CN115529079A - Signal state and decoy state average photon number online detection device and method - Google Patents
Signal state and decoy state average photon number online detection device and method Download PDFInfo
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- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
- H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
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- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
- H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
- H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
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- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
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Abstract
The invention provides a device and a method for detecting the average photon number of signal states and spoofing states at a transmitting end of quantum key distribution equipment on line, wherein the total output light power P of the transmitting end is utilized work Signal state light emission frequency freq s The frequency freq of light emission in decoy state d Calculating the mean photon number G and the mean photon number of decoy state by using the single pulse intensity ratio sd of signal state and decoy state and the optical wavelength lambda
The detection of the average photon number of the signal state and the decoy state can be directly finished when the quantum key distribution equipment works normally without changing the working state of the quantum key distribution equipment (especially the working of a laser and an intensity modulation unit)Frequency) and does not depend on the data reported by the measured sub-key distribution equipment and the single-photon detector, so that the whole test process is visual and credible, and the measurement accuracy is not influenced by the detection efficiency measurement accuracy and fluctuation of the single-photon detector.
Description
Technical Field
The invention relates to the technical field of quantum secret communication, in particular to the field of quantum security evaluation of quantum key distribution equipment, and specifically relates to a device and a method for online detection of signal state and decoy state average photon number.
Background
Quantum Key Distribution (QKD) is based on the quantum mechanics principle, and is a key distribution system that can be theoretically proven unconditionally safe due to the quantum unclonable and inaccurate measurement principle. The decoy state protocol allows quantum key distribution equipment to use weak coherent light in principle without using a single photon source with extremely high technical complexity and cost. In the spoof state protocol, it is required that the quantum key distribution device be capable of randomly modulating a specific average photon number, for example, the average photon number per pulse of a signal state
And average number of photons per pulse of decoy state
Is generally required to satisfy
The relationship (c) in (c). In the process, whether the signal state and the average photon number per pulse of the decoy state actually output by the quantum key distribution equipment meet the design indexes or not is safe with respect to the key, and if the average photon number per pulse actually output by the equipment deviates from the design value, the key leakage can be caused. For this reason, it is important to accurately detect the signal state and the average number of photons per pulse of the decoy state output by the quantum key distribution device.
Because the average photon number per pulse output by the quantum key distribution equipment is lower than 1, the output light intensity is very weak, usually in the magnitude of 100pW, even weaker, and the measurement cannot be directly carried out by using an oscilloscope after the conversion is carried out by a photoelectric probe. At present, the following schemes are mainly adopted:
the first scheme is to prepare all states as signal states and measure the average light using an optical power meterPower Ps, solved for knowing the emission frequency Freq and wavelength
Preparing all states as decoy states, measuring average optical power Pd by using an optical power meter, and solving under the condition of known luminous frequency Freq and wavelength
The second scheme is to randomly prepare a signal state and a decoy state during encoding, but record the encoding time sequence of the signal state and the decoy state, so that whether the Ti time encoding is the signal state or the decoy state can be known, and the number S of signal state encoding times and the number D of decoy state encoding times in { T1, T2, …, ti, …, tn } time are known. And detecting the coded and output light pulse by using a single-photon detector, recording the response of the corresponding moment, and counting the sum CNTsig of the response times corresponding to the signal state coding moment and the sum CNTdecoy of the response times corresponding to the decoy state coding moment in the moments (T1, T2, …, ti, … and Tn). Finally, measuring and acquiring the detection efficiency eta of the single photon detector, thereby obtaining the detection efficiency eta according to a formula
Obtaining the average photon number per pulse of the signal state, and calculating according to the formula
And acquiring the average photon number per pulse of the decoy state.
However, in the first scheme, since the operating frequencies of the laser and the intensity modulation unit in the average photon number measuring process are different from those in the actual system operation, which may cause the difference between the driving voltage amplitudes of the laser light emitting power and the intensity modulation unit and those in the actual system operation, the test result is deviated from that in the actual system operation, and the average photon number per pulse of the signal state and the spoofing state in the actual system operation cannot be accurately measured. In the second scheme, the measurement result of the average photon number depends on the accuracy of single photon detection efficiency, the single photon detection efficiency is difficult to calibrate, and the detection efficiency has certain fluctuation, which affects the accuracy of the measurement result; secondly, the measurement result of the average photon number also depends on real-time data provided by the tested equipment, so that the real-time data reported by the equipment in real time is required when the equipment is tested by using the scheme, the test is not visual enough, and the confidence of the test result needs to be established under the condition of ensuring the accuracy and the reality of the reported parameters of the equipment.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a device and a method for detecting the signal state and the average photon number in the decoy state on line at the transmitting end of quantum key distribution equipment, wherein the total output light power P of the transmitting end is utilized work Signal state light emission frequency freq s And a decoy state light emission frequency freq d Calculating the average photon number of the signal state from the single pulse intensity ratio sd of the signal state and the decoy state and the optical wavelength lambda
And the average number of photons in the decoy state
The detection of the signal state and the decoy state average photon number can be directly finished when the quantum key distribution equipment normally works, the working state (especially the working frequency of a laser and an intensity modulation unit) of the quantum key distribution equipment does not need to be changed, and the data reported by the measured quantum key distribution equipment and the single-photon detector are not depended on, so that the whole testing process is visual and credible, and the measuring accuracy is not influenced by the detecting efficiency measuring accuracy and fluctuation of the single-photon detector.
Specifically, a first aspect of the present invention relates to an on-line detection apparatus for detecting the average number of photons in a signal state and a decoy state at a sending end of a quantum key distribution device, which includes a power detection unit, a light emitting frequency detection unit, a light intensity ratio detection unit, a wavelength detection unit, and a control unit;
the power detection unit is used for acquiring the total power of the output light of the signal state and the decoy stateP work ；
The light-emitting frequency detection unit is used for acquiring a signal state light-emitting frequency freq s And frequency freq of emission in decoy state d ；
The light intensity ratio detection unit is used for acquiring the monopulse intensity ratio sd of the signal state and the decoy state;
the wavelength detection unit is used for acquiring the optical wavelength lambda of the sending end of the quantum key distribution equipment;
the control unit is used for controlling the operation of the electronic device according to a formula
Using said total output light power P work Signal state light emission frequency freq s The frequency freq of light emission in decoy state d The single pulse intensity ratio sd of the signal state and the decoy state, and the optical wavelength lambda are calculated to calculate the average photon number of the signal state
And the average number of photons in the decoy state
Where h is the Planck constant and c is the speed of light in vacuum.
Further, the power detection unit includes an optical power meter; and/or the light-emitting frequency detection unit comprises a photoelectric probe and an oscilloscope; and/or the light intensity ratio detection unit comprises a photoelectric probe and an oscilloscope; and/or the wavelength detection unit comprises a spectrometer.
Furthermore, when the light-emitting frequency detection unit comprises a photoelectric probe and an oscilloscope, the photoelectric probe is used for respectively converting the signal state and the decoy state into a first electric signal and a second electric signal, the oscilloscope is used for detecting the first electric signal and the second electric signal so as to obtain the signal state light-emitting frequency freq according to the electric signal statistics by calling a statistical function or setting an amplitude statistical threshold value s And a decoy state emission frequency freq d 。
Further, when the light intensity ratio detecting unit includes a photo-electric probe and an oscilloscope, the photo-electric probe is used for converting the signal state and the spoofing state into the first and second electric signals, respectively, and the oscilloscope is used for detecting the first and second electric signals so as to allow recording of amplitudes of the first and second electric signals, and calculating a single pulse intensity ratio sd of the signal state and the spoofing state according to the amplitudes.
Preferably, the light intensity ratio detection unit further includes a variable optical attenuator disposed before the photoelectric probe, and is further configured to: and obtaining an attenuation value L1 of the adjustable optical attenuator when the amplitude displayed by the oscilloscope in the spoofing state is consistent with the recorded amplitude of the first electric signal, and obtaining an attenuation value L2 of the adjustable optical attenuator when the amplitude displayed by the oscilloscope in the signal state is consistent with the recorded amplitude of the second electric signal, and calculating the monopulse intensity ratio sd of the signal state and the spoofing state according to the absolute difference dL between the attenuation values L1 and L2. Wherein, optionally, the light intensity ratio detecting unit may be according to the formula sd =10 (dL/10) And calculating the monopulse intensity ratio sd of the signal state and the decoy state by using the absolute difference dL, wherein the unit of the absolute difference dL is dB.
Further, when the wavelength detection unit includes a spectrometer, the wavelength λ is a peak wavelength or a-3 dB center wavelength.
Optionally, the sending end of the quantum key distribution device includes a light source, a decoy state preparation unit and an attenuation unit; the power detection unit comprises a wavelength division multiplexer and an optical power meter, wherein the wavelength division multiplexer is used for demultiplexing the signal state and the decoy state from the optical pulse output by the sending end of the quantum key distribution equipment so as to be used for the optical power meter; or, the power detection unit includes an optical splitter and an optical power meter, where the optical splitter is configured to split an optical pulse output by a sending end of the quantum key distribution device into a first component and a second component, the first component is used to send to a receiving end of the quantum key distribution device, and the second component is used in the optical power meter; or, the power detection unit includes an optical splitter, a wavelength division multiplexer, and an optical power meter, where the optical splitter is configured to split an optical pulse output by a sending end of the quantum key distribution device into a first component and a second component, and send the first component and the second component to a receiving end of the quantum key distribution device and the wavelength division multiplexer, respectively, and the wavelength division multiplexer is configured to demultiplex the signal state and the spoof state from the second component, so as to be used in the optical power meter.
Preferably, the sending end of the quantum key distribution device comprises a light source, a decoy state preparation unit and an attenuation unit, and the light emitting frequency detection unit and/or the light intensity ratio detection unit are connected with the output port of the decoy state preparation unit or the test interface connected with the output port.
The second aspect of the invention relates to a signal state and deception state average photon number on-line detection method, which comprises a parameter acquisition step and an average photon number calculation step;
in the parameter obtaining step, the total output light power P of the sending end of the quantum key distribution equipment is obtained work Signal state light emission frequency freq s And a decoy state light emission frequency freq d The monopulse intensity ratio sd of the signal state and the decoy state, and the optical wavelength λ;
in the average photon number calculation step, the average photon number is calculated according to the formula
Using said total output light power P work And a signal state light emission frequency freq s The frequency freq of light emission in decoy state d The single pulse intensity ratio sd of the signal state and the decoy state, and the optical wavelength lambda are calculated to calculate the average photon number of the signal state
And the average number of photons in the decoy state
Where h is the Planck constant and c is the speed of light in vacuum.
Further, the signal state and the decoy state can be converted into a signal state and a decoy stateElectrical signal, and counting the electrical signal to obtain the signal state light emitting frequency freq s And a decoy state emission frequency freq d 。
Further, the signal state and the decoy state can be converted into an electric signal by an optical-electric probe, and/or the electric signal can be counted by a statistical function of an oscilloscope or an amplitude statistical threshold value.
Further, the monopulse intensity ratio sd of the signal state and the spoofing state can be obtained from the amplitude ratio of the electrical signals by converting the signal state and the spoofing state into the electrical signals.
Further, the signal state and the spoofing state can be converted into a first electric signal and a second electric signal by an optical probe, the first electric signal and the second electric signal are detected and recorded with an oscilloscope, and the single pulse intensity ratio sd of the signal state and the spoofing state can be obtained according to the amplitude ratio of the first electric signal and the second electric signal.
Preferably, the attenuation value L1 when the amplitude of the oscilloscope in the trap state is consistent with the recorded amplitude of the first electric signal can be obtained by adjusting the attenuation value of the variable optical attenuator arranged in front of the photoelectric probe, the attenuation value L2 when the amplitude of the oscilloscope in the signal state is consistent with the recorded amplitude of the second electric signal can be obtained, and the monopulse intensity ratio sd between the signal state and the trap state can be calculated according to the absolute difference dL between the attenuation values L1 and L2.
Optionally, the total output light power P is obtained work The method may further include the step of performing wavelength division multiplexing and/or light splitting on the optical pulse output by the sending end of the quantum key distribution device.
Drawings
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 shows an embodiment of an apparatus for on-line detection of average photon numbers of signal states and spoof states according to the present invention;
FIG. 2 shows another embodiment of the signal state and spoof state average photon number on-line detector in accordance with the present invention;
FIG. 3 shows another embodiment of the signal state and spoof state average photon number on-line detector according to the present invention;
fig. 4 shows still another embodiment of the signal state and spoof state average photon number on-line detecting device according to the present invention.
Detailed Description
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following examples are provided by way of illustration in order to fully convey the spirit of the invention to those skilled in the art to which the invention pertains. Accordingly, the present invention is not limited to the embodiments disclosed herein.
Fig. 1 shows a specific embodiment of the signal state and spoof state average photon number online detection apparatus according to the present invention, which can be used for online detection of the signal state and spoof state average photon number generated in the transmitting end of the quantum key distribution device.
As known to those skilled in the art, the quantum key distribution device sending end based on the decoy state scheme can comprise a light source, a decoy state preparation unit and an attenuation unit. Generally, a test interface may also be provided in the transmitting end, which is connected to an output port of the spoofed state preparing unit, such as shown in fig. 1.
According to the invention, the signal state and the cheating state average photon number online detection device can comprise a power detection unit, a light-emitting frequency detection unit, a light intensity ratio detection unit, a wavelength detection unit and a control unit.
The power detection unit is used for acquiring the total power P of the signal state and the decoy state output by the sending end of the quantum key distribution equipment work . Therefore, the power detection unit may be configured to connect to an output port of the transmitting end or a test interface connected thereto, such as shown in fig. 1.
As a specific embodiment, the power detection unit may include an optical power meter, such as shown in fig. 1.
The light-emitting frequency detection unit is used for acquiring a signal state light-emitting frequency freq s And a decoy state emission frequency freq d 。
As a specific embodiment, as shown in fig. 1, the light emitting frequency detecting unit may include a photo probe and an oscilloscope. The photoelectric probe is used for converting a signal state and a decoy state into electric signals, wherein the signal state corresponds to a first electric signal, and the decoy state corresponds to a second electric signal. Since the amplitudes of the signal state and the spoof state have a significant difference, the first and second electrical signals can be clearly distinguished according to the amplitude. The oscilloscope is used for detecting the first and the second electric signals so as to obtain the signal state luminous frequency freq according to the statistics of the first and the second electric signals s And a decoy state emission frequency freq d 。
In one example, the signal state light emitting frequency freq can be obtained according to the statistics of the first and second electric signals by calling a statistical function of the oscilloscope or setting an amplitude statistical threshold s And a decoy state emission frequency freq d 。
Preferably, the light emission frequency detection unit may be arranged to connect an output port of the spoof state preparing unit, for example, through a test interface (as shown in fig. 1), to obtain the signal state and the spoof state light pulses.
The light intensity ratio detection unit is used for acquiring the monopulse intensity ratio sd of the signal state and the decoy state.
As a specific embodiment, as shown in fig. 1, the light intensity ratio detecting unit may include a photo probe and an oscilloscope. The photoelectric probe is used for converting a signal state and a decoy state into electric signals, wherein the signal state corresponds to a first electric signal, and the decoy state corresponds to a second electric signal. The oscilloscope is used for detecting the first electric signal and the second electric signal so as to obtain the amplitude of the electric signals, and the single pulse intensity ratio sd of the signal state and the decoy state is calculated. For example, the ratio of the amplitude of the first electrical signal to the amplitude of the second electrical signal may be taken as the monopulse intensity ratio sd of the signal state and the spoof state.
Preferably, the light intensity ratio detection unit may be arranged to be connected to an output port of the spoof state preparing unit, for example, through a test interface (as shown in fig. 1), so as to obtain the signal state and the spoof state light pulses.
Preferably, the light emission frequency detecting unit and the light intensity ratio detecting unit may share a photo probe and an oscilloscope.
In a preferred embodiment, to reduce the requirement for the linearity of the photo probe, the optical intensity ratio detection unit may further comprise a (calibrated) variable optical attenuator, which is arranged in front of the photo probe. Therefore, in the preferred embodiment, the variable optical attenuator can be adjusted to obtain an attenuation value L1 of the variable optical attenuator when the amplitude of the oscilloscope displayed for the spoofed state is consistent with the amplitude of the signal state (before adjustment), and an attenuation value L2 of the variable optical attenuator when the amplitude of the oscilloscope displayed for the signal state is consistent with the amplitude of the spoofed state (before adjustment). Finally, the monopulse intensity ratio sd of the signal state and the spoofing state can be obtained from the absolute difference dL between the attenuation values L1 and L2. For example, when the unit of the attenuation value (or dL) is dB, it can be according to the formula sd =10 (dL/10) And calculating and acquiring the monopulse intensity ratio sd of the signal state and the decoy state by using the absolute difference dL.
The wavelength detection unit is used for acquiring the optical wavelength lambda (namely the wavelength of the signal state and the decoy state optical pulse) of the transmitting end. According to the present invention, the wavelength detection unit may be configured to connect, for example, an output port of the decoy state preparation unit through the test interface or with an output port of the transmitting end to acquire the optical pulse.
As a specific embodiment, the wavelength detection unit may include a spectrometer. Preferably, the wavelength λ may be a peak wavelength or a-3 dB center wavelength.
Number of light pulses per unit time (which can emit light at a frequency freq by signal state) s Expressed) and average number of photons per pulse
And the product of the single photon energy Ep is the signal state light pulse energy in unit time and the decoy state light pulse number in unit time (which can be determined by the decoy state light emitting frequency freq) d Expressed) and average number of photons per pulse
And the product of the single photon energy Ep is the decoy state light pulse energy in unit time, so the total output light power P of the sending end of the quantum key distribution equipment work Can be as follows:
therefore, the average photon number of the signal state can be further deduced
And the average photon number of decoy state
Wherein h is the Planck constant, c is the speed of light in vacuum,
the single pulse intensity ratio of the signal state and the decoy state.
Therefore, in the signal state and decoy state average photon number on-line detection device of the present invention, the total power P of the output light can be obtained by the power detection unit work Obtaining a signal state light emission frequency freq by a light emission frequency detection unit s And a decoy state emission frequency freq d The monopulse intensity ratio sd of the signal state and the decoy state is obtained by the light intensity ratio detection unit, the wavelength λ of the light from the transmitting end is obtained by the wavelength detection unit, and the control unit controls the wavelength detection unit to detect the wavelength λ of the light from the transmitting endAccording to the formula two, P is utilized work 、freq s 、freq d Sd and lambda, and calculating to obtain the average photon number of the signal state
And the average number of photons in the decoy state
In the on-line detection scheme of the average photon number of the signal state and the decoy state according to the invention, the luminescence frequency freq is generated due to the signal state s And a decoy state emission frequency freq d The wavelength lambda is usually stable, so that the single pulse intensity ratio sd of the signal state and the decoy state and the total power P of output light are monitored in real time without continuously monitoring the wavelength lambda work Allowing to further simplify the online detection process.
Fig. 2 shows another specific embodiment of the signal state and spoofed state average photon number on-line detection device according to the present invention, which is suitable for a quantum key distribution device adopting a wavelength division multiplexing design. For the sake of brevity, only the differences from the specific embodiment shown in fig. 1 will be described below, and the same contents will not be described again.
As shown in fig. 2, in this specific embodiment, the power detection unit may further include a demultiplexer for demultiplexing a signal state and a spoofing state from the optical pulses output from the transmitting end, so as to be used in the optical power meter.
At this time, the optical power measured by the optical power meter is P1, the insertion loss of the demultiplexer is IL1, and the total output optical power P can be obtained according to P1 and IL1 work . For example, P work ＝P1+IL1。
Fig. 3 shows another specific embodiment of the signal state and spoofed state average photon number online detection device according to the present invention, which is suitable for a quantum key distribution device that requires a transmitting end to connect to a receiving end for coding. Also for the sake of brevity, only the differences from the specific embodiment shown in fig. 1 will be described below, and the description of the same will not be repeated.
As shown in fig. 3, in this specific embodiment, the power detection unit may further include an optical splitter for splitting the optical pulse output from the transmitting end into a first component and a second component, where the first component is to be used for transmission to the receiving end, and the second component is to be used for the optical power meter.
In the example of fig. 3, the optical splitter may include an optical splitter, where a public end of the optical splitter is connected to the output port of the transmitting end, a first splitting end of the optical splitter is connected to the receiving end of the quantum key distribution device, and a second splitting end of the optical splitter is connected to the optical power meter.
At this time, the optical power measured by the optical power meter is P2, and the insertion loss from the common end to the second beam splitting end in the optical beam splitter is IL2, so that the total output optical power P can be obtained according to P2 and IL2 work . For example, P work ＝P2+IL2。
Fig. 4 shows another embodiment of the signal state and spoofed state average photon number online detection device according to the present invention, which is suitable for a quantum key distribution device that adopts a wavelength division multiplexing design and requires a transmitting end to connect to a receiving end for coding. Also for the sake of brevity, only the differences from the specific embodiment shown in fig. 1 will be described below, and the same will not be described again.
As shown in fig. 4, in this particular embodiment, the power detection unit may further include an optical splitter and a wavelength division multiplexer.
The optical splitter is used for splitting the optical pulse output by the transmitting end into a first component and a second component, wherein the first component is used for transmitting to the receiving end, and the second component is used for the optical power meter.
The demultiplexer is used for demultiplexing the signal state and the spoofing state from the second component for the optical power meter.
In the example of fig. 4, the optical splitter may include an optical splitter, a public end of which is connected to the output port of the transmitting end, a first beam splitting end of which is connected to the receiving end of the quantum key distribution device, and a second beam splitting end of which is connected to the optical power meter through the demultiplexer.
At this time, the optical power measured by the optical power meter is P3, the insertion loss of the demultiplexer is IL1, and the optical beam splitter is connected to the common lineThe insertion loss from the end to the second beam splitting end is IL2, and the total output light power P can be obtained according to P3, IL1 and IL2 work . For example, P work ＝P3+IL1+IL2。
In summary, by means of the online detection device for the average photon number in the signal state and the spoofing state, the working state of the quantum key distribution equipment does not need to be changed, particularly the working frequency of a laser and an intensity modulation unit in the quantum key distribution equipment does not need to be changed (the change will affect the accuracy of the measurement result), the detection of the signal state and the average photon number in the spoofing state can be directly completed when the quantum key distribution equipment normally works, and the signal state and the average photon number per pulse of the spoofing state when the quantum key distribution equipment actually works can be accurately measured. In addition, the invention does not depend on the data reported by the measured sub-key distribution equipment, the whole detection process can be finished by using a general instrument or equipment, and the whole test process is visual and credible and has better public credibility. In addition, the invention does not need to rely on the single-photon detector, so the measurement accuracy of the invention is not influenced by the measurement accuracy of the detection efficiency of the single-photon detector and the fluctuation of the detection efficiency of the single-photon detector.
For better understanding of the principle of the present invention, the signal state and decoy state average photon number on-line detection method of the present invention, which may include a parameter acquisition step and an average photon number calculation step, will be further described below with reference to fig. 1 to 4.
In the parameter obtaining step, for example, when the sending end of the quantum key distribution device normally works, the total power P of output light of the sending end can be obtained work Signal state light emission frequency freq s And a decoy state light emission frequency freq d The monopulse intensity ratio sd of the signal state and the decoy state, and the optical wavelength λ.
In the average photon number calculation step, the total power P of the obtained output light is utilized based on the formula II work Signal state light emission frequency freq s The frequency freq of light emission in decoy state d The single pulse intensity ratio sd of the signal state and the decoy state and the optical wavelength lambda are calculated to obtain the average photon number of the signal state
And the average number of photons in the decoy state
In a specific embodiment of the parameter obtaining step, the optical power meter may be used to measure the optical pulse output by the transmitting end to obtain the total output power P work 。
The signal state and the decoy state in the transmitting end can be converted into electric signals, and the signal state luminous frequency freq is obtained by counting the electric signals s And a decoy state emission frequency freq d . In one example, the signal state and the decoy state can be converted into a first electric signal and a second electric signal by an optoelectronic probe, and the first electric signal and the second electric signal are detected by an oscilloscope, so that the luminescence frequency freq of the signal state can be obtained by counting the first electric signal and the second electric signal s And a decoy state emission frequency freq d . Wherein, the occurrence frequency of the first and second electrical signals can be counted by means of a statistical function of the oscilloscope or by setting an amplitude statistical threshold value, so as to obtain the signal state luminous frequency freq s And frequency freq of emission in decoy state d 。
The signal state and the decoy state can be converted into electric signals, and the monopulse intensity ratio sd of the signal state and the decoy state can be obtained based on the amplitude ratio of the electric signals.
In one example, the signal state and the spoofing state can be converted into a first electrical signal and a second electrical signal by an optical probe, the first electrical signal and the second electrical signal are detected by an oscilloscope to obtain the amplitudes thereof, and finally the monopulse intensity ratio sd of the signal state and the spoofing state is obtained according to the amplitude ratio of the first electrical signal and the second electrical signal. Preferably, a variable optical attenuator can be arranged in front of the photoelectric probe, the variable optical attenuator is adjusted, an attenuation value L1 of the variable optical attenuator is recorded when the amplitude displayed by the oscilloscope in the trap state is consistent with the amplitude of the signal state (before adjustment), and an attenuation value L2 of the variable optical attenuator is recorded when the amplitude displayed by the oscilloscope in the signal state is consistent with the amplitude displayed by the oscilloscope in the trap state (before adjustment); then, according to the decayAnd subtracting an absolute difference dL between the L1 and the L2 to obtain a single pulse intensity ratio sd of the signal state and the decoy state. For example, when the unit of the attenuation value (or dL) is dB, the monopulse intensity ratio sd =10 of the signal state to the decoy state (dL/10) 。
A spectrometer may be used to obtain the wavelength of light λ at the transmitting end. Preferably, the wavelength λ may be a peak wavelength or a-3 dB center wavelength.
Further, the total power P of output light at the transmitting end is obtained work The method can further comprise the step of demultiplexing and/or splitting the optical pulse so as to be suitable for various application scenarios of the quantum key distribution equipment.
Although the present invention has been described in connection with the embodiments illustrated in the accompanying drawings, it will be understood by those skilled in the art that the embodiments described above are merely exemplary for illustrating the principles of the present invention and are not intended to limit the scope of the present invention, and that various combinations, modifications and equivalents of the above-described embodiments may be made by those skilled in the art without departing from the spirit and scope of the present invention.
Claims (16)
1. A signal state and decoy state average photon number on-line detection device for a sending end of quantum key distribution equipment comprises a power detection unit, a luminous frequency detection unit, a light intensity ratio detection unit, a wavelength detection unit and a control unit;
the power detection unit is used for acquiring the total power P of the output light in the signal state and the decoy state work ；
The light-emitting frequency detection unit is used for acquiring a signal state light-emitting frequency freq s And a decoy state emission frequency freq d ；
The light intensity ratio detection unit is used for acquiring the monopulse intensity ratio sd of the signal state and the decoy state;
the wavelength detection unit is used for acquiring the optical wavelength lambda of the sending end of the quantum key distribution equipment;
the control unit is used for controlling the operation of the electronic device according to a formula
Using the total power P of the output light work And a signal state light emission frequency freq s The frequency freq of light emission in decoy state d The single pulse intensity ratio sd of the signal state and the decoy state, and the optical wavelength lambda are calculated to calculate the average photon number of the signal state
And the average number of photons in the decoy state
Where h is the Planck constant and c is the speed of light in vacuum.
2. The signal state and decoy state average photon number on-line detecting device according to claim 1, wherein:
the power detection unit comprises an optical power meter; and/or the like, and/or,
the light-emitting frequency detection unit comprises a photoelectric probe and an oscilloscope; and/or the like, and/or,
the light intensity ratio detection unit comprises a photoelectric probe and an oscilloscope; and/or the like, and/or,
the wavelength detection unit includes a spectrometer.
3. The on-line signal state and spoofed state average photon number detection device as claimed in claim 2, wherein when said light emitting frequency detection unit comprises a photoelectric probe and an oscilloscope, said photoelectric probe is used to convert said signal state and spoofed state into a first and a second electrical signals, respectively, said oscilloscope is used to detect said first and second electrical signals, so as to obtain said signal state light emitting frequency freq according to said electrical signal statistics by calling a statistical function or setting an amplitude statistical threshold s And a decoy state emission frequency freq d 。
4. The signal state and spoofed state average photon number on-line detecting device as claimed in claim 2, wherein when said light intensity ratio detecting unit comprises a photo probe and an oscilloscope, said photo probe is used for converting said signal state and spoofed state into first and second electrical signals, respectively, said oscilloscope is used for detecting said first and second electrical signals so as to allow recording the amplitude values of said first and second electrical signals, and calculating the monopulse intensity ratio sd of said signal state and spoofed state according to said amplitude values.
5. The on-line detection device for signal state and spoofed state average photon number as recited in claim 4, wherein said light intensity ratio detection unit further comprises a variable optical attenuator disposed before said optical probe, and further configured to: and obtaining an attenuation value L1 of the adjustable optical attenuator when the amplitude displayed by the oscilloscope in the spoofing state is consistent with the recorded amplitude of the first electric signal, and obtaining an attenuation value L2 of the adjustable optical attenuator when the amplitude displayed by the oscilloscope in the signal state is consistent with the recorded amplitude of the second electric signal, and calculating the monopulse intensity ratio sd of the signal state and the spoofing state according to the absolute difference dL between the attenuation values L1 and L2.
6. The signal state and decoy state average photon number on-line detection device as claimed in claim 5, wherein the light intensity ratio detection unit is according to the formula sd =10 (dL/10) And calculating the monopulse intensity ratio sd of the signal state and the spoofing state by using the absolute difference dL, wherein the unit of the absolute difference dL is dB.
7. The on-line signal state and spoof state average photon count detecting device as claimed in claim 2, wherein the wavelength λ is a peak wavelength or a-3 dB center wavelength when the wavelength detecting unit includes a spectrometer.
8. The signal state and spoofed state average photon number online detection device as claimed in any one of claims 1-7, wherein the quantum key distribution equipment transmitting end comprises a light source, a spoofed state preparation unit and an attenuation unit; and the number of the first and second electrodes,
the power detection unit comprises a wavelength division multiplexer and an optical power meter, wherein the wavelength division multiplexer is used for demultiplexing the signal state and the decoy state from the optical pulse output by the sending end of the quantum key distribution equipment so as to be used for the optical power meter; alternatively, the first and second electrodes may be,
the power detection unit comprises an optical splitter and an optical power meter, wherein the optical splitter is used for splitting optical pulses output by a sending end of the quantum key distribution equipment into a first component and a second component, the first component is used for sending to a receiving end of the quantum key distribution equipment, and the second component is used for the optical power meter; alternatively, the first and second electrodes may be,
the power detection unit comprises an optical splitter, a wavelength division multiplexer and an optical power meter, wherein the optical splitter is used for splitting optical pulses output by a sending end of the quantum key distribution equipment into a first component and a second component to be respectively sent to a receiving end of the quantum key distribution equipment and the wavelength division multiplexer, and the wavelength division multiplexer is used for demultiplexing the signal state and the decoy state from the second component to be used for the optical power meter.
9. The on-line detection device for the signal state and the spoofed state average photon number according to any one of claims 1 to 7, wherein the sending end of the quantum key distribution equipment comprises a light source, a spoofed state preparation unit and an attenuation unit, and the light emitting frequency detection unit and/or the light intensity ratio detection unit are/is connected with an output port of the spoofed state preparation unit or a test interface connected with the output port.
10. An online detection method for average photon number of signal state and decoy state comprises a parameter acquisition step and an average photon number calculation step;
in the parameter obtaining step, the total output light power P of the sending end of the quantum key distribution equipment is obtained work Signal state light emission frequency freq s The frequency freq of light emission in decoy state d The monopulse intensity ratio sd of the signal state and the decoy state, and the optical wavelength λ;
in the average photon number calculation step, the average photon number is calculated according to the formula
Using said total output light power P work Signal state light emission frequency freq s And a decoy state light emission frequency freq d The single pulse intensity ratio sd of the signal state and the decoy state, and the optical wavelength lambda are calculated to calculate the average photon number of the signal state
And the average number of photons in the decoy state
Where h is the Planck constant and c is the speed of light in vacuum.
11. The on-line detection method for the average photon number of the signal state and the decoy state as claimed in claim 10, wherein the signal state luminescence frequency freq is obtained by converting the signal state and the decoy state into electric signals and counting the electric signals s And a decoy state emission frequency freq d 。
12. The on-line detection method for the average photon number of the signal state and the spoof state as claimed in claim 11, wherein the signal state and the spoof state are converted into the electric signals by an optical probe, and/or the electric signals are counted by a statistical function of an oscilloscope or an amplitude statistical threshold value is set.
13. The on-line detection method for the average photon number of the signal state and the spoof state as claimed in claim 10, wherein the single pulse intensity ratio sd of the signal state and the spoof state is obtained according to the amplitude ratio of the electrical signals by converting the signal state and the spoof state into the electrical signals.
14. The signal state and spoofed state average photon number on-line detecting method as claimed in claim 13, wherein the signal state and the spoofed state are converted into a first and a second electric signals by means of an optoelectronic probe, the first and the second electric signals are detected and recorded with an oscilloscope, and the single pulse intensity ratio sd of the signal state and the spoofed state is obtained according to the amplitude ratio of the first and the second electric signals.
15. The method for on-line detection of the average photon count in signal state and spoof state as claimed in claim 14, wherein further adjusting the attenuation value of a variable optical attenuator disposed in front of said optical probe to obtain an attenuation value L1 when the amplitude of said oscilloscope displayed in the spoof state is consistent with the amplitude of the recorded first electrical signal, obtaining an attenuation value L2 when the amplitude of said oscilloscope displayed in the signal state is consistent with the amplitude of the recorded second electrical signal, and calculating the ratio sd of the single pulse intensities of said signal state and spoof state according to the absolute difference dL between said attenuation values L1 and L2.
16. The on-line detection method for signal state and decoy state average photon number according to any one of claims 10-15, wherein the total power P of the output light is obtained work And the method also comprises the step of performing wavelength division multiplexing and/or light splitting on the optical pulse output by the sending end of the quantum key distribution equipment.
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