A continuous variable quantum key distribution uplink networking device and system

Abstract

This invention discloses an uplink networking device and system for continuous-variable quantum key distribution, belonging to the field of quantum key distribution. The core of the device is a 2×2 lossless beam combining unit. N lossless beam combining units are combined together in a "cascaded" or "binary tree" manner to form a beam combining system, ultimately combining multiple coherent beams into one, achieving lossless beam combining. In the system, each transmitting end prepares optical signals using a local oscillator or an accompanying local oscillator scheme and transmits them to the uplink networking device via time-division multiplexing. Through N-to-1 "cascaded" or "binary tree" lossless beam combining structure, the optical signals are combined into one path and transmitted to the receiving end. Then, the receiving end generates or acquires the corresponding local oscillator light to receive and coherently detect the continuous-variable quantum optical signal. Finally, the coherent detection results are post-processed to obtain the key information. This invention can achieve lossless beam combining, minimizing channel loss and improving the system's signal-to-noise ratio.

Description

Technical Field

[0001] This invention belongs to the field of continuous variable quantum key distribution, specifically a continuous variable quantum key distribution uplink networking device and system. Background Technology

[0002] The strong compatibility of continuous-variable quantum key distribution with existing telecommunications infrastructure enables it to operate under high noise levels and provides a high key generation rate. Its advantages include low cost, high reliability, and high security code rate over metropolitan or access network distances. It can also make full use of mature commercial fiber optic communication devices.

[0003] The uplink access network for continuous-variable quantum key distribution enables long-distance, high-quality quantum key distribution, expanding the coverage of quantum key distribution networks. Furthermore, the uplink access network enhances system flexibility and scalability, making quantum key distribution technology easier to apply to various communication scenarios, including enterprise communications, inter-agency communications, and financial transactions.

[0004] In summary, continuous variable quantum key distribution uplink access networks are an important technological foundation for achieving secure and efficient communication, and help to build more secure and reliable communication networks.

[0005] However, the core problem faced by continuous-variable quantum key distribution uplink access networks is severe channel loss:

[0006] During fiber optic transmission, the extremely weak quantum signal will gradually weaken due to fiber loss and attenuation, resulting in limited transmission distance and affecting the rate and reliability of key distribution.

[0007] In uplink access networks, the current mainstream solution connects multiple user transmitters deployed at terminals to a receiver deployed at a single node via a passive optical combiner, with a transmittance of T = 1 / N. N is the number of users. Physically, the more users there are, the lower the transmittance and the higher the channel loss. Doubling the number of users adds 3dB to the channel loss. For a 32-user network, the loss from the beam splitter alone reaches 15dB, severely limiting system performance.

[0008] In summary, for continuous variable quantum key distribution uplink access networks, it is urgent to solve the key technical problem of beam combining loss suppression, realize an extremely low-loss optical quantum signal beam combining device, design a low-loss, high-speed continuous variable quantum key distribution uplink networking system, and provide a corresponding networking method for it. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides an uplink networking device and system for continuous variable quantum key distribution. The beam combining structure employs an extremely low-loss optical quantum signal beam combining device, based on an N-to-1 topology network structure, and uses a time-division multiplexing networking scheme. Theoretically, lossless beam combining can be achieved, minimizing channel loss and improving the system's signal-to-noise ratio.

[0010] The continuous variable quantum key distribution uplink networking device has a core of 2×2 lossless beam combining units. By cascading or forming a binary tree, N lossless beam combining units are combined together to form a beam combining system, which ultimately combines multiple coherent beams into one beam, achieving lossless beam combining.

[0011] The 2×2 lossless beam combining unit includes two input ports for receiving quantum signals from two different user transmitters; the first output port outputs the combined quantum signal, and the second output port outputs a signal of 0.

[0012] The lossless beam combining unit includes a phase shifter Φ, a phase shifter θ, and two 50:50 2×2 beam splitters. The quantum signal from the user's transmitter is loaded onto the optical carrier via a modulator to form an optical signal. When the lossless beam combining unit consists of 50:50 beam splitters, once the first phase shifter Φ fixes the relative phase of the two input beams according to the real-time phase compensation module, adjusting the second phase shifter θ will not affect the relative phase change of the two input beams at the output. This allows the structure to perform coherent beam combining without requiring specific intensity and phase relationships of the input light; as long as the light is coherent with the same polarization, lossless beam combining can be achieved by adjusting the two phase shifters.

[0013] By controlling the phase shifters Φ and θ to control the relative phase of the two input optical signals, the final effect is that, for any two input signals, by adjusting the phase shifters Φ and θ, one of the two outputs is the combined signal and the other is 0.

[0014] The process by which this device achieves lossless beam combining is as follows:

[0015] A coherent beam of arbitrary amplitude and phase is input into the beam combiner structure from two input ports. The first phase shifter Φ is adjusted so that the output beam of this path is out of phase with the other normal input beam. After the two inverted beams pass through a 50:50 2×2 beam splitter, the amplitude of the beam at the output end is adjusted by the second phase shifter θ. After the beam and the other normal beam pass through the 50:50 2×2 beam splitter, the output power of the second output port is reduced to 0. This is equivalent to combining the input beams and outputting them all from the first output port, thus achieving coherent beam combining of the two input beams.

[0016] The entire transmission process is represented by the following matrix:

[0017]

[0018] Among them, E O1 and E O2 E represents the signal power of the first output port and the second output port, respectively. I1 and E I2 Let r represent the signal power of the first input port and the second input port, respectively; r be the transmission efficiency of the straight-through port; and t be the transmission efficiency of the cross-connect port. For a 50:50 2×2 beam splitter

[0019] For two users, when two coherent beams of light with the same amplitude are input simultaneously, due to the orthogonality of light transmission, the initial amplitudes of the light at the two output ports are the same. By adjusting the phase shifter Φ = 0, the relative phase of the two input beams at the output ports is changed. By adjusting the phase shifter θ, the splitting ratio of the two input beams at the output ports is changed. When θ = π / 2, the splitting ratios of the two input beams at the output ports are the same. This is equivalent to combining the input light signals and outputting them all from the first output port, reducing the output power of the second output port to 0, i.e., E. O2 =0, thus achieving coherent beam combining of the two input optical signals.

[0020] For two users, when two coherent beams of light with different amplitudes are input simultaneously, the phase shifter Φ is controlled so that the phase difference between the two beams at one of the output ports is π, i.e. they are in opposite directions, while the phase difference at the other end is 0, i.e. they are in the same direction. Then, by adjusting the phase shifter θ, the amplitudes at the opposite ends are made the same, and the two beams will coherently cancel each other out, while the beams at the same phase ends will coherently construct each other, thus combining the beams.

[0021] The continuous variable quantum key distribution uplink networking system:

[0022] First, each continuous variable quantum key distribution transmitter prepares optical signals using a local oscillator or a local oscillator scheme, and then sends the prepared optical signals to the uplink networking device through time-division multiplexing. The optical signals are then combined into one path through N-to-1 cascading or a binary tree lossless beam combining structure and sent to the receiving end.

[0023] For time-division multiplexing continuous-variable quantum key distribution uplink networking, at a certain moment there is only one user input, and the phase shift of phase shifter Φ is 0. By adjusting phase shifter θ, the splitting ratio of the two input beams at the output port is changed. When the phase shift of phase shifter θ is π, it is equivalent to combining the input light signals and outputting them all from the second output port. The output power of the first output port is reduced to 0, i.e., E O1=0, thereby achieving lossless output of the input optical signal, enabling this user to perform lossless beam combining with users at other times.

[0024] Then, the receiving end generates or acquires the corresponding local oscillator light, receives the optical signal and performs coherent detection; finally, the coherent detection results are post-processed to obtain key information.

[0025] In the time-division multiplexing scheme, the transmitters of N user terminals transmit quantum signals to the node receivers in different time slots through optical delay modules, and the receivers receive and process them in chronological order.

[0026] The receiving end obtains two canonical components each of the quantum signal and the reference signal through time-decomposition multiplexing and coherent detection. Based on this, it performs data processing and post-processing steps such as phase recovery. After the modulated quantum state information is transmitted over a long distance through the quantum channel, the received signal will be superimposed with noise, and the channel loss will reduce the signal amplitude. If eavesdropping occurs, the information under test will be leaked, thus detecting the eavesdropping. This will result in the received information being different from the original modulated data, although there is a correlation between the two. Data post-processing needs to recover the quantum information from the noise, remove the influence of eavesdropping on the information, and extract the security key using the correlation between the two sets of data. Data post-processing consists of four steps: measurement basis selection, quantum channel parameter estimation, information negotiation, and privacy amplification of the security key, ultimately achieving the extraction of the security key.

[0027] The beneficial effects of this invention are as follows:

[0028] (1) The continuous variable quantum key distribution uplink networking device and system adopts an N-in-1 topology, which can minimize channel loss, effectively reduce the attenuation of the signal during transmission, and improve the efficiency and quality of channel transmission.

[0029] (2) Continuous variable quantum key distribution uplink networking device and system; by reducing channel loss, the signal-to-noise ratio of the system is improved, the noise and interference that may be introduced during transmission are reduced, the anti-interference ability and stability of the system are enhanced, and the generation efficiency and security of quantum keys are improved.

[0030] (3) Continuous variable quantum key distribution uplink networking device and system; by reducing channel loss and improving signal-to-noise ratio, the overall network performance is improved, including higher transmission efficiency, stronger anti-interference ability and more stable system operation, providing strong support for the development of quantum key distribution technology.

[0031] (4) Continuous variable quantum key distribution uplink networking device and system; adopting an N-in-1 networking topology, the quantum state combination transmission is carried out through time division multiplexing, which improves the transmission efficiency and capacity of the system, meets the needs of large-scale quantum communication, and is conducive to promoting the application and development of quantum communication technology.

[0032] (5) Continuous variable quantum key distribution uplink networking device and system; the provided networking structure has strong scalability and can flexibly meet the needs of communication networks of different scales and complexities, laying a solid foundation for building large-scale quantum communication networks and facilitating the commercialization and popularization of quantum communication technology.

[0033] (6) Continuous variable quantum key distribution uplink networking device and system; by minimizing channel loss, the operating cost and energy consumption of the communication system are reduced, the overall efficiency and economy of the system are improved, and it helps to promote the application and popularization of quantum communication technology in a wider range of fields. Attached Figure Description

[0034] Figure 1 This is a structural diagram of the 2×2 lossless beam combining unit in the continuous variable quantum key distribution uplink networking device of the present invention;

[0035] Figure 2 This is the cascaded networking structure in the continuous variable quantum key distribution uplink networking device of the present invention;

[0036] Figure 3 This is the binary tree networking structure in the continuous variable quantum key distribution uplink networking device of the present invention;

[0037] Figure 4 This is a schematic diagram of an uplink network for continuous variable quantum key distribution according to the present invention;

[0038] Figure 5 This is a schematic diagram of a time-division multiplexing scheme for a continuous variable quantum key distribution uplink networking system according to the present invention; Detailed Implementation

[0039] To facilitate understanding and implementation of the present invention by those skilled in the art, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some, not all, embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the scope of protection of the present invention.

[0040] This invention provides an uplink networking device and system for continuous variable quantum key distribution. The networking strategy integrates multiple key steps in quantum key distribution, taking into account factors such as security, efficiency, and flexibility, making the system more practical and widely applicable.

[0041] The core of the continuous variable quantum key distribution uplink networking device is a 2×2 lossless beam combining unit, such as... Figure 1 As shown, the 2×2 lossless beam combining unit includes two input ports, which are used to receive quantum signals from two different user transmitters; the first output port outputs the combined quantum signal, and the second output port outputs a signal of 0.

[0042] The lossless beam combining unit includes a phase shifter Φ, a phase shifter θ, and two 50:50 2×2 beam splitters. The quantum signal from the user transmitter is loaded onto the optical carrier through a modulator to form an optical signal. The phase shifter Φ is used to control the relative phase of the two input optical signals. The phase shifter θ is responsible for adjusting the amplitude of the two optical signals at the output.

[0043] The process by which this device achieves lossless beam combining is as follows:

[0044] A coherent light beam with arbitrary amplitude and phase is input from two input ports. By adjusting the first phase shifter Φ, the output light of this path is out of phase with the other normally input light signal. After the two inverted light signals pass through a 50:50 2×2 beam splitter, the amplitude of the light at the output end is adjusted by adjusting the second phase shifter θ. After the light signal and the other normally input light signal pass through the 50:50 2×2 beam splitter, the output power of the second output port is reduced to 0. This is equivalent to combining the input light signals and outputting them all from the first output port, thus achieving coherent beam combining of the two input light signals.

[0045] The entire transmission process is represented by the following matrix:

[0046]

[0047] Among them, E O1 and E O2 E represents the signal power of the first output port and the second output port, respectively. I1 and E I2 Let r represent the signal power of the first input port and the second input port, respectively; r be the transmission efficiency of the straight-through port; and t be the transmission efficiency of the cross-connect port. For a 50:50 2×2 beam splitter

[0048] Combining formulas (1) and (2), the relationship between the output signal and the input signal after passing through the 2×2 lossless bundle combiner unit is obtained as follows:

[0049] E O1 =(r 2 e iθ +t 2 )e iΦ E I1 +(tr+tre iθ E I2 (3)

[0050] E O2 =(tre iθ +tr)e iΦ E I1 +(r 2 +t 2 e iθ E I2 (4)

[0051] When two coherent beams of light with the same amplitude are input simultaneously, due to the orthogonality of light transmission, the initial amplitudes of the light at the two output ports are the same. By adjusting the phase shifter θ, the splitting ratio of the two input beams at the output ports is changed. At this point, the two input beams have the same splitting ratio at the output port. By adjusting the phase shifter Φ, the relative phase of the two input beams at the output port is changed. Assume E I1 =E I2 =1, when Φ=0, according to the input-output formula of the lossless combiner, E can be obtained. O1 =2,E O2 =0. This achieves the effect of lossless bundle combining.

[0052] When two coherent beams of light with different amplitudes are input simultaneously, the phase shifter Φ is controlled so that the phase difference between the two beams at one of the output ports is π, i.e. they are in opposite directions, while the phase difference at the other end is 0, i.e. they are in the same direction. Then, by adjusting the phase shifter θ, the amplitudes at the opposite ends are made the same, and the two beams will coherently cancel each other out, while the beams at the same phase ends will coherently construct each other, thus combining the beams.

[0053] Based on the coherent beam combining principle of the Mach-Zehnder interferometer, multiple lossless beam combining units are combined together to form a beam combining system, which can combine multiple coherent beams into one beam.

[0054] Based on this lossless beam combining unit, N lossless beam combining units can be combined together in a "cascaded" or "binary tree" arrangement to form a beam combining system, ultimately combining multiple coherent beams into one beam, realizing an uplink networking device for continuous variable quantum key distribution with extremely low beam combining loss of N-to-1.

[0055] like Figure 2As shown, for a cascaded network structure, input light 1 and input light 2 first need to be combined into one beam through a lossless beam combining unit, and then combined into one beam with other input light through another lossless beam combining unit. Finally, all input light is combined into one beam through cascading. The cascaded network structure has a high degree of freedom, but it requires processing the optical signal step by step, so the beam combining rate is relatively slow. This scheme is suitable for scenarios with a small number of users.

[0056] like Figure 3 As shown, the binary tree network structure allows two incident light beams to be combined into one beam through a lossless beam combining unit. Each combined beam is then paired with another lossless beam combining unit to be combined into one beam, and finally all optical signals are combined together. The binary tree network can combine two beams of light together when processing optical signals, so the time required is greatly improved compared with the cascaded structure. However, the number of incident light beams is often required to be an integer multiple of 2. This solution is suitable for scenarios with a large number of users and has better scalability and stability.

[0057] This modular design can flexibly adapt to the needs of networks of different sizes. By increasing or decreasing the number of basic units and adjusting the bundle structure, the system can be made to work efficiently with different numbers of users.

[0058] like Figure 4 As shown, the specific process of the continuous variable quantum key distribution uplink networking system is as follows:

[0059] Step 1: The transmitting end of each continuous variable quantum key distribution uses a local oscillator or in-path local oscillator scheme to prepare optical signals;

[0060] The specific process of preparing signal light using a local oscillator is as follows:

[0061] First, the transmitting end uses a laser and a modulator to generate pulsed or continuous wave signals;

[0062] Then, the pulsed or continuous wave signal is modulated into quantum signal light, allowing the quantum signal to carry encoded information. To reduce crosstalk between the reference light and the quantum signal light, the phase reference light is modulated at a different frequency.

[0063] Finally, the modulated quantum signal light and the phase reference light are coupled and attenuated to a level that meets the safety and system performance requirements by an attenuator to obtain the signal light;

[0064] The specific process of preparing signal light using a local oscillator along the path is as follows:

[0065] First, the transmitting end generates pulsed or continuous wave signals using a laser;

[0066] Subsequently, the beam splitter splits the pulse signal into quantum signal light and local oscillator light. The quantum signal light is modulated by a modulation module that includes intensity and phase modulation to modulate the quantum state, and the encoded information is loaded into the quantum signal light. A continuous variable quantum signal is then prepared by an attenuator.

[0067] Finally, the attenuated quantum signal light is coupled with the local oscillator light using a polarization beam combiner to obtain the signal light.

[0068] Step 2: Each transmitting end sends its prepared optical signal to the uplink networking device via time-division multiplexing networking. The optical signal is then combined into one path and sent to the receiving end through N-to-1 cascading or a binary tree lossless beam combining structure.

[0069] For different application scenarios and needs, the uplink networking system for continuous variable quantum key distribution can adopt a time-division multiplexing signal multiplexing scheme.

[0070] like Figure 5 As shown, in the time-division multiplexing scheme, the transmitters of N user terminals transmit quantum signals to the node receiver sequentially in different time slots through optical delay modules. Each user terminal sends quantum signals in different time periods, and the receiver receives and processes them in chronological order. This method ensures the integrity and strength of each signal by dividing the signal transmission time in the time domain, allowing each user terminal to send a signal in its dedicated time slice.

[0071] For time-division multiplexing continuous-variable quantum key distribution uplink networking, at a certain moment there is only one user input, and the phase shift of phase shifter Φ is 0. By adjusting phase shifter θ, the splitting ratio of the two input beams at the output port is changed. When the phase shift of phase shifter θ is π, it is equivalent to combining the input light signals and outputting them all from the second output port. The output power of the first output port is reduced to 0, i.e., E O1 =0, thereby achieving lossless output of the input optical signal, enabling this user to perform lossless beam combining with users at other times.

[0072] If time-division multiplexing is used for transmission, although the data of each user is still converted into optical signals through Gaussian modulation or other modulation methods, each signal is transmitted independently and sampled at the receiving end within the corresponding time period. Therefore, cross-modulation will not affect other users. The optical communication system can effectively handle multiple concurrent signals and does not require a complex synchronization mechanism.

[0073] Step 3: The receiving end generates or acquires the corresponding local oscillator light, separates the signals of each user through time demultiplexing, and performs reception and coherent detection.

[0074] Depending on the local oscillator (LO) optical scheme, the process by which the receiver acquires the LO differs; specifically:

[0075] When the transmitting end generates signal light using a local oscillator, the receiving end uses a local laser, or a laser in conjunction with a modulator, to generate the corresponding local oscillator light.

[0076] When the transmitting end prepares signal light using the in-path local oscillator method, the receiving end controls the polarization through a dynamic polarization controller, and then separates the local oscillator light from the quantum signal light through a polarization beam splitter, thereby obtaining the local oscillator light.

[0077] The local oscillator light generated by the laser at the receiving end, along with a signal light, enters a null or heterodyne detector for coherent detection.

[0078] For zero-difference detection:

[0079] For different substrates, the phase difference between the local oscillator light and the signal light is controlled by a phase modulator: for the substrate of the zero-difference detection at the receiver, the x component is used, and the phase difference between the local oscillator light and the signal light at the receiver is 0 degrees; for the substrate of the zero-difference detection receiver, the p component is used, and the phase difference between the local oscillator light and the signal light at the receiver is 90 degrees.

[0080] Next, the 3dB coupler outputs two optical signals, which are converted into photocurrents by photodiodes and then subtracted to obtain a differential current containing key information, which serves as the detection result at the receiving end.

[0081] For heterodyne detection:

[0082] By combining two zero-difference detectors, a heterodyne detector can be realized to simultaneously detect the two orthogonal components of a quantum signal. The heterodyne detector introduces a 90° phase shift in the path of the local oscillator, which can simultaneously detect the x and p orthogonal components of the quantum signal.

[0083] Step 4: The receiving end processes the coherent detection results to obtain the key information.

[0084] The specific process is as follows:

[0085] First, both sides perform basis selection: When the receiver uses homodyne detection, it randomly selects one component to probe during each measurement, obtaining the measurement result of a random canonical component. Each transmitter simultaneously possesses both components during modulation. Therefore, the receiver module needs to send its selected measurement basis to each transmitter via a classical channel. Each transmitter retains the data of the same basis, obtaining the original key related to the receiver. When the receiver uses heterodyne detection, it simultaneously obtains the measurement results of both canonical components of the quantum state, thus eliminating the need for a basis selection step.

[0086] Then, parameter estimation is performed. The sender and receiver calculate the covariance matrix by exchanging key data for a portion of the cycle, and use the covariance matrix to calculate the signal-to-noise ratio and security code rate. Depending on whether the security code rate meets the system's minimum requirements, it can be determined whether to perform data coordination, or terminate the post-processing flow, discard the data obtained in this round, and restart a new round of physical key distribution steps.

[0087] If the parameter estimation passes, the transmitters and receivers use the remaining data from the parameter estimation for data coordination. Data coordination involves the receiver using error-correcting codes to filter the obtained raw key and perform data error correction in a classical channel. During error correction, the checksum generated by the receiver during the error correction process is encrypted and transmitted on the classical channel using a one-time pad. Each transmitter performs its own correction upon receiving the checksum information.

[0088] After data negotiation is completed, a security enhancement process is needed to eliminate the presence of eavesdroppers and prevent information leakage. After security enhancement, the final security key can be obtained.

Claims

1. A continuous-variable quantum key distribution uplink networking device, characterized in that, The core is a 2×2 lossless bundle combining unit. By "cascading" or "binary tree" in the form of N lossless bundle combining units, a bundle combining system is formed, which ultimately combines multiple continuous variable quantum signals into one bundle to achieve lossless bundle combining. The 2×2 lossless beam combining unit includes two input ports, which are used to receive quantum signals from two different user transmitters; the first output port outputs the combined quantum signal, and the second output port outputs a signal of 0. The lossless beam combining unit includes phase shifters Φ and θ, as well as two 50:50 2×2 beam splitters. The quantum signal from the user transmitter is loaded onto the optical carrier through a modulator to form an optical signal. The phase real-time compensation module detects the phase difference between the input signals in real time and feeds it back to the first phase shifter Φ. By controlling the phase shifters Φ and θ, the relative phase of the two input optical signals is controlled. Finally, for any two input signals, by adjusting the phase shifters Φ and θ, one of the two outputs is the beam-combined signal and the other is 0.

2. The continuous variable quantum key distribution uplink networking device as described in claim 1, characterized in that, The process by which this device achieves lossless beam combining is as follows: A set of coherent light with arbitrary amplitude and phase is input through two input ports. By adjusting the first phase shifter Φ, the output light of this path is out of phase with the other normal input light signal. After the two inverted light signals pass through a 50:50 2×2 beam splitter, the amplitude of the light at the output end is adjusted by adjusting the second phase shifter θ. After the light signal and the other normal light signal pass through the 50:50 2×2 beam splitter, the output power of the second output port is reduced to 0. This is equivalent to combining the input light signals and outputting them all from the first output port, thus achieving coherent beam combining of the two input light signals.

3. The continuous variable quantum key distribution uplink networking device as described in claim 1, characterized in that, The cascaded networking structure first combines the optical signals from the two input ports of a lossless beam combiner into one beam, which is then used as the input of the next lossless beam combiner. This beam is then combined with other optical signals from the other port through a second lossless beam combiner, and so on, until all input light is finally combined into one beam through cascading.

4. The continuous variable quantum key distribution uplink networking device as described in claim 1, characterized in that, The binary tree networking structure refers to the process where every two incident beams are combined into one beam through a lossless beam combining unit, and each combined beam is then matched in pairs and combined into another lossless beam combining unit, ultimately combining all optical signals together.

5. An uplink networking system using the continuous variable quantum key distribution uplink networking device as described in claim 1, characterized in that, Specifically, it includes: First, each continuous variable quantum key distribution transmitter prepares optical signals using a local oscillator or a local oscillator scheme, and then sends the prepared optical signals to the uplink networking device through time-division multiplexing. The optical signals are then combined into one path through N-to-1 "cascade" or "binary tree" lossless beam combining structure and sent to the receiving end. At this point, in the uplink network of time-division multiplexed continuous-variable quantum key distribution, there is only one user input at a certain moment. At this time, the phase shift of phase shifter Φ is 0. By adjusting phase shifter θ, the splitting ratio of the two input beams between the output ports is changed. When the phase shift of phase shifter θ is π, it is equivalent to combining the input light signals and outputting them all from the second output port. The output power of the first output port is reduced to 0, i.e., E O1 =0, thereby achieving lossless output of the input optical signal, enabling this user to perform lossless beam combining with users at other times; Then, the receiving end generates or acquires the corresponding local oscillator light to receive and coherently detect the continuous variable quantum optical signal; finally, the coherent detection results are post-processed to obtain the key information.

6. The continuous variable quantum key distribution uplink networking system as described in claim 5, characterized in that, The different user terminal signal combination methods include time division multiplexing, and the time division multiplexing includes the distribution method of N user terminal signals in the time domain; in the time division multiplexing scheme, the transmitters of N user terminals transmit quantum signals to the node receiver in different time slots through optical delay modules, and the receiver receives and processes them in chronological order.

7. The continuous variable quantum key distribution uplink networking system as described in claim 6, characterized in that, The receiver obtains the data of the two canonical components of the quantum signal through time demultiplexing and coherent detection, and performs post-processing based on this data.

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