CN109039474B - Processing system and method for avoiding quantum channel interference caused by classical strong light - Google Patents
Processing system and method for avoiding quantum channel interference caused by classical strong light Download PDFInfo
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Abstract
The invention discloses a processing system for avoiding the interference of classical strong light on a quantum channel, which comprises a controller and a modulation device, wherein a detector of a receiver Bob of a QKD system is connected to the modulation device positioned at a classical light outlet through the controller, and in the process of starting the process of the QKD system, the noise count introduced by the detector of the receiver Bob of the QKD system is reduced by modulating the classical outlet light of the receiver Bob of the QKD system or Alice of a sender of the QKD system. The invention also discloses a processing method for avoiding the interference of classical strong light on the quantum channel. Compared with the prior art, the invention has the following advantages: 1. the tolerance of the quantum channel to the classical light intensity is improved under the condition of single-fiber bearing transmission, and the environmental adaptability is improved. 2. The dependence on narrow bandwidth filters is reduced.
Description
Technical Field
The invention relates to the technical field related to classical optical communication and quantum communication, in particular to a noise processing method in communication.
Background
In classical-quantum co-channel transmission, channel crosstalk and nonlinear noise generated by classical strong light in an optical fiber transmission link have certain influence on a Quantum Key Distribution (QKD) system, and the system can have an excessively high error rate and cannot form codes under severe conditions. In the existing technical scheme, single-fiber bearer transmission of a quantum channel and a classical channel is realized mainly by technologies such as classical light intensity attenuation, narrow-band filtering, time division multiplexing and time domain filtering, but is mainly limited to laboratory environment verification at present.
In the existing technical scheme, the noise of introducing classical highlight nonlinear noise into a quantum channel is reduced by the technologies of classical light intensity attenuation, narrow-band filtering, time division multiplexing, time domain filtering and the like: the excessive attenuation of the classical light intensity easily causes the increase of the error rate of classical light communication; the time division multiplexing technology has no certain feasibility in the existing classical optical communication network; narrow-band grating filtering (common 100G DWDM, 20G/50G FBG and narrower-band filter devices and the like) is commonly adopted in the narrow-band filtering technology, however, certain defects exist in the FBG process in China at present, the central wavelength drift phenomenon of the grating is easy to cause, especially, the excessive attenuation loss of a quantum channel is caused by the central wavelength drift of the narrow-band grating below a bandwidth of 20G, and therefore, the unstable factors of the devices are easy to introduce excessive loss to a QKD system, so that the code cannot be formed; in addition, the temporal filtering technique can improve the tolerability of the classical light intensity to a certain extent, but still needs to further improve the classical light tolerance intensity and the higher signal-to-noise ratio of the quantum channel in the actual system work.
Disclosure of Invention
The invention aims to solve the technical problem of providing a processing system and a method for avoiding the interference of classical strong light on a quantum channel, which can reduce the nonlinear noise count introduced in the work flow of a QKD system so as to tolerate higher classical light intensity.
The invention solves the technical problems through the following technical scheme: a processing system for avoiding quantum channel interference caused by classical strong light comprises a QKD system sender Alice, a receiver Bob, a QKD system sender classical optical communication device, a QKD system receiver classical optical communication device, a sender wavelength division multiplexing module and a receiver wavelength division multiplexing module, wherein the QKD system sender Alice and the QKD system sender classical optical communication device are both connected to the sender wavelength division multiplexing module, the sender wavelength division multiplexing module and the receiver wavelength division multiplexing module are connected through an optical fiber channel, the QKD system receiver Bob and the QKD system receiver classical optical communication device are both connected to the receiver wavelength division multiplexing module, the processing system further comprises a controller and a modulation device, a detector of the QKD system receiver Bob is connected to the modulation device positioned at a classical optical outlet end of the QKD system sender Alice or a classical optical outlet end of the QKD system receiver Bob through the controller, during the process start-up of the QKD system, the noise count introduced by the detector of the receiver Bob of the QKD system is reduced by modulating the classical exit light of the sender Alice of the QKD system or the classical exit light of the receiver Bob of the QKD system. The classical exit light direction can be transmitted in the same direction or in the opposite direction with the quantum signal of the QKD system, so that the classical exit light can possibly be emitted from the classical optical communication device of the QKD system sender and also can possibly be emitted from the classical optical communication device of the QKD system receiver, and the modulation device can be installed at the classical light exit of the QKD system sender Alice and also can be installed at the classical light exit of the QKD system receiver Bob, so that the classical exit light of the QKD system sender Alice or the classical exit light of the QKD system receiver Bob can be modulated.
As a preferred embodiment, the modulation occurs in the polarization feedback process of the QKD system startup procedure;
in the polarization feedback process of the starting process, the system sends H, P two kinds of linearly polarized light in a certain sequence and frequency period, when H path light is sent, counting and reporting are carried out on V path counting, a control signal is sent to a modulation device through a controller to modulate classical exit light until the modulation counting is optimal, then HV contrast polarization feedback of the system is carried out, P path light emitting test is carried out after a meeting contrast threshold value is reached, when P path light is emitted, reporting and counting are carried out on N path counting, a control signal is sent to the modulation device through the controller to modulate the classical exit light until the modulation counting is optimal, then PN contrast polarization feedback of the system is carried out, and the next process is carried out after the meeting contrast threshold value is reached.
As a preferred embodiment, the modulation occurs during the polarization feedback validation process of the QKD system startup procedure;
in the polarization feedback verification process, the system sends V, N two kinds of linearly polarized light in a certain sequence and frequency period, when the system sends V path light, the H path count is counted and reported, a control signal is sent to a modulation device through a controller to modulate classical exit light until the modulation count is optimal at the minimum, and then HV contrast polarization feedback verification of the system is carried out; and when N paths of lights are emitted, reporting statistics is carried out on P paths of counts, a controller issues a control signal to a modulation device to modulate classical exit light until the modulation count is optimal at the minimum, and then the polarization feedback verification of the PN contrast of the system is carried out.
As a preferred embodiment, the modulation occurs during a synchronous correction of the QKD system startup procedure;
in the synchronous correction process, the system sends H, V, P, N four kinds of linearly polarized light in a certain sequence and frequency period, before the H-path synchronous correction is executed, H-path light is not sent, H-path counting is preferentially counted and reported, a control signal is sent to a modulation device through a controller to modulate classical exit light, and H-path light emitting and synchronous correction processes are carried out until the modulation counting is minimum; the rest V/P/N flow is consistent with the H flow.
As a preferred embodiment, the controller is a DSP controller, but may also be a micro CPU such as a high-performance MCU, an ARM, and the like.
As a preferred embodiment, the modulation device is a polarization modulator, but of course, the modulation device may be other devices capable of implementing functions such as polarization scrambling and modulation.
As a preferred embodiment, the optical path transmitted to the receiver Bob of the QKD system is split by a polarization splitting component module, which is H, V, P, N four paths respectively corresponding to the four-path detectors, the output ends of the four-path detectors are connected to the controller, the corresponding detector counts are respectively counted and reported in the system modulation process, and the classical light outlet light intensity is actively modulated by combining the reported counts.
The invention also discloses a processing method for avoiding the interference of classical strong light on the quantum channel, wherein the output end of the detector of the receiver Bob of the QKD system is connected to the modulation device positioned at the classical light outlet through the controller, and the noise count introduced by the detector of the receiver Bob of the QKD system is reduced by modulating the classical outlet light in the process of starting the process of the QKD system.
As a preferred embodiment, the modulation occurs in the polarization feedback process of the QKD system startup procedure;
as a preferred embodiment, in the polarization feedback process of the starting process, the system sends H, P two kinds of linearly polarized light in a certain order and frequency period, when sending the H-path light, the counting and reporting of the V-path count are performed, the controller sends a control signal to the modulation device to modulate the classical exit light until the modulation count is optimal at the minimum, then the HV contrast polarization feedback of the system itself is performed, the P-path light emission test is performed after the satisfied contrast threshold is reached, wherein when the P-path light emission is performed, the reporting and counting of the N-path count are performed, the controller sends a control signal to the modulation device to modulate the classical exit light until the modulation count is optimal at the minimum, then the PN contrast polarization feedback of the system itself is performed, and the next process is performed after the satisfied contrast threshold is reached.
As a preferred embodiment, the modulation occurs during the polarization feedback validation process of the QKD system startup procedure;
in the polarization feedback verification process, the system sends V, N two kinds of linearly polarized light in a certain sequence and frequency period, when the system sends V path light, the H path count is counted and reported, a control signal is sent to a modulation device through a controller to modulate classical exit light until the modulation count is optimal at the minimum, and then HV contrast polarization feedback verification of the system is carried out; and when N paths of lights are emitted, reporting statistics is carried out on P paths of counts, a controller issues a control signal to a modulation device to modulate classical exit light until the modulation count is optimal at the minimum, and then the polarization feedback verification of the PN contrast of the system is carried out.
As a preferred embodiment, the modulation occurs during a synchronous correction of the QKD system startup procedure;
in the synchronous correction process, the system sends H, V, P, N four kinds of linearly polarized light in a certain sequence and frequency period, before the H-path synchronous correction is executed, H-path light is not sent, H-path counting is preferentially counted and reported, a control signal is sent to a modulation device through a controller to modulate classical exit light, and H-path light emitting and synchronous correction processes are carried out until the modulation counting is minimum; the rest V/P/N flow is consistent with the H flow.
In the preferred embodiment, in the system modulation process, the corresponding detector counts are respectively reported in a statistical manner, and the classical light outlet light intensity is actively modulated by combining the reported counts.
Compared with the prior art, the invention has the following advantages:
1. the tolerance of the quantum channel to the classical light intensity is improved under the condition of single-fiber bearing transmission, and the environmental adaptability is improved.
2. The dependence on narrow bandwidth filters (e.g., the risk of center wavelength drift problems due to the use of bandwidths less than or equal to 20 GHz) is reduced.
Drawings
FIG. 1 is a schematic structural diagram of a processing system for avoiding the interference of classical strong light on a quantum channel according to a first embodiment of the present invention;
FIG. 2 is a flowchart of a processing method for avoiding the interference of classical strong light on a quantum channel according to a first embodiment of the present invention;
fig. 3 is a schematic structural diagram of a processing system for avoiding the interference of classical strong light on a quantum channel according to a second embodiment of the present invention.
Detailed Description
The following examples are given for the detailed implementation and specific operation of the present invention, but the scope of the present invention is not limited to the following examples.
Example one
The processing scheme for avoiding the quantum channel interference caused by the classical strong light is a scheme based on classical light polarization modulation, mainly acts on the process starting process of the QKD system, and reduces the noise count introduced by the detector of the QKD receiver Bob by performing polarization modulation on the classical light outlet of the QKD sender Alice, thereby ensuring the normal process starting process of the QKD system.
The overall block diagram of the processing system for avoiding the quantum channel interference caused by the classical strong light is shown in fig. 1, and the processing system comprises a QKD system sending party Alice, a receiving party Bob, a classical optical communication equipment sending end Data Transceiver, a classical optical communication equipment receiving end Data Transceiver, a sending party wavelength division multiplexing module WDM, a receiving party wavelength division multiplexing module WDM, a DSP controller and a polarization modulator PC.
The QKD system transmitting side Alice and the classical optical communication equipment transmitting side Data transmitter are both connected to a transmitting side wavelength division multiplexing module WDM, the transmitting side wavelength division multiplexing module WDM is connected with a receiving side wavelength division multiplexing module WDM through an optical fiber channel, a QKD system receiving side Bob and the classical optical communication equipment receiving side Data transmitter are both connected to the receiving side wavelength division multiplexing module WDM, and a detector of the QKD system receiving side Bob is connected to a polarization modulator PC located at the classical optical communication equipment transmitting side Data transmitter through a DSP controller.
The wavelength division multiplexing module WDM of the sender mainly carries out single-fiber load-bearing multiplexing on lights of different channels of Alice of the sender and a DataTransceiver of a sending end of a classical optical communication device, and the polarization modulator PC is mainly used for carrying out polarization modulation on the classical exit light. The wavelength division multiplexing module WDM of the receiving party mainly demultiplexes the light of different channels of a transmitting party Alice borne by a single fiber and a Data Transceiver of a transmitting end of the classical optical communication equipment, the light of a quantum channel is transmitted to a QKD system receiving party Bob, and the classical optical communication Data is transmitted to a Data Transceiver of a receiving end of the classical optical communication equipment. The optical path transmitted to the receiver Bob of the QKD system is split into H, V, P, N four paths by a polarization beam splitting component module, the four paths correspond to the detectors D0, D1, D2 and D3, the polarization beam splitting component module comprises a first beam splitter, a second beam splitter and a third beam splitter, the optical path transmitted to the receiver Bob of the QKD system is firstly split into two paths by the first beam splitter, then the two paths are respectively split into two paths H, V and P, N by the second beam splitter and the third beam splitter, and the output ends of the detectors D0, D1, D2 and D3 are connected to the DSP controller.
Taking a decoy BB84 protocol as an example, the processing method for avoiding the interference of the classical strong light on the quantum channel provided by the invention is to perform polarization feedback modulation on the classical exit light in the starting process of the system process, because the quantum signal light is very weak in the processes of system polarization feedback and synchronous correction, the quantum signal light is more susceptible to the influence of nonlinear noise of the classical strong light on the quantum channel in the transmission of an optical fiber link, the counts of corresponding detectors D0, D1, D2 and D3 are counted and reported respectively in the processes of polarization feedback and synchronous correction of the system process, the classical strong light exit light is actively modulated by combining the reported counts, and the normal operation of the system process is ensured.
The feedback modulation is mainly completed in the processes of polarization feedback, polarization feedback verification and synchronous correction of the QKD process. The polarization feedback verification process refers to transmitting V, N lights along with the phase locked with the HV/PN polarization feedback stage to verify whether the V/H, N/P contrast ratio can also reach the contrast threshold respectively. The purpose of the synchronous correction process is to enable a sender Alice of the QKD system and a receiver Bob of the QKD system to work cooperatively, and to realize synchronization of the sender and the receiver by using synchronous light transmitted by a quantum channel, namely to measure the accurate delay position of a signal light pulse relative to the synchronous light pulse. As shown in fig. 2. In the process of starting polarization feedback after delayed scanning is finished, the system sends H, P two kinds of linearly polarized light in a certain sequence and frequency period, when H path light is sent, counting and reporting are carried out on V path counting, a control signal is sent to a polarization modulator PC through a DSP controller to modulate classical exit light until the modulation counting is optimal at the minimum, then HV contrast polarization feedback of the system is carried out, P path light emitting test is carried out after a satisfied contrast threshold value is reached, when P path light emitting, reporting and counting are carried out on N path counting, a control signal is sent to the polarization modulator PC through the DSP controller to modulate the classical exit light until the modulation counting is optimal at the minimum, then PN contrast polarization feedback of the system is carried out, and the next process is carried out after the satisfied contrast threshold value is reached.
In the polarization feedback verification process, the system sends V, N two kinds of linearly polarized light in a certain sequence and frequency period, when the system sends V path light, the H path count is counted and reported, a control signal is sent to a polarization modulator PC through a DSP controller to modulate classical exit light until the modulation count is optimal at the minimum, and then HV contrast polarization feedback verification of the system is carried out; and when N paths of lights are emitted, reporting statistics is carried out on P paths of counts, a control signal is sent to a polarization modulator PC through a DSP controller to modulate classical exit light until the modulation count is optimal at the minimum, and then the polarization feedback verification of the PN contrast of the system is carried out.
In the synchronous correction process, the system sends H, V, P, N four kinds of linearly polarized light in a certain sequence and frequency period, before the H-path synchronous correction is executed, H-path light is not sent, H-path counting is preferentially reported, a control signal is issued to a polarization modulator PC through a DSP controller to modulate classical exit light until the modulation counting is minimum (or modulation parameters are directly issued by referring to the process), and then H-path light emitting and synchronous correction processes are carried out; the rest V/P/N paths of flows are consistent with the H path of specific operation flows, wherein the modulation to the minimum count ensures that the classical light introduces the minimum noise on the basis of the dark count of the detector, and the influence of the classical light introduced noise on the QKD system flow is reduced.
Example two
The difference between this embodiment and the first embodiment is that the controller adopts an MCU, and the classical exit light direction is transmitted in a backward direction with the quantum signal of the QKD system, so that the overall block diagram of the processing system for avoiding the interference of the classical strong light on the quantum channel is shown in fig. 3, and the processing system includes a sender Alice and a Receiver Bob of the QKD system, a sending end DataTransceiver of the classical optical communication device located in the Receiver Bob, a receiving end Data Receiver of the classical optical communication device located in the sender Alice, a sending wavelength division multiplexing module WDM, a receiving wavelength division multiplexing module WDM, an MCU, and a polarization modulator PC.
The QKD system transmitting side Alice and the classical optical communication equipment receiving side Data Receiver are both connected to a transmitting side wavelength division multiplexing module WDM, the transmitting side wavelength division multiplexing module WDM is connected with a receiving side wavelength division multiplexing module WDM through an optical fiber channel, both the QKD system receiving side Bob and the classical optical communication equipment transmitting side Data Receiver are connected to the receiving side wavelength division multiplexing module WDM, and a detector of the QKD system receiving side Bob is connected to a polarization modulator PC located at the classical optical communication equipment transmitting side Data Receiver through an MCU.
The processing method of the processing system for avoiding the interference of the classical strong light on the quantum channel is completely the same as that of the first embodiment, except that the classical exit light is emitted from the classical optical communication equipment of the QKD system receiving party, and the modulation device is installed at the classical light exit of the QKD system receiving party Bob and modulates the classical exit light of the QKD system receiving party Bob.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (6)
1. A processing system for avoiding quantum channel interference caused by classical strong light comprises a QKD system sender Alice, a receiver Bob, a QKD system sender classical optical communication device, a QKD system receiver classical optical communication device, a sender wavelength division multiplexing module and a receiver wavelength division multiplexing module, wherein the QKD system sender Alice and the QKD system sender classical optical communication device are both connected to the sender wavelength division multiplexing module, the sender wavelength division multiplexing module and the receiver wavelength division multiplexing module are connected through an optical fiber channel, the QKD system receiver Bob and the QKD system receiver classical optical communication device are both connected to the receiver wavelength division multiplexing module, the processing system is characterized by further comprising a controller and a modulation device, a detector of the QKD system receiver Bob is connected to the modulation device positioned at the QKD system sender Alice classical optical outlet end or the QKD system receiver Bob optical outlet end through the controller, in the process of starting the process of the QKD system, the noise count introduced by a detector of a receiver Bob of the QKD system is reduced by modulating the classical exit light of Alice of a sender of the QKD system or the classical exit light of the receiver Bob end of the QKD system;
the modulation is completed in the processes of polarization feedback, polarization feedback verification and synchronous correction of the QKD system starting process;
in the polarization feedback process of the starting process, the system sends H, P two kinds of linearly polarized light in a certain sequence and frequency period, when the H path light is sent, the counting and reporting of the V path are carried out, a control signal is sent to a modulation device through a controller to modulate the classical exit light until the modulation counting is optimal, then the HV contrast polarization feedback of the system is carried out, the P path luminescence test is carried out after the meeting contrast threshold value is reached, when the P path luminescence is carried out, the reporting and counting of the N path counting are carried out, the control signal is sent to the modulation device through the controller to modulate the classical exit light until the modulation counting is optimal, then the PN contrast polarization feedback of the system is carried out, and the next process is carried out after the meeting contrast threshold value is reached;
in the polarization feedback verification process, the system sends V, N two kinds of linearly polarized light in a certain sequence and frequency period, when the system sends V path light, the H path count is counted and reported, a control signal is sent to a modulation device through a controller to modulate classical exit light until the modulation count is optimal at the minimum, and then HV contrast polarization feedback verification of the system is carried out; when N paths of lights are emitted, P paths of counts are reported and counted, a controller sends a control signal to a modulation device to modulate classical exit light until the modulation count is optimal at the minimum, and then the system carries out PN contrast polarization feedback verification;
in the synchronous correction process, the system sends H, V, P, N four kinds of linearly polarized light in a certain sequence and frequency period, before the H-path synchronous correction is executed, H-path light is not sent, H-path counting is preferentially counted and reported, a control signal is sent to a modulation device through a controller to modulate classical exit light, and H-path light emitting and synchronous correction processes are carried out until the modulation counting is minimum; the rest V/P/N flow is consistent with the H flow.
2. The processing system for avoiding the interference of classical strong light on the quantum channel as claimed in claim 1, wherein the controller is a DSP controller.
3. The processing system for avoiding classical strong light interference on quantum channels according to claim 1, wherein the modulation device is a polarization modulator.
4. The processing system for avoiding the interference of classical strong light on a quantum channel as claimed in claim 1, wherein a light path transmitted to a receiver Bob of the QKD system is split by a polarization splitting module, which has H, V, P, N four paths respectively corresponding to four-path detectors, output ends of the four-path detectors are connected to a controller, counts of the corresponding detectors are respectively counted and reported in a system modulation process, and the classical light outlet light intensity is actively modulated in combination with the reported counts.
5. A processing method for avoiding quantum channel interference caused by classical strong light is characterized in that the output end of a detector of a receiver Bob of a QKD system is connected to a modulation device positioned at a classical light outlet through a controller, and in the process of starting the process of the QKD system, noise count introduced by the detector of the receiver Bob of the QKD system is reduced by modulating the classical outlet light;
the modulation is completed in the processes of polarization feedback, polarization feedback verification and synchronous correction of the QKD system starting process;
in the polarization feedback process of the starting process, the system sends H, P two kinds of linearly polarized light in a certain sequence and frequency period, when the H path light is sent, the counting and reporting of the V path are carried out, a control signal is sent to a modulation device through a controller to modulate the classical exit light until the modulation counting is optimal, then the HV contrast polarization feedback of the system is carried out, the P path luminescence test is carried out after the meeting contrast threshold value is reached, when the P path luminescence is carried out, the reporting and counting of the N path counting are carried out, the control signal is sent to the modulation device through the controller to modulate the classical exit light until the modulation counting is optimal, then the PN contrast polarization feedback of the system is carried out, and the next process is carried out after the meeting contrast threshold value is reached;
in the polarization feedback verification process, the system sends V, N two kinds of linearly polarized light in a certain sequence and frequency period, when the system sends V path light, the H path count is counted and reported, a control signal is sent to a modulation device through a controller to modulate classical exit light until the modulation count is optimal at the minimum, and then HV contrast polarization feedback verification of the system is carried out; when N paths of lights are emitted, P paths of counts are reported and counted, a controller sends a control signal to a modulation device to modulate classical exit light until the modulation count is optimal at the minimum, and then the system carries out PN contrast polarization feedback verification;
in the synchronous correction process, the system sends H, V, P, N four kinds of linearly polarized light in a certain sequence and frequency period, before the H-path synchronous correction is executed, H-path light is not sent, H-path counting is preferentially counted and reported, a control signal is sent to a modulation device through a controller to modulate classical exit light, and H-path light emitting and synchronous correction processes are carried out until the modulation counting is minimum; the rest V/P/N flow is consistent with the H flow.
6. The method as claimed in claim 5, wherein in the system modulation process, the corresponding detector counts are reported statistically, and the classical light output intensity is actively modulated by combining the reported counts.
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| US9553677B1 (en) * | 2014-11-17 | 2017-01-24 | Sandia Corporation | Self-referenced continuous-variable quantum key distribution |
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