QKD intensity coding device and coding method capable of reducing code pattern effect

Abstract

The invention provides a QKD (quantum key distribution) intensity coding device and method capable of reducing a code pattern effect, and relates to the technical field of quantum communication. Generated random data streams are coded into data streams of tri-state optical pulses according to a coding rule of a pulse state; the three-state light pulse comprises a signal state light pulse, a vacuum state light pulse and a decoy state light pulse; based on a translation rule, translating the data stream of the three-state optical pulse into four kinds of coded modulation voltage digital signal sequences; converting the digital signal sequences of the four coded modulation voltages into four different modulation voltage signals; and modulating the intensity of the three-state optical pulse based on the four different modulation voltage signals.

Description

Technical Field

[0001] The present invention proposes a QKD intensity encoding device and encoding method capable of reducing the patterning effect, which relates to the technical field of quantum communication. Background Art

[0002] In existing QKD, weak coherent light is used as the light source. However, weak coherent light is not an ideal single-photon light source, and multi-photon pulses will cause additional security vulnerabilities and pose a security risk of photon number splitting attack. To make up for this vulnerability, in practical applications, the method of preparing decoy states is adopted to prepare decoy states with an average intensity weaker than that of the signal light. Currently, QKD protocols usually set three states with different intensities: signal state, decoy state, and vacuum state to ensure the security of communication.

[0003] Ideally, during the operation of QKD, for pulses of the same type, their intensities should be the same. However, in the practical application of QKD, since the modulation voltage of the intensity modulator is affected by the modulation voltage of the previous pulse, when the same modulation voltage is set for pulses of the same type, the intensities are different when the types of the previous pulses are different. This phenomenon is called the patterning effect. The security of QKD usually depends on the assumption that the transmitted pulses are independent and identically distributed; the patterning effect causes the intensity correlation of adjacent pulses and destroys the assumption of pulse intensity independence. An eavesdropper can obtain additional information to distinguish between the signal state and the decoy state, threatening the security of QKD.

[0004] To reduce the patterning effect, one way is to use a digital-to-analog converter (DAC) to perform pre-compensation on each modulation voltage signal based on the modulation voltage signal of the previous pulse. The optical pulses used in QKD are high-frequency signals, and high-speed DACs are required. However, high-speed DACs are very expensive, and usually only a limited number of voltage signals are generated and modulated in the system, making it impossible to perform complete signal pre-compensation. Another way is to reduce the patterning effect by changing the structure of the intensity modulation device, such as the solutions in patents CN114338004A and CN115333724A. However, changing the structure of the intensity modulation device means that the intensity modulation device has a special structure design, which is not compatible with existing commercial intensity modulators, affecting the practicality of QKD; moreover, the intensity ratio of the modulated signal state to the decoy state in such solutions is fixed and cannot be freely adjusted. Summary of the Invention

[0005] To solve the above technical problems, the present application proposes a QKD intensity encoding method capable of reducing the patterning effect, including:

[0006] Encoding the generated random data stream into a data stream of three-state light pulses according to the pulse state encoding rule; the three-state light pulses are a signal state light pulse, a vacuum state light pulse and a decoy state light pulse;

[0007] Based on a translation rule, the data stream of the tri-state optical pulse is translated into four coded modulation voltage digital signal sequences;

[0008] Converting the four coded modulation voltage digital signal sequences into four different modulation voltage signals;

[0009] The intensity of the tri-state light pulse is modulated based on the four different modulation voltage signals.

[0010] In a preferred embodiment, only one coded modulation voltage signal is set for the data streams of signal-state light pulses and vacuum-state light pulses. However, for the data streams of decoy-state light pulses, two coded modulation voltage signals are set according to the type of the previous light pulse. This ensures that after being affected by the previous light pulse, the output intensities of the data streams of light pulses of the same type after being modulated by the coded modulation voltage signal are close, thereby compensating for the modulation voltage signal of the decoy-state light pulse.

[0011] In a preferred embodiment, the data stream of tri-state light pulses is translated into a digital signal sequence of four coded modulation voltages according to the following translation rules:

[0012] The signal state pulse signal s is translated into a digital signal V of the signal state modulated voltage s ;

[0013] The vacuum state pulse signal v is translated into the vacuum state modulated voltage digital signal V v ;

[0014] If the previous pulse signal of the deceptive state pulse signal d is the signal state pulse signal s, the deceptive state pulse signal d is translated into the deceptive state first modulation voltage digital signal V d1 ;

[0015] If the previous pulse signal of the decoy pulse signal d is the decoy pulse signal d or the vacuum pulse signal v, the decoy pulse signal d is translated into the decoy second modulation voltage digital signal V d2 .

[0016] In a preferred embodiment, the data stream of the tri-state light pulse uses 2 bits to encode one light pulse state. Assume that the data stream of the tri-state light pulse before translation is:

[0017] ...a n b n a n+1 b n+1 a n+2 b n+2...

[0018] Among them, each group of n pulse signals a n b n are two bits for encoding an optical pulse state. Let 00 encode the vacuum state pulse signal v, 11 encode the signal state pulse signal s, and 01 and 10 encode the decoy state pulse signals d;

[0019] In the translated digital signal sequence of the modulation voltage, the type of the modulation voltage for encoding one optical pulse is encoded by two bits. Let the translated digital signal sequence of the modulation voltage be:

[0020] ...A n B n A n+1 B n+1 A n+2 B n+2 ...

[0021] Among them, each group of n digital signals A of the modulation voltage n B n are the digital signals of two bits of the modulation voltage for encoding one optical pulse after being translated by the pulse signals a n b n Let 00 encode the digital signal V of the modulation voltage of the vacuum state v , 11 encode the digital signal V of the modulation voltage of the signal state s , 01 encode the digital signal V of the first modulation voltage of the decoy state d1 , 10 encode the digital signal V of the second modulation voltage of the decoy state d2 ;

[0022] For all pulse signals, perform the following logical operations for translation:

[0023]

[0024] The present invention also proposes a QKD intensity encoding device capable of reducing the pattern effect for implementing the above QKD intensity encoding method. The QKD intensity encoding device includes: a data stream source, an FPGA, a digital-to-voltage conversion module, and an intensity modulator;

[0025] The data stream source includes one or more random number generators, and can output the generated random data stream encoded into a data stream of three-state optical pulses according to the encoding rules of the pulse state to the FPGA;

[0026] The FPGA translates the data stream of the three-state optical pulses into a digital signal sequence of four encoded modulation voltages based on the compilation rules;

[0027] The digital-to-voltage conversion module converts the digital signal sequence of the four encoded modulation voltages into four different modulation voltage signals and loads them onto the intensity modulator;

[0028] The intensity modulator modulates the intensity of the three-state optical pulse based on the four different modulation voltage signals.

[0029] Compared with the prior art, the present invention has the following beneficial technical effects:

[0030] The intensity encoding device and encoding method of QKD of the present invention translate the data stream of the three-state optical pulse into a digital signal sequence of four encoded modulation voltages, and convert them into four modulation voltages, and modulate the intensity of the three-state optical pulse based on the four different modulation voltage signals. The present invention can reduce the influence of the code pattern effect without adding additional electrical signal channels. In the QKD transmitter of the present application, a random number generator, an FPGA, and a digital-to-voltage conversion module are provided, which can improve the security of QKD while not increasing the device complexity additionally. Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative efforts.

[0032] Figure 1 Schematic diagram of the device settings of the QKD intensity encoding device of the present invention;

[0033] Figure 2 Flowchart of the QKD intensity encoding method of the present invention;

[0034] Figure 3 Schematic diagram of the intensity of the decoy state pulse signal when the previous pulse is a signal state pulse signal;

[0035] Figure 4 Schematic diagram of the intensity of the decoy state pulse signal when the previous pulse is a decoy state pulse signal;

[0036] Figure 5 Schematic diagram of the intensity of the decoy state pulse signal when the previous pulse is a vacuum state pulse signal. Detailed Embodiments

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts belong to the scope of protection of this application.

[0038] In the accompanying drawings of the specific embodiments of the present invention, in order to better and more clearly describe the working principles of the components in the system and show the connection relationships of the various parts in the device, only the relative positional relationships between the components are clearly distinguished, and it does not constitute a limitation on the signal transmission direction, connection sequence, and the sizes, shapes of the various parts of the structure within the component or structure.

[0039] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation manner of the present invention. The "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is separate or selectively mutually exclusive with other embodiments.

[0040] Embodiment 1

[0041] Device Settings of the QKD Intensity Encoding Device

[0042] The device settings of the QKD intensity encoding device in this application are as Figure 1 shown, including a data stream source, an FPGA (Field Programmable Gate Array), a digital-to-voltage conversion module, and an intensity modulator.

[0043] The data stream source may include one or more random number generators, which can encode the generated random data stream into a data stream of three-state optical pulses (signal state, vacuum state, and decoy state) according to the pulse-state encoding rule and output it to the FPGA as information such as quantum state intensity encoding.

[0044] It should be explained that: the rule refers to the rule for setting the type of encoding pulse according to the data stream.

[0045] It should be noted that the data stream refers to the data sequence used to encode optical pulses, which is a random bit sequence generated by a random number generator in actual applications.

[0046] The FPGA can translate the data stream of three-state optical pulses (signal state, vacuum state, and decoy state) into a digital signal sequence of four encoded modulation voltages based on the set translation rule, and modulate the quantum state with different encoded digital signals of modulation voltages without changing the quantum state encoded data.

[0047] The digital - voltage conversion module can convert the digital signal sequence of the modulated voltage with four encodings into four different modulated voltage signals, which are loaded onto the intensity modulator;

[0048] It should be explained that: the intensity modulator cannot change the voltage through the digital signal. It needs to be converted into the corresponding voltage signal through the digital - voltage conversion module to control the modulated voltage loaded on the intensity modulator.

[0049] The intensity modulator can modulate the intensity of the three - state optical pulse based on the modulated voltage signal.

[0050] Embodiment 2

[0051] Intensity encoding method

[0052] The flow chart of the intensity encoding method of this application is as Figure 2 shown. The generated random data stream is encoded into the data stream of the three - state optical pulse according to the encoding rules of the pulse state; the three - state optical pulse is the signal - state optical pulse, the vacuum - state optical pulse, and the decoy - state optical pulse; based on the translation rule, the data stream of the three - state optical pulse is translated into the digital signal sequence of the modulated voltage with four encodings, which is converted into four different modulated voltage signals by the digital - voltage conversion module. Among them, the data streams of the signal - state optical pulse and the vacuum - state optical pulse are both set with one kind of encoded modulated voltage signal, while the data stream of the decoy - state optical pulse is set with two kinds of encoded modulated voltage signals according to the type (signal - state, decoy - state, and vacuum - state) of the previous optical pulse, so that after being affected by the previous pulse, the output intensities of the data streams of the optical pulses of the same type after being modulated by the encoded modulated voltage signals are close, realizing the compensation for the modulated voltage signal of the decoy - state optical pulse.

[0053] It should be explained that: if only one kind of modulated voltage signal is used to modulate the decoy - state, then due to the pattern effect, the intensity of the decoy - state will have obvious differences. The encoding method of this embodiment uses two kinds of modulated voltage signals to modulate the decoy - state, making the intensities of the optical pulses with the same state (signal - state, decoy - state, and vacuum - state) close.

[0054] The following experiments were carried out on the technical solution of the present invention: when the same modulated voltage signal is set for the optical pulses of each state, the type of the previous - state optical pulse has little influence on the output pulse - signal intensity of the signal - state and the vacuum - state. For the decoy - state, when the type of the previous - state optical pulse is the decoy - state and the vacuum - state, the difference in the output pulse - signal intensity is not significant; however, when the type of the previous - state optical pulse is the signal - state, compared with the above two cases, the output intensity has obvious differences. The actual test results are as Figure 3 、 Figure 4 、 Figure 5 shown, where the horizontal dotted line represents the average output intensity of the decoy - state pulse signal.

[0055] As can be seen from the figure, when the previous optical pulse signal is in the signal state and the subsequent optical pulse signal is in the decoy state, the intensity of the output pulse signal is significantly lower than the case when the previous optical pulse signal is in the decoy state or the vacuum state.

[0056] In the present invention, the FPGA translates the data stream of the three-state optical pulse into a digital signal sequence of four kinds of encoded modulation voltages according to the following translation rules.

[0057] The specific translation rules are as follows:

[0058] The signal-state pulse signal s is translated into the digital signal V of the signal-state modulation voltage s ;

[0059] The vacuum-state pulse signal v is translated into the digital signal V of the vacuum-state modulation voltage v ;

[0060] If the previous pulse signal of the decoy-state pulse signal d is the signal-state pulse signal s, then the decoy-state pulse signal d is translated into the digital signal V of the first decoy-state modulation voltage d1 ;

[0061] If the previous pulse signal of the decoy-state pulse signal d is the decoy-state pulse signal d or the vacuum-state pulse signal v, then the decoy-state pulse signal d is translated into the digital signal V of the second decoy-state modulation voltage d2 .

[0062] For example, before translation, the data stream of the three-state optical pulse is:

[0063] s,d,d,v,s,d,d,v,d,v,s,d,v,...

[0064] Then the digital signal sequence of the encoded modulation voltage after translation is:

[0065] V s ,V d1 ,V d2 ,V v ,V s ,V d1 ,V d2 ,V v ,V d2 ,V v ,V s ,V d1 ,V v ,...

[0066] The digital-voltage conversion module sets the corresponding modulation voltage signal for the digital signal of each modulation voltage, and the digital signal of the first decoy-state modulation voltage and the digital signal of the second decoy-state modulation voltage are adjusted with reference to the optical intensity monitoring in the actual system.

[0067] Example 3

[0068] The following gives an example of the logical operation of converting a three-state pulse signal into a digital signal of four modulation voltages.

[0069] In the example, the data stream source encodes the state of 1 pulse with 2 bits in the three-state data stream, that is, every 2 adjacent bits in the random bit sequence generated by the random number generator form a group, and a group of encodings corresponds to the state of 1 pulse. These 2 bits can come from the same random number generator or from different random number generators respectively.

[0070] In a group of 2 bits encoding 1 pulse, let 00 encode the vacuum state pulse signal v, 11 encode the signal state pulse signal s, and 01 and 10 encode the decoy state pulse signal d.

[0071] The translated digital signal sequence of the modulation voltage encodes the modulation voltage of 1 pulse with 2 bits. In a group of 2 bits encoding 1 pulse (in the translated digital signal sequence, a group of bits encoding the state is translated into a group of 2-bit digital signals encoding the modulated voltage, and each group of bits encodes the digital signal of the modulated voltage of 1 pulse), let 00 encode the digital signal V of the vacuum state modulation voltage v , 11 encodes the digital signal V of the signal state modulation voltage s , 01 encodes the digital signal V of the first modulation voltage of the decoy state d1 , 10 encodes the digital signal V of the second modulation voltage of the decoy state d2 .

[0072] Suppose the data stream of the three-state optical pulse before translation is:

[0073] ...a n b n a n+1 b n+1 a n+2 b n+2 ...

[0074] where each group of n pulse signals (a n b n ) is 2 bits encoding the state of 1 pulse.

[0075] Suppose the translated digital signal sequence of the encoded modulation voltage is:

[0076] ...A n B n A n+1 B n+1 A n+2 B n+2 ...

[0077] Among them, the digital signal (A n B n ) of each group of modulation voltages is the encoding of 2 bits that translate the pulse signal (a n b n ) into a pulse-modulated voltage.

[0078] The FPGA performs the following logical operations for translation, for all pulse signals:

[0079]

[0080] Under this logical operation, the signal-state pulse signal 11 can be translated into the digital signal 11 of the signal-state modulation voltage; the vacuum-state pulse signal 00 can be translated into the digital signal 00 of the vacuum-state modulation voltage; if the previous pulse signal of the decoy-state pulse signal 01 / 10 is 11, it is translated into the digital signal 01 of the first modulation voltage of the decoy state; if the previous pulse signal of the decoy-state pulse signal 01 / 10 is 00 / 01 / 10, it is translated into the digital signal 10 of the second modulation voltage of the decoy state.

[0081] Those skilled in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, database, or other medium used in the embodiments provided in this application can include at least one of non-volatile and volatile memories. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc. The databases involved in the embodiments provided in this application can include at least one of relational databases and non-relational databases. Non-relational databases can include distributed databases based on blockchain, etc., and are not limited thereto. The processors involved in the embodiments provided in this application can be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, data processing logics based on quantum computing, etc., and are not limited thereto.

[0082] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0083] The above-described embodiments only represent several implementation manners of this application. The description is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of this application. It should be noted that for those of ordinary skill in the art, without departing from the concept of this application, several modifications and improvements can still be made, and these all belong to the protection scope of this application. Therefore, the protection scope of this application should be subject to the appended claims.

Claims

1. A QKD intensity encoding method capable of reducing the pattern effect, characterized in that Including: Encoding the generated random data stream into a data stream of tri-state optical pulses according to the encoding rule of pulse states; The tri-state optical pulses are signal-state optical pulses, vacuum-state optical pulses, and decoy-state optical pulses; Based on the translation rule, translating the data stream of the tri-state optical pulses into a digital signal sequence of four-encoded modulation voltages; Converting the digital signal sequence of the four-encoded modulation voltages into four different modulation voltage signals; Modulating the intensity of the tri-state optical pulses based on the four different modulation voltage signals.

2. The QKD intensity encoding method capable of reducing the pattern effect according to claim 1, wherein For the data streams of the signal-state optical pulses and the vacuum-state optical pulses, only one-encoded modulation voltage signal is set. For the data stream of the decoy-state optical pulses, two-encoded modulation voltage signals need to be set according to the type of the previous optical pulse, so that after being affected by the previous optical pulse, the output intensities of the data streams of the optical pulses of the same type after being modulated by the encoded modulation voltage signals are close, realizing the compensation of the modulation voltage signals of the decoy-state optical pulses.

3. The QKD intensity encoding method capable of reducing the pattern effect according to claim 2, wherein Translate the data stream of the tri-state optical pulses into a digital signal sequence of four-encoded modulation voltages according to the following translation rule: The signal-state pulse signal s is translated into a digital signal V of the signal-state modulation voltage s ; The vacuum state pulse signal v is translated into the digital signal V of the vacuum state modulation voltage v ; If the previous pulse signal of the decoy state pulse signal d is the signal state pulse signal s, then the decoy state pulse signal d is translated into the digital signal V of the decoy state first modulation voltage d1 ; If the previous pulse signal of the decoy state pulse signal d is the decoy state pulse signal d or the vacuum state pulse signal v, the decoy state pulse signal d is translated into the digital signal V of the second modulation voltage of the decoy state d2 .

4. The QKD intensity encoding method capable of reducing the pattern effect according to claim 3, wherein In the data stream of the tri-state optical pulses, 1 optical pulse state is encoded by 2 bits. Let the data stream of the tri-state optical pulses before translation be: ...a n b n a n+1 b n+1 a n+2 b n+2 ... Among them, each group of n pulse signals a n b n are two bits for encoding an optical pulse state. Let 00 encode the vacuum state pulse signal v, 11 encode the signal state pulse signal s, and 01 and 10 encode the decoy state pulse signal d; In the translated digital signal sequence of the modulation voltage, the type of the modulation voltage of 1 optical pulse is encoded by 2 bits. Let the translated digital signal sequence of the modulation voltage be: ...A n B n A n+1 B n+1 A n+2 B n+2 ... Among them, the digital signal A of the modulation voltage for each group of n n B n is the digital signal of two bits encoding the modulation voltage of an optical pulse after the pulse signals a n b n Let the digital signal of the modulation voltage encoding a vacuum state be V with 00 v , and the digital signal of the modulation voltage encoding a signal state be V with 11 s , the digital signal of the modulation voltage encoding the first decoy state be V with 01 d1 , and the digital signal of the modulation voltage encoding the second decoy state be V with 10 d2 ; For all pulse signals, perform the following logical operations for translation:

5. A QKD intensity encoding device capable of reducing the pattern effect, characterized in that, For implementing the QKD intensity encoding method described in any one of claims 1-4, the QKD intensity encoding device includes: a data stream source, an FPGA, a digital-to-voltage conversion module, and an intensity modulator; The data stream source includes one or more random number generators, and can encode the generated random data stream into a data stream of tri-state optical pulses and output it to the FPGA according to the encoding rule of pulse states; The FPGA, based on the compilation rule, translates the data stream of the tri-state optical pulses into a digital signal sequence of four-encoded modulation voltages; The digital-to-voltage conversion module converts the digital signal sequence of the four-encoded modulation voltages into four different modulation voltage signals and loads them onto the intensity modulator; The intensity modulator modulates the intensity of the tri-state optical pulses based on the four different modulation voltage signals.

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