Interferometer-free quantum key distribution ring network

Abstract

The invention belongs to the technical field of optical secret communication, and discloses an interferometer-free quantum key distribution ring network, which is characterized in that when quantum key distribution is carried out between a central node and any intermediate node in the network, subcarrier signal modulation is carried out on the central node and the intermediate node, a random phase is added, and a symmetric key is generated; when quantum key distribution is carried out between any two intermediate nodes, the central node does not carry out phase modulation, the two intermediate nodes respectively carry out subcarrier signal modulation, and four random phases are added; after signal transmission and detection are completed, a central node publishes a measurement result, and then a symmetric key is generated. Compared with the prior art, quantum key distribution between any two nodes in the ring can be realized without a trusted relay, only phase modulation and light intensity monitoring are needed, an interferometer is not needed, a sending end and a receiving end do not need to be arranged at the same time, polarization compensation and phase compensation are not needed, resource consumption is reduced, and stability is improved; and the deployment and operation cost is greatly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of optical secure communication, and in particular to a quantum key distribution ring network without an interferometer. Background Art

[0002] With the development of science and technology and society, data and communication security are becoming more and more important. Quantum key distribution can provide information-theoretic security for both parties in communication and can be used to ensure the security of data transmission and communication. However, the key generation rate of the current quantum key distribution system cannot meet the growing encryption rate requirements.

[0003] In the existing quantum key distribution networking scheme, the nodes need to perform the quantum key distribution process separately in pairs. Conventional quantum key distribution devices distinguish between the sender and the receiver, so multiple devices need to be deployed at each node, and most of them use phase encoding schemes that require interferometers for encoding and decoding or polarization encoding schemes that require real-time polarization compensation, resulting in high networking costs and large occupied volume. In addition, in the conventional ring network structure, quantum key distribution cannot be performed directly between non-adjacent nodes, but the nodes between the two need to be used as trusted relays for secure key transmission. However, the premise of trusted relays is that the nodes are trusted, which greatly limits the actual security. Patent CN 115883089 B proposes a ring network structure, in which the same quantum key distribution device is deployed at each network node, which can be used as a sender and a receiver at the same time. However, the device structure in this scheme is complex, and the channel needs to be compensated for polarization and phase in real time, which increases the complexity and resource consumption of network equipment, and still requires trusted relays. Summary of the invention

[0004] In view of the above defects in the prior art, the present invention proposes a quantum key distribution ring network that does not require an interferometer.

[0005] The technical solution of the present invention is achieved in this way: A quantum key distribution ring network without interferometer, comprising N intermediate nodes and a central node, where N is an integer not less than 2; Each node contains an input port and an output port; The input ports and output ports of these N+1 adjacent nodes are connected through optical fiber channels to form a ring network. Specifically, each node is connected to each other through optical fiber channels; the output port and input port of the central node are respectively connected to the input port of the intermediate node 1 and the output port of the intermediate node N; the input port and output port of the intermediate node j are respectively connected to the output port of the intermediate node j-1 and the input port of the intermediate node j+1, 2≤j≤N-1; The central node is used to generate a narrow linewidth pulse optical signal, and is capable of performing subcarrier signal modulation on the pulse optical signal and attenuating it to the single photon level; and is used to filter the pulse optical signal input to its incident port, and use a single photon detector to detect the carrier signal and subcarrier signal generated by filtering; The intermediate node is used to modulate the input pulse optical signal with a carrier signal and output it after attenuating it to the single photon level; When quantum key distribution is performed between the central node and any intermediate node, both perform subcarrier signal modulation and add a random phase. After signal transmission and detection, basis vector comparison and post-processing are performed to generate a symmetric key. When quantum key distribution is performed between any two intermediate nodes, the central node does not perform phase modulation, and the two intermediate nodes respectively modulate the subcarrier signal and add random phases 0, π / 2, π, 3π / 2; after completing signal transmission and detection, the central node announces the measurement results, and then the two intermediate nodes perform basis vector comparison and post-processing operations to generate a symmetric key.

[0006] Preferably, the central node comprises a laser LD, an amplitude modulator AM, a first phase modulator PM1, a first adjustable attenuator VOA1, a circulator CIR, an optical fiber filter OF, a first single photon detector SPD1 and a second single photon detector SPD2, for generating a narrow linewidth continuous optical signal with a center frequency of ω; AM is used to modulate a continuous optical signal into a pulsed optical signal; PM1 is used to modulate the pulse optical signal by a subcarrier signal; VOA1 is used to attenuate the phase-modulated pulse optical signal to the single-photon level; The CIR is used to transmit the pulse optical signal incident to the input port of the central node to the OF, as well as the carrier optical signal to be reflected by the OF; SPD1 and SPD2 are used to detect the subcarrier optical signal and the carrier optical signal transmitted from the OF, respectively.

[0007] Preferably, the signal for subcarrier modulation performed by the central node and the intermediate node is , Ω is the subcarrier frequency, t is the time, and the modulation signal amplitude is satisfied , the random phase of each node satisfy .

[0008] Preferably, the intermediate node includes a phase modulation module, a second adjustable attenuator VOA2 and an optical intensity monitoring module, the phase modulation module is used for phase modulation of the subcarrier modulated signal, VOA2 is used for adjusting the output optical intensity, and the optical intensity monitoring module is used for real-time monitoring of the output optical intensity.

[0009] Preferably, the light intensity monitoring module of the intermediate node includes a beam splitter BS and a photodetector PD, the input port of the BS is connected to the output port of the VOA2; one output port of the BS is connected to the PD, and the other output port is directly output.

[0010] Preferably, the phase modulation module includes a first polarization beam splitter PBS1, a second polarization beam splitter PBS2, a second phase modulator PM2 and a third phase modulator PM3. The two output ports of PBS1 are connected to the two input ports of PBS2 through a polarization-maintaining optical fiber respectively. The two polarization-maintaining optical fibers are of equal length and are respectively provided with PM2 and PM3.

[0011] Preferably, the phase modulation module comprises a fourth phase modulator PM4 and a fifth phase modulator PM5, both of which can operate in dual axes, and the output port of PM4 is aligned with the input port of PM5 by 90° polarization rotation.

[0012] Compared with the prior art, the present invention has the following beneficial effects: The present invention proposes a quantum key distribution ring network that does not require an interferometer. It can realize quantum key distribution between any two nodes in the ring without a trusted relay. Each node has a simple structure and only needs to perform phase modulation and light intensity monitoring. There is no need to use an interferometer, there is no need to set up a transmitting end and a receiving end at the same time, and there is no need for polarization compensation and phase compensation, which reduces resource consumption, increases stability, and greatly reduces deployment and operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The schematic diagram of the quantum key distribution ring network without interferometer of the present invention; Figure 2 It is the principle diagram of the central node of the present invention; Figure 3 It is a schematic diagram of the subcarrier signal of the present invention in the frequency domain; Figure 4 is a schematic diagram of an intermediate node of the present invention; Figure 5 This is a schematic diagram of a first embodiment of a phase modulation module of the present invention; Figure 6 This is a schematic diagram of the second embodiment of the phase modulation module of the present invention. DETAILED DESCRIPTION

[0014] The present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0015] like Figure 1 As shown, a quantum key distribution ring network without interferometer includes N intermediate nodes and one central node, where N is an integer not less than 2; Each node contains an input port and an output port; The input ports and output ports of these N+1 adjacent nodes are connected through optical fiber channels to form a ring network. Specifically, each node is connected to each other through optical fiber channels; the output port and input port of the central node are respectively connected to the input port of the intermediate node 1 and the output port of the intermediate node N; the input port and output port of the intermediate node j are respectively connected to the output port of the intermediate node j-1 and the input port of the intermediate node j+1, 2≤j≤N-1; The central node is used to generate a narrow linewidth pulse optical signal, and is capable of performing subcarrier signal modulation on the pulse optical signal and attenuating it to the single photon level; and is used to filter the pulse optical signal input to its incident port, and use a single photon detector to detect the carrier signal and subcarrier signal generated by filtering; The intermediate node is used to modulate the input pulse optical signal with a carrier signal and output it after attenuating it to the single photon level; When quantum key distribution is performed between the central node and any intermediate node, both perform subcarrier signal modulation and add a random phase. After signal transmission and detection, basis vector comparison and post-processing are performed to generate a symmetric key. When quantum key distribution is performed between any two intermediate nodes, the central node does not perform phase modulation, and the two intermediate nodes respectively modulate the subcarrier signal and add random phases 0, π / 2, π, 3π / 2; after completing signal transmission and detection, the central node announces the measurement results, and then the two intermediate nodes perform basis vector comparison and post-processing operations to generate a symmetric key.

[0016] like Figure 2 As shown, the central node includes a laser LD, an amplitude modulator AM, a first phase modulator PM1, a first adjustable attenuator VOA1, a circulator CIR, an optical fiber filter OF, a first single photon detector SPD1 and a second single photon detector SPD2, which are used to generate a narrow linewidth continuous optical signal with a center frequency of ω; AM is used to modulate a continuous optical signal into a pulsed optical signal; PM1 is used to modulate the pulse optical signal by a subcarrier signal; VOA1 is used to attenuate the phase-modulated pulse optical signal to the single-photon level; The CIR is used to transmit the pulse optical signal incident to the input port of the central node to the OF, as well as the carrier optical signal to be reflected by the OF; SPD1 and SPD2 are used to detect the subcarrier optical signal and the carrier optical signal transmitted from the OF, respectively.

[0017] The signal for subcarrier modulation of the central node and the intermediate node is , Ω is the subcarrier frequency, t is the time, and the modulation signal amplitude is satisfied , the random phase of each node satisfy .

[0018] The intermediate node includes a phase modulation module, a second adjustable attenuator VOA2 and an optical intensity monitoring module. The phase modulation module is used for phase modulation of the subcarrier modulated signal, VOA2 is used for adjusting the output optical intensity, and the optical intensity monitoring module is used for real-time monitoring of the output optical intensity.

[0019] The light intensity monitoring module of the intermediate node includes a beam splitter BS and a photodetector PD. The input port of the BS is connected to the output port of VOA2; one output port of the BS is connected to the PD, and the other output port is directly output.

[0020] The specific working process is as follows: like Figure 2 As shown, the laser LD at the central node generates a narrow linewidth continuous optical signal with a central frequency of ω, which is modulated into a pulse optical signal by the amplitude modulator AM.

[0021] The central node can distribute quantum keys with any intermediate node, and any two intermediate nodes can also distribute quantum keys. The following are explained separately: (1) Quantum key distribution is performed between the central node and any intermediate node j. The pulse optical signal generated by the central node is modulated by the subcarrier signal through PM1 , where the additional random phase satisfies , then the subcarrier signal intensity is attenuated to the single photon level by VOA1, and the obtained optical signal is , Its schematic diagram in the frequency domain is as follows Figure 3 As shown, it includes a carrier signal with a center frequency of ω and two subcarrier signals with frequencies of ω±Ω, wherein the carrier signal serves as a strong reference signal and the subcarrier signal intensity is at the single photon level as a quantum state.

[0022] After passing through the optical fiber channel and other intermediate nodes between the output port of the central node and the input port of the intermediate node j, the quantum state enters the input port of the intermediate node j.

[0023] like Figure 4 As shown, at the intermediate node j, the quantum state is first modulated by the subcarrier signal through the phase modulation module , where the additional random phase satisfies , then passes through VOA2 without attenuation, and after passing through the fiber channel and other intermediate nodes between the output port of intermediate node j and the input port of the central node, it reaches the input port of the central node, and the quantum state becomes , Where η is the total channel loss and the loss of each intermediate node. It can be seen that the spectrum of the quantum state contains carrier signals and subcarrier signals.

[0024] when When , constructive interference occurs, and the quantum state passes through CIR and reaches OF and is filtered. The subcarrier signal enters SPD1 and the carrier signal enters SPD2. At this time, SPD1 responds and gets bit 1; when When the interference is canceled, the subcarrier signal is 0. After the quantum state passes through CIR and reaches OF and is filtered, no subcarrier signal enters SPD1, and the carrier signal enters SPD2. At this time, SPD1 does not respond, and bit 0 is obtained.

[0025] After completing signal transmission and detection, both parties perform basis vector comparison and post-processing operations to generate a symmetric key. At the intermediate node, a portion of the quantum state passes through the BS and enters the photodetector PD for detection. The light intensity passing through the intermediate node is monitored in real time to monitor whether there is an eavesdropper injecting Trojan light.

[0026] Although the polarization of the quantum state will change with environmental factors after passing through the optical fiber channel, the central node only needs to perform filtering and detection operations, which are independent of the polarization state, so there is no need for polarization compensation.

[0027] (2) Quantum key distribution is performed between intermediate nodes i and j. like Figure 2 As shown, the pulse optical signal generated by the central node passes through PM1 and VOA1 without phase modulation and attenuation, is emitted from the output port of the central node, enters the optical fiber channel, and reaches the intermediate node i after passing through several optical fiber channels and intermediate nodes.

[0028] like Figure 4 As shown, at the intermediate node i, the pulse optical signal is modulated by the phase modulation module to perform subcarrier signal modulation. , where the additional random phase satisfies , then the subcarrier signal intensity is attenuated to the single photon level by VOA2, and the obtained optical signal is , Its schematic diagram in the frequency domain is as follows Figure 3 As shown, it includes a carrier signal with a center frequency of ω and two subcarrier signals with frequencies of ω±Ω, wherein the carrier signal serves as a strong reference signal and the subcarrier signal intensity is at the single photon level as a quantum state.

[0029] After passing through the optical fiber channel and several intermediate nodes, the quantum state enters the input port of the intermediate node j. The quantum state is first modulated by the subcarrier signal through the phase modulation module. , where the additional random phase satisfies , then passes through VOA2 without attenuation, passes through the optical fiber channel and other intermediate nodes, and reaches the input port of the central node. The quantum state becomes , Where η is the total channel loss and the loss of each intermediate node. It can be seen that the spectrum of the quantum state contains carrier signals and subcarrier signals.

[0030] when When , constructive interference occurs, and the quantum state passes through CIR and reaches OF and is filtered. The subcarrier signal enters SPD1 and the carrier signal enters SPD2. At this time, SPD1 responds and gets bit 1; when When the interference is canceled, the subcarrier signal is 0. After the quantum state passes through CIR and reaches OF and is filtered, no subcarrier signal enters SPD1, and the carrier signal enters SPD2. At this time, SPD1 does not respond, and bit 0 is obtained.

[0031] After completing signal transmission and detection, both parties perform basis vector comparison and post-processing operations to generate a symmetric key. At the intermediate node, a portion of the quantum state passes through the BS and enters the photodetector PD for detection. The light intensity passing through the intermediate node is monitored in real time to monitor whether there is an eavesdropper injecting Trojan light.

[0032] Although the polarization of the quantum state will change with environmental factors after passing through the optical fiber channel, the central node only needs to perform filtering and detection operations, which are independent of the polarization state, so there is no need for polarization compensation.

[0033] like Figure 5 As shown, the first embodiment of the phase modulation module: The phase modulation module includes a first polarization beam splitter PBS1, a second polarization beam splitter PBS2, a second phase modulator PM2 and a third phase modulator PM3. The two output ports of PBS1 are connected to the two input ports of PBS2 through a polarization-maintaining optical fiber respectively. The two polarization-maintaining optical fibers are of equal length and are respectively provided with PM2 and PM3.

[0034] The specific working process is as follows: The quantum state of arbitrary polarization enters the input port of PBS1 and is divided into horizontal polarization component and vertical polarization component. The two components pass through the corresponding PM3 and PM2 respectively, and the subcarrier signal is modulated at the same time. Since the two have passed through the same length of polarization-maintaining fiber and the same phase modulation, the same phase change is generated. Therefore, the polarization state obtained after reaching PBS2 for polarization beam combining at the same time remains unchanged, and polarization-independent subcarrier phase modulation can be achieved.

[0035] like Figure 6 As shown, the second embodiment of the phase modulation module: The phase modulation module comprises a fourth phase modulator PM4 and a fifth phase modulator PM5, both of which can work in dual axes, and the output port of PM4 is aligned with the input port of PM5 by 90° polarization rotation.

[0036] The specific working process is as follows: The quantum state of arbitrary polarization enters the input port of PM4, and its horizontal polarization component and vertical polarization component enter PM4 respectively to become TE polarization mode and TM polarization mode. After the two are modulated by subcarrier signals, due to the existence of birefringence effect, the additional phases of the two polarization modes are different, so the obtained subcarrier signals can be written as and After 90° polarization rotation, it enters PM5. After the same subcarrier modulation, the phases of the two polarization components can be written as and It can be seen that the two polarization components are modulated with the same phase, so , polarization-independent subcarrier phase modulation can be achieved.

[0037] It can be seen from the various embodiments of the present invention that the present invention proposes a quantum key distribution ring network that does not require an interferometer. It does not require a trusted relay to achieve quantum key distribution between any two nodes in the ring. Each node has a simple structure and only needs to perform phase modulation and light intensity monitoring. There is no need to use an interferometer, there is no need to set up a transmitting end and a receiving end at the same time, and there is no need for polarization compensation and phase compensation, which reduces resource consumption, increases stability, and greatly reduces deployment and operating costs.

Claims

1. A quantum key distribution ring network without interferometer, characterized in that: It includes N intermediate nodes and one central node, where N is an integer not less than 2; Each node contains an input port and an output port; The input ports and output ports of these N+1 adjacent nodes are connected via optical fiber channels to form a ring network; The central node is used to generate a narrow linewidth pulse optical signal, and is capable of performing subcarrier signal modulation on the pulse optical signal and attenuating it to the single photon level; and is used to filter the pulse optical signal input to its incident port, and use a single photon detector to detect the carrier signal and subcarrier signal generated by filtering; The intermediate node is used to modulate the input pulse optical signal with a carrier signal and output it after attenuating it to the single photon level; When quantum key distribution is performed between the central node and any intermediate node, both perform subcarrier signal modulation and add a random phase. After signal transmission and detection, basis vector comparison and post-processing operations are performed to generate a symmetric key. When quantum key distribution is performed between any two intermediate nodes, the central node does not perform phase modulation, and the two intermediate nodes respectively modulate the subcarrier signal and add random phases 0, π / 2, π, 3π / 2; after completing signal transmission and detection, the central node announces the measurement results, and then the two intermediate nodes perform basis vector comparison and post-processing operations to generate a symmetric key.

2. The interferometer-free quantum key distribution ring network according to claim 1, characterized in that: The central node includes a laser LD, an amplitude modulator AM, a first phase modulator PM1, a first adjustable attenuator VOA1, a circulator CIR, an optical fiber filter OF, a first single photon detector SPD1 and a second single photon detector SPD2, and is used to generate a narrow linewidth continuous optical signal with a center frequency of ω; AM is used to modulate a continuous optical signal into a pulsed optical signal; PM1 is used to modulate the pulse optical signal by a subcarrier signal; VOA1 is used to attenuate the phase-modulated pulse optical signal to the single-photon level; The CIR is used to transmit the pulse optical signal incident to the input port of the central node to the OF, as well as the carrier optical signal to be reflected by the OF; SPD1 and SPD2 are used to detect the subcarrier optical signal and the carrier optical signal transmitted from the OF, respectively.

3. The interferometer-free quantum key distribution ring network according to claim 1, characterized in that: The signal for subcarrier modulation of the central node and the intermediate node is , Ω is the subcarrier frequency, t is the time, and the modulation signal amplitude is satisfied , the random phase of each node satisfy .

4. The interferometer-free quantum key distribution ring network as claimed in claim 2, characterized in that: The intermediate node includes a phase modulation module, a second adjustable attenuator VOA2 and an optical intensity monitoring module. The phase modulation module is used for phase modulation of the subcarrier modulated signal, VOA2 is used for adjusting the output optical intensity, and the optical intensity monitoring module is used for real-time monitoring of the output optical intensity.

5. The interferometer-free quantum key distribution ring network as claimed in claim 4, characterized in that: The light intensity monitoring module of the intermediate node includes a beam splitter BS and a photodetector PD. The input port of the BS is connected to the output port of VOA2; one output port of the BS is connected to the PD, and the other output port is directly output.

6. The interferometer-free quantum key distribution ring network as claimed in claim 4, characterized in that: The phase modulation module includes a first polarization beam splitter PBS1, a second polarization beam splitter PBS2, a second phase modulator PM2 and a third phase modulator PM3. The two output ports of PBS1 are connected to the two input ports of PBS2 through a polarization-maintaining optical fiber respectively. The two polarization-maintaining optical fibers are of equal length and are respectively provided with PM2 and PM3.

7. The interferometer-free quantum key distribution ring network as claimed in claim 4, characterized in that: The phase modulation module comprises a fourth phase modulator PM4 and a fifth phase modulator PM5, both of which can work in dual axes, and the output port of PM4 is aligned with the input port of PM5 by 90° polarization rotation.

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