CN113132096B - High-speed quantum key encoding device and encoding method - Google Patents
High-speed quantum key encoding device and encoding method Download PDFInfo
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- CN113132096B CN113132096B CN201911422828.5A CN201911422828A CN113132096B CN 113132096 B CN113132096 B CN 113132096B CN 201911422828 A CN201911422828 A CN 201911422828A CN 113132096 B CN113132096 B CN 113132096B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
- H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
- H04L9/0852—Quantum cryptography
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/5161—Combination of different modulation schemes
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/54—Intensity modulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/548—Phase or frequency modulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/70—Photonic quantum communication
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
- H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
- H04L9/0852—Quantum cryptography
- H04L9/0858—Details about key distillation or coding, e.g. reconciliation, error correction, privacy amplification, polarisation coding or phase coding
Abstract
The application provides a high-speed quantum key coding device and a coding method, which relate to the technical field of quantum communication, wherein the coding device comprises: a light source adapted to generate light pulses with random phases; a first intensity modulator adapted for decoy state preparation; the unequal arm interferometer is suitable for changing one beam of light pulse generated by the light source into two beams of sub light pulse separated in time; a first phase modulator adapted for phase encoding; a second intensity modulator adapted for time-coding and/or vacuum state preparation; the light source, the first intensity modulator, the unequal arm interferometer and the second intensity modulator are sequentially connected in series; the unequal-arm interferometer comprises a long arm and a short arm, and the first phase modulator is arranged on the long arm or the short arm. The method and the device can realize high-speed quantum key coding exceeding gigahertz with high precision.
Description
Technical Field
The application relates to the technical field of quantum communication, in particular to a high-speed quantum key encoding device and an encoding method.
Background
Quantum key distribution is one of the research hotspots in the field of quantum communication, and with the advance of quantum communication industrialization, the realization of high-speed quantum key distribution has great significance for improving quantum communication performance, increasing user experience and the like.
The high-speed quantum key distribution needs a corresponding high-speed quantum key encoding device, the optical pulse frequency output by a system in the existing encoding device is basically in the order of hundred megahertz (MHz), the high-speed encoding device exceeding gigahertz (GHz) has fewer solutions with great difficulty in implementation, and the main limitation is the matching of some optical devices in the encoding device and the driving signal frequency thereof. The difficulty in implementing the high-frequency and high-amplitude pulse driving signal is high, and the quality of the generated driving signal is not high, for example: the signal consistency and flatness are poor, so that when some optical devices are driven to work by the signal consistency and flatness, the modulation result has large deviation, and finally, the resultant code rate is low.
Time-phase encoding is one of important quantum key distribution encoding schemes, the scheme combines time basis vectors and phase basis vectors, and compared with other encoding schemes, the scheme has many advantages, for example, the time basis vectors are not influenced by the environment, and the stability is good, so the resultant code rate is improved to a certain extent, and in addition, the phase basis vectors can appropriately get rid of the influence of the system on polarization to adapt to a complex external environment.
Fig. 1 shows a simplified prior art apparatus based on time-phase encoding, which generally includes the following procedures: phase encoding, time encoding, decoy state preparation, vacuum state preparation and quantum state preparation. Decoy state preparation, time encoding, and vacuum state preparation typically need to be achieved by an intensity modulator, and phase encoding typically needs to be achieved by a phase modulator. In order to realize high-speed encoding with a system frequency of gigahertz (GHz), the apparatus shown in fig. 1 requires that the driving signal frequencies of the light source, the phase modulator and the intensity modulator all reach a gigahertz (GHz) level, but due to the limitation of technical conditions, the light source, the intensity modulator and the phase modulator used for quantum key distribution in the current market have low working accuracy and large error when applying a driving signal with a frequency exceeding gigahertz (GHz), and cannot meet the requirements of high accuracy in decoy state preparation and phase encoding, and finally the system has a low code rate and cannot be implemented, so that the existing time-phase encoding scheme cannot realize high speed in a true sense.
Disclosure of Invention
The application provides a high-speed quantum key coding device and a coding method, which are used for solving the problem that the high-speed coding exceeding gigahertz (GHz) is difficult to realize in the existing time-phase coding scheme.
A high-speed quantum key encoding device, the encoding device comprising: a light source adapted to generate light pulses with random phases; a first intensity modulator adapted for decoy state preparation; the unequal arm interferometer is suitable for changing one beam of light pulse generated by the light source into two beams of sub light pulse separated in time; a first phase modulator adapted for phase encoding; a second intensity modulator adapted for time-coding and/or vacuum state preparation; the light source, the first intensity modulator, the unequal arm interferometer and the second intensity modulator are sequentially connected in series; the unequal-arm interferometer comprises a long arm and a short arm, and the first phase modulator is arranged on the long arm or the short arm.
Preferably, the encoding device further comprises a real-time stability maintaining system, and the first intensity modulator and the second intensity modulator are respectively connected with the set of real-time stability maintaining system.
Preferably, the encoding device further comprises a filter connected to the second intensity modulator.
Preferably, the encoding apparatus further includes a second phase modulator, the first phase modulator is disposed on the long arm, the second phase modulator is disposed on the short arm, or the first phase modulator is disposed on the short arm, and the second phase modulator is disposed on the long arm.
Preferably, the encoding apparatus further comprises a third intensity modulator, an input end of the third intensity modulator is connected to an output end of the second intensity modulator.
Preferably, the encoding apparatus further includes a second phase modulator and a third intensity modulator, an input end of the third intensity modulator is connected to an output end of the second intensity modulator, the first phase modulator is disposed on the long arm, the second phase modulator is disposed on the short arm, or the first phase modulator is disposed on the short arm, and the second phase modulator is disposed on the long arm.
Preferably, the encoding device further comprises a variable optical attenuator connected in series at an end of the encoding device, the variable optical attenuator being configured to reduce the overall signal strength to an optimal number of photons per pulse.
Preferably, the driving signal frequency of the light source, the first intensity modulator and the first phase modulator is the same, and the driving signal frequency of the second intensity modulator is twice the driving signal frequency of the light source.
Preferably, the driving signal frequency of the light source, the first intensity modulator and the first phase modulator is 10MHz to 1GHz, and the driving signal frequency of the second intensity modulator is 20MHz to 2 GHz.
Preferably, the driving signal frequency of the second phase modulator is 10MHz to 1GHz, and the driving signal frequency of the second phase modulator is the same as the driving signal frequency of the light source.
Preferably, the driving signal frequency of the third intensity modulator is 20 MHz-2 GHz, and the driving signal frequency of the third intensity modulator is twice the light source driving signal frequency.
Preferably, the light source is a periodic light pulse generating light source.
A high-speed quantum key coding method is applied to a high-speed quantum key coding device, and comprises the following steps: generating a phase-random light pulse using a light source; performing decoy state preparation, and attenuating the intensity of the optical pulse for preparing the decoy state by using a first intensity modulator; performing phase encoding, changing one beam of light pulse generated by a light source into two beams of first sub-light pulses separated in time by using an unequal arm interferometer, and adjusting the phase difference of the two beams of first sub-light pulses by using a first phase modulator to enable the phase difference of the two beams of first sub-light pulses after being combined to be 0 or pi; and performing time encoding and/or vacuum state preparation, and using a second intensity modulator to extinguish one of the two first sub-light pulses for time encoding and/or extinguish two of the two first sub-light pulses for vacuum state encoding.
Preferably, the method further comprises a re-extinction step of re-extinction of the sub-light pulses extinguished by the second intensity modulator using a third intensity modulator.
Preferably, the driving signal frequency of the light source, the first intensity modulator and the first phase modulator is the same, and the driving signal frequency of the second intensity modulator is twice the driving signal frequency of the light source.
According to the technical scheme provided by the application, a brand-new high-speed quantum key coding device and a coding method are provided, the decoy state preparation process with high precision requirement is arranged before the optical pulse beam splitting process, so that the first intensity modulator for preparing the decoy state does not need the driving signal frequency of gigahertz level, namely the driving frequency of the first intensity modulator is reduced, and the high-precision decoy state preparation process in the high-speed scheme is implemented; meanwhile, by the high-speed encoding device and the encoding method, a driving signal with lower frequency is also adopted in the optical pulse preparation and phase encoding process with higher precision requirement, and low-frequency driving is better matched with related optical devices, so that the related optical devices can achieve higher accuracy; in addition, the time coding and the vacuum state preparation process which have relatively low precision requirement are arranged after the light pulse beam splitting process, and a driving signal with higher frequency is adopted to cooperate with the system to complete high-speed coding. In addition, two intensity modulators can be adopted for time coding and/or vacuum state preparation, so that the precision of time coding and vacuum state preparation can be further improved, and the precision of integral high-speed coding is further ensured.
Drawings
In order to more clearly explain the technical solution of the present application, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious to those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a simplified prior art time-phase based encoding apparatus;
FIG. 2 is a schematic diagram of a high-speed quantum key encoding apparatus according to the present application;
FIG. 3 is a schematic diagram of a high-speed quantum key encoding apparatus including a real-time stability maintenance system according to the present application;
FIG. 4 is a schematic diagram of a high-speed quantum key encoding apparatus including a filter according to the present application;
FIG. 5 is a schematic diagram of a high-speed quantum key encoding apparatus including two phase modulators according to the present application;
FIG. 6 is a schematic diagram of a high-speed quantum key encoding apparatus including three intensity modulators according to the present application;
FIG. 7 is a schematic diagram of a high-speed quantum key encoding apparatus including two phase modulators and three intensity modulators according to the present application;
FIG. 8 is a schematic diagram of a high-speed quantum key encoding device incorporating a variable optical attenuator according to the present application;
FIG. 9 is a schematic diagram of the real-time stability maintenance system of the present application;
FIG. 10 is a schematic flow chart of the method of the present application;
fig. 11 is a schematic diagram of each encoding state in the present application.
Detailed Description
The technical solutions of the present invention will be described in detail with reference to the accompanying drawings and specific embodiments, it should be understood that these embodiments are merely illustrative of the present invention and are not intended to limit the scope of the present invention, and various equivalent modifications of the present invention by those skilled in the art after reading the present invention fall within the scope of the appended claims.
It will be understood that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a unique embodiment.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The invention provides a high-speed quantum key coding device and a coding method, which can solve the problem that the high-speed coding exceeding gigahertz (GHz) is difficult to realize in the existing time-phase coding scheme.
Optical connection in this application means that two or more optical devices are connected by optical fiber or polarization maintaining optical fiber, and of course, connecting optical devices by other optical means is also called optical connection.
Referring to fig. 2, a high-speed quantum key encoding apparatus provided in an embodiment of the present application includes: a light source adapted to generate light pulses with random phases; a first intensity modulator IM1, adapted for trick mode preparation; the unequal arm interferometer is suitable for changing one beam of light pulse generated by the light source into two beams of sub light pulse separated in time; a first phase modulator PM1 adapted for phase encoding; a second intensity modulator IM2, suitable for time coding and/or vacuum state preparation; the light source, the first intensity modulator IM1, the unequal arm interferometer and the second intensity modulator IM2 are sequentially connected in series; the unequal-arm interferometer includes a long arm and a short arm, and the first phase modulator PM1 is disposed on the long arm or the short arm. Specifically, the output of the light source is connected to the input of a first intensity modulator IM1, the output of the first intensity modulator IM1 is connected to an unequal arm interferometer, the output of the unequal arm interferometer is connected to the input of a second intensity modulator IM2, the first phase modulator PM1 is connected in series to the long arm or the short arm of the unequal arm interferometer, the unequal arm interferometer comprises a long arm, a short arm, a first beam splitter PMBS1 and a second beam splitter PMBS2, the output of the first intensity modulator IM1 is connected to the input of the first beam splitter PMBS1, the output of the second beam splitter PMBS2 is connected to the input of the second intensity modulator IM2, and the second intensity modulator IM2 outputs the encoded light pulses.
In one possible embodiment, the splitting ratio of the first beam splitter PMBS1 to the second beam splitter PMBS2 in the unequal arm interferometer is 50: 50 (actually, the optical path can be finely adjusted in the vicinity of 50: 50), the optical path of the long arm in the unequal arm interferometer is greater than that of the short arm, the first beam splitter PMBS1 is used for splitting one light pulse emitted by the light source into two first sub-light pulses and outputting the two first sub-light pulses through different light paths, and the second beam splitter PMBS2 is used for combining the two first sub-light pulses respectively passing through the long arm and the short arm and outputting the combined light pulses.
The light source is a periodic light pulse generating light source for generating periodic light pulses and random phase light pulses, and those skilled in the art can recognize that any light source form capable of satisfying the above coding requirement may be used, for example, a chopped mode light source (a chopped mode light source is formed by sequentially connecting a laser, an intensity modulator and a phase modulator in series), other laser structures such as a pulse injection locked laser, etc., and a light source with an internal modulation function such as an electro-absorption modulation laser, where the intensity of the light pulse emitted by the internal modulation light source is already partially intensity-modulated, may also be used.
Referring to fig. 3, the high-speed quantum key encoding apparatus of the present application may further include a real-time stability maintaining system, and the first intensity modulator IM1 and the second intensity modulator IM2 are respectively connected to a set of real-time stability maintaining systems. Taking the real-time stability maintaining system connected to the first intensity modulator IM1 as an example, as shown in fig. 9, specifically, the real-time stability maintaining system includes a light intensity monitor, a wavelength division device, a reference light source and a third beam splitter PMBS3, where the reference light source emits a reference light and the reference light is only used for stability maintenance, so that the real-time stability maintaining system of the present application can perform stability maintenance work without affecting communication efficiency, as shown in fig. 9, a light pulse emitted by the light source and the reference light output a combined light through the third beam splitter PMBS3, the combined light is sent to the first intensity modulator IM1, the first intensity modulator IM1 is used for modulating the combined light and outputting a modulated light, the modulated light is sent to the wavelength division device, the wavelength division device is used for splitting the modulated light, and obtaining modulated light pulses, i.e., the light pulse and the modulated reference light emitted by the light source, the modulated light pulse is transmitted to the unequal arm interferometer, the modulated reference light is transmitted to the light intensity monitor, and the light intensity monitor is used for feeding back and adjusting the working point voltage of the first intensity modulator IM1 in real time according to the measured average light power value of the modulated reference light, so that the light intensity of the output modulated light pulse meets the system requirement. The wavelength division device may be a dense wavelength division multiplexer or other common wavelength division devices as long as it can split the modulated light.
The high-speed quantum key encoding apparatus may further include a filter, as shown in fig. 4, connected to the second intensity modulator IM2 for filtering the encoded optical pulses.
In a possible embodiment, referring to fig. 5, the high speed encoding apparatus may further include a second phase modulator PM2, where the first phase modulator PM1 is disposed on the long arm of the unequal arm interferometer and the second phase modulator PM2 is disposed on the short arm of the unequal arm interferometer, or the first phase modulator PM1 is disposed on the short arm of the unequal arm interferometer and the second phase modulator PM2 is disposed on the long arm of the unequal arm interferometer. The second phase modulator PM2 is also suitable for phase encoding and cooperates with the first phase modulator PM1 to modulate the phase of the two first sub-optical pulses separately.
In yet another possible embodiment, referring to fig. 6, the high-speed quantum key encoding apparatus may further include a third intensity modulator IM3, an input terminal of the third intensity modulator IM3 being connected to an output terminal of the second intensity modulator IM 2. The third intensity modulator IM3 is also suitable for time-coding and/or vacuum state preparation, and the third intensity modulator IM3 may again extinguish the sub-light pulses extinguished by the second intensity modulator.
Referring to fig. 7, the high-speed quantum key encoding apparatus may further include a second phase modulator PM2 and a third intensity modulator IM3, wherein an input terminal of the third intensity modulator IM3 is connected to an output terminal of the second intensity modulator IM2, the first phase modulator PM1 is disposed on a long arm of the unequal-arm interferometer, and the second phase modulator PM2 is disposed on a short arm of the unequal-arm interferometer, or the first phase modulator PM1 is disposed on a short arm of the unequal-arm interferometer, and the second phase modulator PM2 is disposed on a long arm of the unequal-arm interferometer. At this time, the functions of the second phase modulator PM2 and the third intensity modulator IM3 are the same as the functions of the second phase modulator PM2 and the third intensity modulator IM3 in the above-described embodiment.
Referring to fig. 8, the high-speed quantum key encoding device may further include a variable optical attenuator ATT connected in series at the end of the encoding device, and the variable optical attenuator ATT may be used to reduce the overall signal intensity to the optimal number of photons per pulse instead of the intensity modulator to complete quantum state preparation.
On the basis of the embodiment shown in fig. 2, the high-speed quantum key encoding apparatus may have various implementations, and the encoding apparatus of the embodiment shown in fig. 2 may further include any combination of one or more of a real-time stability maintaining system, a filter, a second phase modulator PM2, a third intensity modulator IM3, and a variable optical attenuator ATT. For example, in a possible implementation manner, based on the embodiment shown in fig. 2, the high-speed quantum key encoding apparatus may further include a real-time multidimensional system, a filter, a second phase modulator PM2, a third intensity modulator IM3, a variable optical attenuator ATT, a light source, a first intensity modulator IM1, an unequal arm interferometer, a second intensity modulator IM2, a third intensity modulator IM3, a filter, and a variable optical attenuator ATT, which are connected in series in sequence, and the variable optical attenuator ATT outputs a final encoded light pulse, wherein, the first intensity modulator IM1, the second phase modulator PM2 and the third intensity modulator IM3 are respectively connected with a set of real-time stability maintaining system, the first phase modulator PM1 is arranged on the long arm of the unequal arm interferometer, and the second phase modulator PM2 is arranged on the short arm of the unequal arm interferometer, alternatively, the first phase modulator PM1 is disposed on the short arm of the interferometer and the second phase modulator PM2 is disposed on the long arm of the interferometer; the above is an embodiment containing more optical devices, and one or more of the real-time stabilizer system, the filter, the second phase modulator PM2, the third intensity modulator IM3, and the variable optical attenuator ATT may be subtracted to form other embodiments while the connection relationship remains unchanged.
In the above embodiments, the driving signal frequency of the light source, the first intensity modulator IM1 and the first phase modulator PM1 are the same, and the driving signal frequency of the second intensity modulator IM2 is twice as high as the light source driving signal frequency; the frequency ranges of the driving signals of the light source, the first intensity modulator IM1 and the first phase modulator PM1 are 10 MHz-1 GHz, and the frequency of the driving signal of the second intensity modulator IM2 is 20 MHz-2 GHz. In the embodiment including the second phase modulator PM2, the driving signal frequency of the second phase modulator is the same as the driving signal frequency of the light source, and the driving signal frequency of the second phase modulator PM2 is 10MHz to 1 GHz. In the embodiment including the third intensity modulator IM3, the driving signal frequency of the third intensity modulator IM3 is 20MHz to 2GHz, and the driving signal frequency of the third intensity modulator IM3 is twice the light source driving signal frequency. Specifically, one optical pulse emitted by the light source passes through the unequal arm interferometer and then becomes two first sub optical pulses after being combined, the frequency of the optical pulse becomes twice that before, and accordingly, the driving signal frequencies of the second intensity modulator IM2 and the third intensity modulator IM3 after the unequal arm interferometer are twice that of the driving signal frequencies of the light source, the first intensity modulator IM1, the first phase modulator PM1 and the second phase modulator PM 2; the drive signal frequencies of the light source, the first intensity modulator IM1, the first phase modulator PM1 and the second phase modulator PM2 are identical, and the drive signal frequencies of the second intensity modulator IM2 and the third intensity modulator IM3 are identical. In order to make the frequency of the optical pulses finally emitted by the encoding device exceed gigahertz to realize high-speed quantum key encoding, it is preferable that the driving signal frequencies of the light source, the first intensity modulator IM1, the first phase modulator PM1 and the second phase modulator PM2 are 625MHz to 1GHz, and correspondingly, the driving signal frequencies of the second intensity modulator and the third intensity modulator are 1.25GHz to 2 GHz.
A high-speed quantum key encoding method applied to a high-speed quantum key encoding device, specifically, as shown in fig. 10 and 11, the method includes the steps of:
in step 101, a light source is used to generate light pulses with random phases.
In step 102, decoy state preparation is performed, and the intensity of the light pulse used to prepare the decoy state is attenuated using the first intensity modulator. Specifically, the optical pulses for phase encoding, decoy state time encoding, and vacuum state encoding may be intensity-attenuated by the first intensity modulator IM1, and as shown in fig. 11, in the decoy state preparation process, the first intensity modulator IM1 may intensity-suppress the optical pulses for phase encoding, decoy state time encoding, and vacuum state encoding while the intensity of the optical pulses for signal state time encoding remains unchanged, and preferably, may attenuate the intensity of the optical pulses for phase encoding, decoy state time encoding, and vacuum state encoding to half of the original intensity.
In step 103, phase encoding is performed, one optical pulse generated by the light source is changed into two temporally separated first sub optical pulses by using an unequal arm interferometer, and the phase difference between the two first sub optical pulses is adjusted by using a first phase modulator so that the phase difference between the two first sub optical pulses after being combined is 0 or pi. In a possible embodiment, the first phase modulator PM1 may be adjusted such that the phase of a bundle of first sub-optical pulses passing through the first phase modulator PM1 is changed by pi, or the first phase modulator PM1 may be adjusted such that the phase of a bundle of first sub-optical pulses passing through the first phase modulator PM1 is changed by 0.
In step 104, time encoding and/or vacuum state preparation is performed, and one of the two first sub-optical pulses for time encoding and/or both of the two first sub-optical pulses for vacuum state encoding are extinguished by using a second intensity modulator. Specifically, referring to fig. 11, using the second intensity modulator IM2 to extinguish one of the two first sub-optical pulses for time coding, a time signal with a time bin of 1 or a time bin of 0 can be obtained, and in combination with the signal state and the spoofing state, 4 time codes, that is, a time code with a signal state time bin of 1, a time code with a signal state time bin of 0, a time code with a spoofing state time bin of 1, and a time code with a spoofing state time bin of 0, are obtained in total; two of the two first sub-light pulses used for the vacuum state encoding were extinguished using the second intensity modulator IM 2.
In the high-speed quantum key encoding method, a re-extinction step may be further included, in which the sub-optical pulses that are extinguished by the second intensity modulator are re-extinguished using a third intensity modulator. Since the second intensity modulator IM2 does not have high precision and large error in the light pulse modulation when a driving signal having a frequency exceeding gigahertz (GHz) is applied to the second intensity modulator IM2, that is, the extinction does not achieve the required precision, the third intensity modulator IM3 may be provided to further perform the extinction in order to improve the extinction precision. Referring to fig. 11, during time coding and vacuum preparation, the third intensity modulator IM3 may perform extinction again on the sub-optical pulses extinguished by the second intensity modulator IM2 to achieve the required extinction accuracy, thereby ensuring the accuracy of the overall high-speed coding.
Those skilled in the art will recognize that in implementations, the two processes of time coding and vacuum preparation may be performed by one intensity modulator, or both intensity modulators, with one process being performed by one intensity modulator and the other process being performed by the other intensity modulator.
In the high-speed quantum key encoding method, the two phase modulators may be used to modulate the phase difference between the two first sub-optical pulses, so that the phase difference between the two combined first sub-optical pulses is 0 or pi. For example, the first phase modulator PM1 may be adjusted to change the phase of one first sub-optical pulse passing through the first phase modulator PM1 by pi/2, and the second phase modulator PM2 may be adjusted to change the phase of another first sub-optical pulse passing through the second phase modulator PM2 by-pi/2, and those skilled in the art may adopt various phase modulation methods to make the phase difference between the two combined first sub-optical pulses be 0 or pi, which is only an example and is not a specific limitation herein.
In the high-speed quantum key encoding method, the quantum state may be prepared by using a variable optical attenuator ATT, and the quantum state signal may be obtained by reducing the overall optical pulse signal intensity to the optimal average photon number per optical pulse by using the variable optical attenuator ATT.
In the high-speed quantum key encoding method, a filtering step may be added to filter the optical pulses output from the intensity modulator to remove the influence of noise.
Preferably, in the high-speed quantum key encoding method, the driving signal frequencies of the light source, the first intensity modulator and the first phase modulator are the same, and the driving signal frequency of the second intensity modulator is twice the driving signal frequency of the light source, so as to ensure the accuracy of the overall high-speed encoding.
Those skilled in the art can recognize that the high-speed quantum key encoding apparatus provided by the present application is suitable for various encoding protocols, including but not limited to encoding schemes based on the decoy BB84 protocol, RFIQKD protocol, three-state protocol, simplified BB84 protocol, MDIQKD protocol, etc.
It should be noted that, in the description of the present application, the terms "first", "second", and the like are used for descriptive purposes only and for distinguishing similar objects, and no precedence between the two is intended or should be construed to indicate or imply relative importance. In addition, in the description of the present application, "a plurality" means two or more unless otherwise specified.
The present application has been described in detail with reference to specific embodiments and illustrative examples, but the description is not intended to limit the application. Those skilled in the art will appreciate that various equivalent substitutions, modifications or improvements may be made to the presently disclosed embodiments and implementations thereof without departing from the spirit and scope of the present disclosure, and these fall within the scope of the present disclosure. The protection scope of this application is subject to the appended claims.
Claims (15)
1. A high-speed quantum key encoding apparatus, the encoding apparatus comprising:
a light source adapted to generate light pulses with random phases;
a first intensity modulator adapted for decoy state preparation;
the unequal arm interferometer is suitable for changing one beam of light pulse generated by the light source into two beams of sub light pulse separated in time;
a first phase modulator adapted for phase encoding;
a second intensity modulator adapted for time-coding and/or vacuum state preparation;
the light source, the first intensity modulator, the unequal arm interferometer and the second intensity modulator are sequentially connected in series;
the unequal-arm interferometer comprises a long arm and a short arm, and the first phase modulator is arranged on the long arm or the short arm.
2. The high-speed quantum key encoder of claim 1, wherein the encoder further comprises a real-time stability maintaining system, and the first intensity modulator and the second intensity modulator are respectively connected to a set of the real-time stability maintaining system.
3. The high-speed quantum key encoding apparatus of claim 1, wherein the encoding apparatus further comprises a filter coupled to the second intensity modulator.
4. The high-speed quantum key encoding apparatus of claim 1, wherein the encoding apparatus further comprises a second phase modulator, the first phase modulator is disposed on the long arm, the second phase modulator is disposed on the short arm, or the first phase modulator is disposed on the short arm, and the second phase modulator is disposed on the long arm.
5. The high-speed quantum key encoding apparatus of claim 1, wherein the encoding apparatus further comprises a third intensity modulator, an input of the third intensity modulator being connected to an output of the second intensity modulator.
6. The apparatus according to claim 1, further comprising a second intensity modulator and a third intensity modulator, wherein an input of the third intensity modulator is connected to an output of the second intensity modulator, the first phase modulator is disposed on the long arm, the second phase modulator is disposed on the short arm, or the first phase modulator is disposed on the short arm, and the second phase modulator is disposed on the long arm.
7. The high-speed quantum key encoding device of claim 1, wherein the encoding device further comprises a variable optical attenuator connected in series at an end of the encoding device, the variable optical attenuator being configured to reduce the overall signal strength to an optimal number of photons per pulse.
8. The high-speed quantum key encoding apparatus of claim 1, wherein the driving signal frequency of the light source, the first intensity modulator and the first phase modulator are the same, and the driving signal frequency of the second intensity modulator is twice the driving signal frequency of the light source.
9. The high-speed quantum key encoding device of claim 1, wherein the driving signal frequency of the light source, the first intensity modulator and the first phase modulator is 10MHz to 1GHz, and the driving signal frequency of the second intensity modulator is 20MHz to 2 GHz.
10. The high-speed quantum key encoding device of claim 4 or 6, wherein the driving signal frequency of the second phase modulator is 10 MHz-1 GHz, and the driving signal frequency of the second phase modulator is the same as the driving signal frequency of the light source.
11. The high-speed quantum key encoding device of claim 5 or 6, wherein the driving signal frequency of the third intensity modulator is 20 MHz-2 GHz, and the driving signal frequency of the third intensity modulator is twice the light source driving signal frequency.
12. The high-speed quantum key encoding device of any one of claims 1-11, wherein the light source is a periodic light pulse generating light source.
13. A high-speed quantum key coding method is applied to a high-speed quantum key coding device, and the method comprises the following steps:
generating a phase-random light pulse using a light source;
performing decoy state preparation, and attenuating the intensity of the optical pulse for preparing the decoy state by using a first intensity modulator;
performing phase encoding, changing one beam of light pulse generated by a light source into two beams of first sub-light pulses separated in time by using an unequal arm interferometer, and adjusting the phase difference of the two beams of first sub-light pulses by using a first phase modulator to enable the phase difference of the two beams of first sub-light pulses after being combined to be 0 or pi;
and performing time encoding and/or vacuum state preparation, and using a second intensity modulator to extinguish one of the two first sub-light pulses for time encoding and/or extinguish two of the two first sub-light pulses for vacuum state encoding.
14. The high-speed quantum key encoding method of claim 13, further comprising a re-extinction step of re-extinction using a third intensity modulator to re-extinguish the sub-optical pulses extinguished by the second intensity modulator.
15. The high-speed quantum key encoding method of claim 13, wherein the driving signal frequency of the light source, the first intensity modulator and the first phase modulator are the same, and the driving signal frequency of the second intensity modulator is twice the driving signal frequency of the light source.
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