Multi-user QKD system based on code division multiple access

Abstract

The utility model discloses a multi-user QKD (Quantum Key Distribution) system based on code division multiple access. The multi-user QKD system comprises a plurality of user sides, wherein one user side is a sender, and the other user sides are receivers; the sender comprises a laser source, a code division multiple access modulator and a QKD modulation module; the receiver comprises a QKD demodulation module and a code division multiple access demodulator. The utility model discloses a multi-user QKD (Quantum Key Distribution) system based on code division multiple access, which is characterized in that a pulse sequence is modulated by a code division multiple access modulator and a QKD modulation module in sequence, has related key information and multiple access information, is amplified by a coupler, and is transmitted to each receiver in multiple paths; according to the QKD communication method and the QKD communication system, key information is obtained after demodulation of the QKD demodulator and the code division multiple access demodulator in sequence, so that one-to-many multi-user QKD communication is realized, the QKD communication is performed by using the same frequency band in the same channel, the QKD communication method and the QKD communication system have the advantages of high spectrum utilization rate, large system capacity, strong anti-interference capability and the like, channel resource consumption is reduced, the system structure is simple, and expansibility is achieved.

Description

Technical Field

[0001] The utility model relates to the field of optical communication and quantum communication equipment, and in particular to a multi-user QKD system based on code division multiple access. Background Art

[0002] Quantum Key Distribution (QKD) is a research focus in the field of quantum communication. Based on the characteristics of quantum mechanics, quantum communication is theoretically absolutely secure. The communicating parties can maintain secure communication and obtain absolutely secure information even if there is an eavesdropper trying to eavesdrop. The eavesdropper cannot obtain the content of the communication.

[0003] The QKD protocol has evolved from the BB84 protocol first proposed in 1984 to the recent TF-QKD protocol. The TF-QKD protocol is based on the Measurement Device Independent (MDI)-QKD protocol that can resist attacks from the measurement end. The MDI-QKD protocol, which improves the defects of the measurement equipment, has also derived many important protocols. The current expansion of QKD to multi-user network communications is a key to the practical application of QKD quantum networks.

[0004] At present, WDM wavelength division multiplexing technology is mainly used to realize multi-user QKD network. WDM wavelength division multiplexing technology can effectively increase the number of channels that can be supported in a shared optical fiber channel, carry higher communication bandwidth, and improve wavelength utilization. With the continuous increase in the number of channels in the WDM transmission system, the nonlinear effect of single-mode optical fiber has intensified and has approached the nonlinear Shannon limit. With the increase in the number of users in the QKD network, WDM wavelength division multiplexing technology will occupy more and more channel resources for communication, and channel resources are scarce resources, which is difficult to meet the needs of QKD practical application.

[0005] Therefore, it is necessary to improve the existing QKD system and propose a QKD system that can effectively increase the number of users without occupying too many channel resources. Utility Model Content

[0006] In order to solve the problem that a multi-user QKD network currently implemented by using WDM wavelength division multiplexing technology occupies channels and consumes network resources, the utility model proposes a multi-user QKD system based on code division multiple access.

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

[0008] A multi-user QKD system based on code division multiple access includes multiple user terminals, one of which is a sender and the other user terminals are receivers.

[0009] The transmitter includes a laser source, a code division multiple access modulator and a QKD modulation module;

[0010] The receiver includes a QKD demodulation module and a code division multiple access demodulator;

[0011] The output end of the laser source is connected to an input end of the code division multiple access modulator, the output end of the code division multiple access modulator is connected to an input end of the QKD modulation module, the output end of the QKD modulation module is connected to the input end of the QKD demodulation module, and the output end of the QKD demodulation module is connected to an input end of the code division multiple access demodulator.

[0012] In the above scheme, the laser source of the transmitter generates a pulse sequence, which is modulated by the code division multiple access modulator and the QKD modulation module in turn, and then has relevant key information and multiple access information. It is then amplified by the coupler and multi-channel transmitted to each receiver. The key information is obtained after being demodulated by the QKD demodulator and the code division multiple access demodulator in turn, thereby realizing one-to-many multi-user QKD communication. By using the same frequency band in the same channel for QKD communication, it has the advantages of high spectrum utilization, large system capacity, strong anti-interference ability, etc. It will not occupy too many channel resources, and the system structure is simple and scalable.

[0013] Preferably, it also includes a coupler; the output end of the QKD modulation module is connected to the input end of each QKD demodulation module through the coupler.

[0014] Preferably, the transmitter further includes an attenuator; the output end of the laser source is connected to an input end of a code division multiple access modulator through the attenuator.

[0015] Preferably, the transmitter further includes a first control module; different output ends of the first control module are respectively connected to another input end of the code division multiple access modulator and another input end of the QKD modulation module.

[0016] Preferably, the first control module includes a first address code generator and a quantum random number generator;

[0017] Different output ends of the first address code generator are respectively connected to another input end of the code division multiple access modulator and an input end of the quantum random number generator, and the output end of the quantum random number generator is connected to another input end of the QKD modulation module.

[0018] Preferably, the receiver further includes a second control module; an output end of the second control module is connected to another input end of the code division multiple access demodulator.

[0019] Preferably, the second control module is a second address code generator; an output end of the second address code generator is connected to another input end of the code division multiple access demodulator.

[0020] Preferably, the laser source is a pulse laser generating device for generating a pulse sequence with phase randomness.

[0021] Preferably, the QKD modulation module is a phase modulator or a polarization modulator.

[0022] Beneficial technical effects of the utility model:

[0023] The utility model provides a multi-user QKD system based on code division multiple access, in which a pulse sequence is generated by a laser source of a transmitter, and after the pulse sequence is modulated by a code division multiple access modulator and a QKD modulation module in turn, the pulse sequence has relevant key information and multiple access information, and then is amplified by a coupler, and multi-channeled to each receiver, and after being demodulated by a QKD demodulator and a code division multiple access demodulator in turn, the key information is obtained, thereby realizing one-to-many multi-user QKD communication, and by using the same frequency band in the same channel for QKD communication, it has the advantages of high spectrum utilization, large system capacity, strong anti-interference ability, etc., does not occupy too many channel resources, and has a simple system structure and is extensible. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of module connection in one embodiment of the utility model;

[0025] Figure 2 This is a schematic diagram of module connection of another embodiment of the utility model;

[0026] Figure 3 Schematic diagram of the QKD process of the utility model;

[0027] Among them: 11, laser source; 12, code division multiple access modulator; 13, QKD modulation module; 14, attenuator; 15, first control module; 151, first address code generator; 152, quantum random number generator; 21, QKD demodulation module; 22, code division multiple access demodulator; 23, second control module; 30, coupler. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the utility model more clearly understood, the utility model is further described in detail below in conjunction with embodiments, but the scope of protection claimed in the utility model is not limited to the following specific embodiments.

[0029] Example 1

[0030] like Figure 1As shown, a multi-user QKD system based on code division multiple access includes multiple (n+1, n≥1) user terminals; one of the user terminals is a sender, and the other user terminals are receivers (such as receiver 1, receiver 2, receiver 3, ..., receiver n);

[0031] The transmitter includes a laser source 11, a code division multiple access modulator 12 and a QKD modulation module 13;

[0032] The receiver includes a QKD demodulation module 21 and a code division multiple access demodulator 22;

[0033] The output end of the laser source 11 is connected to an input end of the code division multiple access modulator 12, the output end of the code division multiple access modulator 12 is connected to an input end of the QKD modulation module 13, the output end of the QKD modulation module 13 is connected to the input end of the QKD demodulation module 21, and the output end of the QKD demodulation module 21 is connected to an input end of the code division multiple access demodulator 22.

[0034] In the specific implementation process, the laser source 11 of the transmitter generates a pulse sequence, which is then modulated by the code division multiple access modulator 12 and QKD modulated by the QKD modulation module 13, and then has relevant key information and multiple access information, and then transmitted to the coupler 30 through the quantum channel for amplification, and multi-channel transmission to each receiver; the encoded information of the pulse sequence is decoded by the QKD demodulator to obtain a key with code division multiple access information, and then demodulated by the code division multiple access demodulator 22 to obtain the user's unique key. The key information of each receiver after demodulation by the code division multiple access demodulator 22 is different according to its address code, thereby achieving the effect of code division multiple access. Therefore, one-to-many multi-user QKD communication is realized. By using the same frequency band in the same channel for QKD communication, it has the advantages of high spectrum utilization, large system capacity, strong anti-interference ability, etc., and the system structure is simple and extensible.

[0035] More specifically, a coupler 30 is also included; the output end of the QKD modulation module 13 is connected to the input end of each QKD demodulation module 21 through the coupler 30.

[0036] In a specific implementation process, the pulse sequence sent by the sender is broadcast to each receiver through the coupler 30.

[0037] More specifically, the transmitter further includes an attenuator 14 ; the output end of the laser source 11 is connected to an input end of the code division multiple access modulator 12 through the attenuator 14 .

[0038] In a specific implementation process, the average photon number of the pulse sequence is attenuated to below 1 by the attenuator 14 .

[0039] More specifically, the transmitter also includes a first control module 15; different output ends of the first control module 15 are respectively connected to another input end of the code division multiple access modulator 12 and another input end of the QKD modulation module 13.

[0040] In the specific implementation process, the code division multiple access modulator 12 and the QKD modulation module 13 are controlled by the first control module 15, and the pulse sequence is modulated according to the electrical signal provided by the first control module 15; wherein,

[0041] The code division multiple access modulator 12 performs intensity modulation on the pulse sequence according to the electrical signal provided by the first control module 15: when the electrical signal is 1, the corresponding pulse sequence intensity is not operated, and when the electrical signal is 0, the corresponding pulse sequence intensity is modulated to 0;

[0042] The QKD modulation module 13 encodes the pulse sequence according to the electrical signal provided by the first control module 15, and the encoding operation is specifically performed according to different QKD protocols.

[0043] After being modulated by the CDMA modulator 12 and the QKD modulation module 13, the pulse sequence already has CDMA information and QKD coding information.

[0044] Example 2

[0045] More specifically, Figure 2 As shown, the first control module 15 includes a first address code generator 151 and a quantum random number generator 152;

[0046] Different output ends of the first address code generator 151 are respectively connected to another input end of the code division multiple access modulator 12 and an input end of the quantum random number generator 152 , and the output end of the quantum random number generator 152 is connected to another input end of the QKD modulation module 13 .

[0047] In the specific implementation process, the first address code generator 151 of the sender combines the address code of the receiver to be communicated into a set of sequences according to mathematical operations, wherein the address code consists of 0 and 1, and then converts the sequence into an electrical signal to control the code division multiple access modulator 12. The quantum random number generator of the sender randomly generates a key sequence, performs a convolution operation on the key sequence and the address code sequence of the first address code generator 151, and converts it into an electrical signal to control the QKD modulation module 13, so as to realize the modulation of the pulses at the corresponding positions according to the different address codes (i.e., the different receivers), so as to achieve the purpose of code division multiple access.

[0048] More specifically, the receiving side further includes a second control module 23 ; an output end of the second control module 23 is connected to another input end of the CDMA demodulator 22 .

[0049] More specifically, the second control module 23 is a second address code generator; an output end of the second address code generator is connected to another input end of the CDMA demodulator 22 .

[0050] In a specific implementation process, the address code of each receiver is unique, and the second address code generator generates a dedicated address code of the receiver, thereby controlling the CDMA demodulator 22 to decode the sequence with CDMA information.

[0051] More specifically, the laser source 11 is a pulse laser generating device for generating a pulse sequence with phase randomness.

[0052] In the specific implementation process, the pulse sequence generated by the pulse laser generating device has phase randomness; the generated pulse sequence can be expressed as:

[0053]

[0054] Where k is the number of pulse trains and n is the average number of photons.

[0055] More specifically, the QKD modulation module 13 is a phase modulator or a polarization modulator.

[0056] In a specific implementation process, the pulse signal is phase-encoded by a phase modulator, or the pulse signal is polarization-encoded by a polarization modulator.

[0057] Example 3

[0058] like Figure 3 As shown, this embodiment provides a QKD process of a one-to-many multi-user QKD system based on code division multiple access, which is as follows:

[0059] S1: System initialization: Check the status of the multi-user network, check the user-side hardware facilities, check whether each device is operating normally, and set initial conditions and thresholds;

[0060] S2: The laser source 11 generates a pulse signal;

[0061] S3: decay the pulse signal to a single photon state;

[0062] S4: Code division multiple access modulation is performed on the pulse signal to make it have multi-user information;

[0063] S5: Perform QKD modulation on the pulse signal to make it have key information;

[0064] The pulse signal at this time carries the convolution information of multi-user information and key information;

[0065] S6: The QKD demodulator demodulates the signal pulse to obtain the convolution information of the multi-user information and the key information carried by the pulse signal;

[0066] S7: The CDMA demodulator 22 demodulates the convolution information to obtain an initial key;

[0067] S8: QBER comparison: compare the bit error rate QBER with the threshold value (preset according to the actual situation);

[0068] If it is greater than the threshold, then return to step S1; if it is not greater than the threshold: then execute step S9;

[0069] S9: Perform post-processing of quantum key distribution, process the initial key, and complete the quantum key distribution process.

[0070] According to the disclosure and teaching of the above specification, the technicians in the field of the utility model can also change and modify the above implementation. Therefore, the utility model is not limited to the specific implementation methods disclosed and described above, and some modifications and changes to the utility model should also fall within the scope of protection of the claims of the utility model. In addition, although some specific terms are used in this specification, these terms are only for convenience and do not constitute any limitation to the utility model.

Claims

1. A multi-user QKD system based on code division multiple access, characterized in that: It includes multiple user terminals; one of the user terminals is a sender, and the other user terminals are receivers; The transmitter includes a laser source, a code division multiple access modulator and a QKD modulation module; The receiver includes a QKD demodulation module and a code division multiple access demodulator; The output end of the laser source is connected to an input end of the code division multiple access modulator, the output end of the code division multiple access modulator is connected to an input end of the QKD modulation module, the output end of the QKD modulation module is connected to the input end of the QKD demodulation module, and the output end of the QKD demodulation module is connected to an input end of the code division multiple access demodulator.

2. A multi-user QKD system based on code division multiple access according to claim 1, characterized in that: It also includes a coupler; the output end of the QKD modulation module is connected to the input end of each QKD demodulation module through the coupler.

3. A multi-user QKD system based on code division multiple access according to claim 1, characterized in that: The transmitter also includes an attenuator; the output end of the laser source is connected to an input end of a code division multiple access modulator through the attenuator.

4. A multi-user QKD system based on code division multiple access according to claim 1, characterized in that: The transmitter also includes a first control module; different output ends of the first control module are respectively connected to another input end of the code division multiple access modulator and another input end of the QKD modulation module.

5. A multi-user QKD system based on code division multiple access according to claim 4, characterized in that: The first control module includes a first address code generator and a quantum random number generator; Different output ends of the first address code generator are respectively connected to another input end of the code division multiple access modulator and an input end of the quantum random number generator, and the output end of the quantum random number generator is connected to another input end of the QKD modulation module.

6. A multi-user QKD system based on code division multiple access according to claim 1, characterized in that: The receiver also includes a second control module; an output end of the second control module is connected to another input end of the code division multiple access demodulator.

7. A multi-user QKD system based on code division multiple access according to claim 6, characterized in that: The second control module is a second address code generator; the output end of the second address code generator is connected to the other input end of the code division multiple access demodulator.

8. A multi-user QKD system based on code division multiple access according to claim 1, characterized in that: The laser source is a pulse laser generating device, which is used to generate a pulse sequence with phase randomness.

9. A multi-user QKD system based on code division multiple access according to claim 1, characterized in that: The QKD modulation module is a phase modulator or a polarization modulator.

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