is stored in a storage medium as described above (such as ROM / RAM, magnetic disk, optical disk), and includes several instructions for causing a terminal device to execute the methods described in various embodiments of the present application.

[0108] The above are only the preferred embodiments of the present application, and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present application.

Claims

1. A compact local oscillator continuous variable quantum key distribution method, characterized in that: The method comprises: Introduce continuous light into the chip and split it into two light paths. Load the pilot signal and the quantum signal containing the quantum key on both light paths. Modulate the two light paths to obtain I light path and Q light path. The I-path light and the Q-path light are combined, and then power distribution is performed to distribute a portion of signal light containing quantum signals, and output to the optical fiber link; The local oscillator light and the signal light in the optical fiber link are introduced into the chip, and zero-difference balanced detection is performed to obtain a differential current, which is then output through the RF port of the chip.

2. The compact local oscillator continuous variable quantum key distribution method according to claim 1, characterized in that: A pilot signal and a quantum signal containing a quantum key are loaded on both optical paths, and the two optical paths are modulated to obtain an I optical path and a Q optical path, including: Each light path is further divided into an upstream light path and a downstream light path, and the upstream light path and the downstream light path of each light path are phase-shifted by a phase shifter; The quantum signal and the pilot signal are loaded into the upper and lower beams of each light path at different carrier frequencies, and the phase difference between the upper and lower beams of each light path is adjusted by a modulator, and then the beams are combined; The phases of the two combined signal lights are controlled to obtain I light and Q light.

3. The compact local oscillator continuous variable quantum key distribution method according to claim 1, characterized in that: The I-path light and the Q-path light are combined and then power-distributed to obtain two parts of signal light, one of which is output through a coupler, and the other is converted into a monitoring current output through a photoelectric detector.

4. The compact local oscillator continuous variable quantum key distribution method according to claim 3, characterized in that: The I-path light and the Q-path light are combined into a signal light, and before the power distribution, a step of adjusting the attenuation of the signal light is also included.

5. The compact local oscillator continuous variable quantum key distribution method according to claim 4, characterized in that: Adjusting the attenuation of the signal light includes: The second modulation variance is calculated in real time according to the monitoring current. If the second modulation variance is smaller than the preset first modulation variance, the signal light attenuation is reduced; if the second modulation variance is larger than the preset first modulation variance, the signal light attenuation is increased.

6. The compact local oscillator continuous variable quantum key distribution method according to claim 4, characterized in that: The power distribution comprises: The combined signal light is split into two beams again, the two signal light beams are phase-shifted respectively, and the power of the two signal light beams after the phase shift is distributed through a 2×2 beam splitter.

7. The compact local oscillator continuous variable quantum key distribution method according to claim 1, characterized in that: The method of introducing the local oscillator light and the signal light in the optical fiber link into the chip, performing homodyne balanced detection, and obtaining the differential current includes: The signal light containing the quantum signal is transmitted to the chip via an optical fiber link, and the local oscillator light is introduced at the same time; The signal light and the local oscillator light are mixed, and the two mixed signal lights are attenuated and photoelectrically converted to obtain a differential current between the two signal lights.

8. A quantum key receiving method based on the compact local oscillator continuous variable quantum key distribution method according to any one of claims 1 to 7, characterized in that: The receiving method comprises: Amplifying the differential current using a transimpedance amplifier and converting it into a voltage signal; The voltage signal is digitally processed to obtain a quantum signal after phase restoration, from which the quantum key is extracted.

9. A quantum key distribution device based on the compact local oscillator continuous variable quantum key distribution method according to any one of claims 1 to 7, characterized in that: The device comprises: The beam splitting module introduces continuous light into the chip and splits it into two beams; A modulation module, which is used to load a pilot signal and a quantum signal containing a quantum key on both optical paths, and simultaneously modulate the two optical paths to obtain an I optical path and a Q optical path; A beam combining module, used for combining the I-path light and the Q-path light into a signal light; A power control module is used to distribute the power of the combined signal light, distribute a portion of the signal light containing the quantum signal, and output it to the optical fiber link; The balanced detection module is used to introduce the local oscillator light and the signal light in the optical fiber link into the chip, perform zero-difference balanced detection, obtain the differential current, and output it through the RF port of the chip.

10. The quantum key distribution device of the compact local oscillator continuous variable quantum key distribution method according to claim 9, further comprising: A first photodetector, which is used to detect another part of the signal light after power distribution and convert it into a monitoring current output; The first adjustable attenuator is used to reduce the signal light attenuation when the second modulation variance calculated by the monitoring current is less than the preset first modulation variance; and to increase the signal light attenuation when the second modulation variance is greater than the preset first modulation variance.

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