CN115529079B - Online detection device and method for average photon number of signal state and decoy state - Google Patents
Online detection device and method for average photon number of signal state and decoy state Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- 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
- H04L9/0852—Quantum cryptography
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- 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
- H04B10/0795—Performance monitoring; Measurement of transmission parameters
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- 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
- H04B10/0795—Performance monitoring; Measurement of transmission parameters
- H04B10/07955—Monitoring or measuring power
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- 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
- H04B10/0795—Performance monitoring; Measurement of transmission parameters
- H04B10/07957—Monitoring or measuring wavelength
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- 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
- H04B10/70—Photonic quantum communication
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Abstract
The invention provides a device and a method for detecting the average photon number of a signal state and a decoy state of a sending end of quantum key distribution equipment, wherein the average photon number of the signal state and the average photon number of the decoy state are calculated by utilizing the total power P work of output light of the sending end, the luminous frequency freq s of the signal state, the luminous frequency freq d of the decoy state, the single pulse intensity ratio sd of the signal state and the decoy state and the wavelength lambda of lightThe detection of the average photon number of the signal state and the decoy state can be directly completed when the quantum key distribution equipment works normally, the working state (especially the working frequency of a laser and an intensity modulation unit) of the quantum key distribution equipment is not required to be changed, and the data reported by the measured sub key distribution equipment and the single photon detector are not dependent, so that the whole testing process is visual and reliable, and the measuring accuracy is not influenced by the measuring accuracy of the detecting efficiency of the single photon detector and the fluctuation thereof.
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, in particular to a device and a method for detecting the average photon number of a signal state and a decoy state on line.
Background
Quantum Key Distribution (QKD) is based on quantum mechanics principles, which are key distribution systems theoretically verifiable for unconditional security due to quantum unclonable and mismeasurable principles. The decoy-state protocol allows the quantum key distribution device to use weak coherent light in principle, without using a single photon source with extremely high technical complexity and cost. In decoy-state protocols, it is desirable that the quantum key distribution device be capable of randomly modulating a particular average photon number, such as the average photon number per pulse of a signal stateAnd average photon count per pulse of decoyGenerally, it is required to satisfyIs a relationship of (3). 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 device accord with design indexes or not is related to the safety of the key, and if the average photon number per pulse actually output by the device deviates from the design values, key leakage can be caused. Therefore, it is important to accurately detect the average photon number per pulse of the signal state and 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, often on the order of 100pW, even weaker, and the measurement can not be carried out by using an oscilloscope after the conversion by the photoelectric probe. At present, the scheme mainly comprises the following steps:
the first approach is to prepare all states as signal states, measure the average optical power Ps using an optical power meter, solve for known luminescence frequency Freq and wavelength All states were prepared as decoy states, the average optical power Pd was measured using an optical power meter, and solved for knowing the frequency Freq and wavelength of light emitted
The second scheme is to randomly prepare the signal state and the decoy state at the time of encoding, but record the encoding time sequence of the signal state and the decoy state, so that whether the signal state or the decoy state is encoded at the time of Ti can be known, and the number S of signal state encoding times and the number D of decoy state encoding times in the time of { T1, T2, …, ti, …, tn } are known. And detecting the optical pulse output by the code by using a single photon detector, recording the response of the corresponding time, and counting the sum CNTsig of the response times of the corresponding signal state code time and the sum CNTdecoy of the response times of the corresponding decoy state code time in the { T1, T2, …, ti, …, tn } time. Finally, the detection efficiency eta of the single photon detector is measured and acquired, so that the formula can be adoptedObtaining the average photon number per pulse of the signal state and according to the formulaAn average photon number per pulse of the decoy is obtained.
However, in the first scheme, since the working frequencies of the laser and the intensity modulation unit in the average photon number measurement process are different from those in the actual system operation, the driving voltage amplitude of the laser light emitting power and the intensity modulation unit are different from those in the actual system operation, so that the test result is deviated from that in the actual system operation, and the signal state and the average photon number per pulse 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 certain fluctuation exists in the detection efficiency, so that the accuracy of the measurement result is influenced; and secondly, the measurement result of the average photon number also depends on real-time data provided by the tested equipment, so that the equipment needs to be subjected to real-time reporting of real-time data when the equipment is tested by using the scheme, the test is not intuitive, and the public trust of the test result needs to be established under the condition of ensuring that the reporting parameters of the equipment are accurate and real.
Disclosure of Invention
In view of the above problems in the prior art, the present invention provides an online detection device and method for average photon number of signal state and decoy state of a sending end of a quantum key distribution device, wherein the average photon number of signal state is calculated by using the total power P work of the output light of the sending end, the frequency freq s of signal state light emission, the frequency freq d of decoy state light emission, the ratio sd of single pulse intensities of signal state and decoy state, and the wavelength lambda of lightAnd average photon number of decoy statesThe detection of the average photon number of the signal state and the decoy state can be directly completed when the quantum key distribution equipment works normally, the working state (especially the working frequency of a laser and an intensity modulation unit) of the quantum key distribution equipment is not required to be changed, and the data reported by the measured sub key distribution equipment and the single photon detector are not dependent, so that the whole testing process is visual and reliable, and the measuring accuracy is not influenced by the measuring accuracy of the detecting efficiency of the single photon detector and the fluctuation thereof.
Specifically, a first aspect of the present invention relates to an on-line detection device for average photon number of signal state and decoy state of a transmitting end of a quantum key distribution device, which comprises 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 work of the output light in the signal state and the decoy state;
The luminous frequency detection unit is used for acquiring signal state luminous frequency freq s and decoy state luminous frequency freq d;
the light intensity ratio detection unit is used for acquiring the single pulse intensity ratio sd of the signal state and the decoy state;
The wavelength detection unit is used for acquiring the wavelength lambda of the light of the sending end of the quantum key distribution equipment;
The control unit is used for controlling the control unit according to the formula Calculating the average photon number of the signal state by using the total power P work of the output light, the signal state luminous frequency freq s, the decoy state luminous frequency freq d, the single pulse intensity ratio sd of the signal state and the decoy state and the light wavelength lambdaAnd average photon number of decoy statesWhere h is the Planck constant and c is the speed of light in vacuum.
Further, the power detection unit comprises an optical power meter; and/or the luminous 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.
Still further, when the light emitting frequency detection unit includes a photoelectric probe for converting the signal state and the spoofing state into first and second electric signals, respectively, and an oscilloscope for detecting the first and second electric signals so as to obtain the signal state light emitting frequency freq s and the spoofing state light emitting frequency freq d according to the electric signal statistics by calling a statistical function or setting an amplitude statistical threshold.
Further, when the light intensity ratio detecting unit includes a photo-electric probe for converting the signal state and the spoof state into first and second electric signals, respectively, and a scope for detecting the first and second electric signals so as to allow the magnitudes of the first and second electric signals to be recorded, and calculating the single pulse intensity ratio sd of the signal state and the spoof state from the magnitudes.
Preferably, the light intensity ratio detection unit further comprises a tunable optical attenuator provided before the photoelectric probe, and is further configured to: by adjusting the adjustable optical attenuator, an attenuation value L1 of the adjustable optical attenuator when the amplitude of the signal state display by the oscilloscope is consistent with the recorded first electric signal amplitude and an attenuation value L2 of the adjustable optical attenuator when the amplitude of the signal state display by the oscilloscope is consistent with the recorded second electric signal amplitude are obtained, and the monopulse intensity ratio sd of the signal state and the decoy state is calculated according to the absolute difference dL between the attenuation values L1 and L2. Wherein, optionally, the light intensity ratio detecting unit may calculate the single pulse intensity ratio sd of the signal state and the spoof state according to the formula sd=10 (dL/10) by using the absolute difference dL, where the absolute difference dL is expressed in 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 comprises a light source, a decoy state preparation unit and an attenuation unit; the power detection unit comprises a wavelength division demultiplexer and an optical power meter, wherein the wavelength division demultiplexer is used for demultiplexing the signal state and the decoy state from the optical pulse output by the transmitting end of the quantum key distribution equipment so as to be used for the optical power meter; or the power detection unit comprises an optical splitter and an optical power meter, wherein the optical splitter is used for splitting the optical pulse output by the sending end of the quantum key distribution device into a first component and a second component, the first component is used for being sent to the receiving end of the quantum key distribution device, and the second component is used for the optical power meter; or the power detection unit comprises an optical splitting device, a wavelength division demultiplexer and an optical power meter, wherein the optical splitting device is used for splitting an optical pulse output by a sending end of the quantum key distribution device into a first component and a second component to be respectively sent to a receiving end of the quantum key distribution device and the wavelength division demultiplexer, and the wavelength division demultiplexer is used for demultiplexing the signal state and the decoy state from the second component for use 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 luminous frequency detection unit and/or the luminous intensity ratio detection unit are/is connected with an output port of the decoy state preparation unit or a test interface connected with the decoy state preparation unit.
The second aspect of the invention relates to an online detection method for average photon numbers of signal states and decoy states, which comprises a parameter acquisition step and an average photon number calculation step;
In the parameter obtaining step, the total output light power P work, the signal state light-emitting frequency freq s, the decoy state light-emitting frequency freq d, the single pulse intensity ratio sd of the signal state and the decoy state and the light wavelength lambda of the sending end of the quantum key distribution equipment are obtained;
In the average photon number calculation step, the average photon number is calculated according to the formula Calculating the average photon number of the signal state by using the total power P work of the output light, the signal state luminous frequency freq s, the decoy state luminous frequency freq d, the single pulse intensity ratio sd of the signal state and the decoy state and the light wavelength lambdaAnd average photon number of decoy statesWhere h is the Planck constant and c is the speed of light in vacuum.
Further, the signal state light emission frequency freq s and the decoy state light emission frequency freq d may be obtained by converting the signal state and the decoy state into electrical signals and counting the electrical signals.
Still further, the signal states and spoofing states may be converted to electrical signals by means of an opto-electronic probe and/or counted by means of an oscillometric statistical function or by setting an amplitude statistical threshold.
Further, the monopulse intensity ratio sd of the signal state and the decoy state may be obtained from the amplitude ratio of the electric signals by converting the signal state and the decoy state into electric signals.
Further, the signal state and the decoy state can be converted into a first electric signal and a second electric signal by means of an optoelectronic probe, the first electric signal and the second electric signal are detected by means of an oscilloscope, the amplitude value is recorded, and the single pulse intensity ratio sd of the signal state and the decoy state is obtained according to the amplitude value ratio of the first electric signal and the second electric signal.
Preferably, the attenuation value L1 of the amplitude of the display of the oscillograph with respect to the decoy state is obtained by adjusting the attenuation value of the adjustable optical attenuator arranged in front of the photoelectric probe, the attenuation value L2 of the display of the oscillograph with respect to the signal state is obtained when the amplitude of the display of the oscillograph with respect to the signal state is consistent with the recorded first electric signal amplitude, and the monopulse intensity ratio sd of the signal state and the decoy state is calculated according to the absolute difference dL between the attenuation values L1 and L2.
Optionally, when the total power P work of the output light is obtained, the method may further include a step of demultiplexing and/or splitting the optical pulse output by the sending end of the quantum key distribution device.
Drawings
The following describes the embodiments of the present invention in further detail with reference to the drawings.
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 illustrates one embodiment of an on-line detection device for average photon numbers in signal and decoy states in accordance with the present invention;
FIG. 2 illustrates another embodiment of an on-line detection device for average photon numbers in signal and decoy states in accordance with the present invention;
FIG. 3 illustrates yet another embodiment of a signal state and decoy state average photon number online detection device according to the present invention;
fig. 4 shows yet another embodiment of an on-line detection device for average photon numbers in signal and decoy states 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 to fully convey the spirit of the invention to those skilled in the art to which the invention pertains. Thus, the present invention is not limited to the embodiments disclosed herein.
Fig. 1 shows a specific embodiment of an on-line detection device for signal states and average photon numbers of decoy states according to the present invention, which can be used for on-line detection of signal states and average photon numbers of decoy states generated in a transmitting end of a quantum key distribution device.
Those skilled in the art know that a quantum key distribution device transmitting end based on a decoy scheme may include a light source, a decoy preparation unit, and an attenuation unit. In general, a test interface may also be provided in the sender, which connects to the output port of the decoy preparation unit, as shown in fig. 1.
According to the invention, the signal state and decoy state average photon number online detection device can comprise 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 work of the signal state and the decoy state output by the sending end of the quantum key distribution equipment. The power detection unit may thus be arranged to be connected to the output port of the transmitting end or to a test interface connected thereto, for example as shown in fig. 1.
As a specific embodiment, the power detection unit may comprise 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 light-emitting frequency freq d.
As a specific embodiment, as shown in fig. 1, the light emitting frequency detection unit may include an opto-electronic probe and an oscilloscope. The photoelectric probe is used for converting a signal state and a decoy state into an electric signal, wherein the signal state corresponds to a first electric signal, and the decoy state corresponds to a second electric signal. Since the amplitude of the signal state and the decoy state have a significant difference, the first and second electrical signals can be significantly distinguished according to the amplitude. The oscilloscope is used for detecting the first and second electric signals so as to obtain a signal state luminous frequency freq s and a decoy state luminous frequency freq d according to the statistics of the first and second electric signals.
In one example, the signal state luminescence frequency freq s and the spoof state luminescence frequency freq d may be derived from the first and second electrical signal statistics by invoking a statistical function of the oscilloscope or setting an amplitude statistical threshold.
Preferably, the luminescence frequency detection unit may be arranged to connect the output port of the decoy state preparation unit, e.g. through a test interface (as shown in fig. 1), to obtain the signal state and the decoy state light pulses.
The light intensity ratio detection unit is used for acquiring the single pulse intensity ratio sd of the signal state and the decoy state.
As a specific embodiment, as shown in fig. 1, the light intensity ratio detection unit may include a photoelectric probe and an oscilloscope. The photoelectric probe is used for converting a signal state and a decoy state into an electric signal, 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 and second electric signals to acquire the amplitude of the electric signals, and is used for calculating the single pulse intensity ratio sd of the signal state and the decoy state. 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 single pulse intensity ratio sd of the signal state and the decoy state.
Preferably, the light intensity ratio detection unit may be arranged to connect the output port of the decoy state preparation unit, for example through a test interface (as shown in fig. 1), in order to obtain the signal state and the decoy state light pulses.
Preferably, the light emitting 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 linearity of the optoelectronic probe, the light intensity ratio detection unit may further comprise a (calibrated) adjustable light attenuator arranged in front of the optoelectronic probe. Thus, in this preferred embodiment, the adjustable optical attenuator may be adjusted to obtain an attenuation value L1 for the adjustable optical attenuator when the amplitude of the oscilloscope's display for the spoofed state is made to coincide with the amplitude of the signal state (before adjustment), and an attenuation value L2 for the adjustable optical attenuator when the amplitude of the oscilloscope's display for the signal state is made to coincide with the amplitude of the spoofed state (before adjustment). Finally, the monopulse intensity ratio sd of the signal state and the decoy state can be obtained from the absolute difference dL of the attenuation values L1 and L2. For example, when the attenuation value (or dL) is in dB, the monopulse intensity ratio sd of the signal state and the spoof state may be obtained by calculation using the absolute difference dL according to the formula sd=10 (dL/10).
The wavelength detection unit is used for acquiring the wavelength lambda (namely the wavelength of the signal state and the decoy state light pulse) of the transmitting end. According to the invention, the wavelength detection unit may be arranged to be connected to the output port of the decoy preparation unit, for example by a test interface, or to the output port of the transmitting end, to obtain the light pulses.
As a specific embodiment, the wavelength detection unit may comprise a spectrometer. Preferably, the wavelength λ may be a peak wavelength or a-3 dB center wavelength.
Due to the number of signal state light pulses per unit time (which may be represented by signal state light emission frequency freq s) and the average photon number per pulseAnd the product of the single photon energy Ep is the signal state light pulse energy per unit time, the number of decoy state light pulses per unit time (which may be represented by the decoy state light emission frequency freq d) and the average photon number per pulseAnd the product of the single photon energy Ep is the decoy state optical pulse energy in unit time, so the total output optical power P work of the sending end of the quantum key distribution device can be:
from this, the average photon number of signal state can be further deduced And average photon number of decoy states
Where h is the Planck constant, c is the speed of light in vacuum,The ratio of single pulse intensities for the signal and decoy states.
Thus, in the signal state and decoy state average photon number online detection device of the present invention, the total power P work of the output light can be obtained by means of the power detection unit, the signal state light emission frequency freq s and the decoy state light emission frequency freq d are obtained by means of the light emission frequency detection unit, the single pulse intensity ratio sd of the signal state and the decoy state is obtained by means of the light intensity ratio detection unit, the light wavelength lambda of the transmitting end is obtained by means of the wavelength detection unit, and the signal state average photon number is calculated by the control unit according to the formula II using P work、freqs、freqd, sd and lambdaAnd average photon number of decoy states
In the signal state and decoy state average photon number online detection scheme according to the present invention, since the signal state light emission frequency freq s and the decoy state light emission frequency freq d, the wavelength λ is generally stable, it is not necessary to continuously monitor them, and only the single pulse intensity ratio sd and the total output light power P work of the signal state and the decoy state need to be monitored in real time, thereby allowing further simplification of the online detection process.
Fig. 2 shows another specific embodiment of a signal state and decoy state average photon number online detection device according to the present invention, which is suitable for a quantum key distribution apparatus employing a wavelength division multiplexing design. For the sake of brevity, only the content different from the specific embodiment shown in fig. 1 will be described hereinafter, and the same content will not be described in detail.
As shown in fig. 2, in this specific embodiment, the power detection unit may further include a demultiplexer for demultiplexing the signal state and the decoy state from the optical pulse output from the transmitting end for the optical power meter.
At this time, when the optical power measured by the optical power meter is P1 and the insertion loss of the demultiplexer is IL1, the total output optical power P work can be obtained from P1 and IL1. For example, the number of the cells to be processed, P work = P1+IL1.
Fig. 3 shows a further specific embodiment of an on-line detection device for average photon numbers in signal states and decoy states according to the present invention, which is suitable for a quantum key distribution device requiring a transmitting end to be connected to a receiving end for encoding. Also for the sake of brevity, only the content different from the specific embodiment shown in fig. 1 will be described below, and the same content will not be described in detail.
As shown in fig. 3, in this specific embodiment, the power detection unit may further include a light splitting device for splitting the optical pulse output from the transmitting end into a first component and a second component, wherein the first component is to be transmitted 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, a common end of which is connected to an output port of the transmitting end, a first splitting end is connected to a receiving end of the quantum key distribution device, and a second splitting end 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 work can be obtained from P2 and IL2. For example, the number of the cells to be processed, P work = P2+il2.
Fig. 4 shows a further embodiment of an on-line detection device for average photon numbers in signal and decoy states according to the present invention, which is suitable for a quantum key distribution device employing a wavelength division multiplexing design and requiring a transmitting end to be connected to a receiving end for encoding. Also for the sake of brevity, only the content different from the specific embodiment shown in fig. 1 will be described hereinafter, and the same content will not be described again.
In this particular embodiment, the power detection unit may further include an optical splitter and a demultiplexer, as shown in fig. 4.
The light splitting device 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 being transmitted to the receiving end, and the second component is used for the optical power meter.
The demultiplexer is used to demultiplex the signal states and the decoy states from the second component for use in the optical power meter.
In the example of fig. 4, the optical splitter may include an optical splitter, a common end of which is connected to an output port of the transmitting end, a first splitting end is connected to a receiving end of the quantum key distribution device, and a second splitting end is connected to the optical power meter through a 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 insertion loss from the common end to the second beam splitting end in the optical splitter is IL2, so that the total output optical power P work can be obtained from P3, IL1, and IL2. For example, the number of the cells to be processed, P work =p3+ IL1+ IL2.
In summary, by means of the signal state and decoy state average photon number online detection device, the signal state and decoy state average photon number per pulse can be directly detected when the quantum key distribution device normally works, and the signal state and decoy state average photon number per pulse when the quantum key distribution device actually works can be accurately detected without changing the working state of the quantum key distribution device, particularly without changing the working frequency of a laser and an intensity modulation unit in the quantum key distribution device (the change can affect the accuracy of a measurement result). In addition, the invention does not depend on the data reported by the measured subkey distribution equipment, the whole detection process can be completed by using a universal instrument or equipment, and the whole test process is visual and reliable and has better public confidence. In addition, the invention does not depend on the single photon detector, so that the measurement accuracy of the invention is not influenced by the detection efficiency measurement accuracy of the single photon detector and the fluctuation of the detection efficiency of the single photon detector.
For a better understanding of the principles of the present invention, the signal state and decoy state average photon number online 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 in conjunction with fig. 1-4.
In the parameter obtaining step, for example, when the transmitting end of the quantum key distribution device is operating normally, the total output light power P work of the transmitting end, the signal state light emission frequency freq s, the 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 λ may be obtained.
In the average photon number calculation step, the average photon number of the signal state is calculated based on the formula II by using the obtained total power P work of the output light, the signal state light-emitting frequency freq s, the decoy state light-emitting frequency freq d, the single pulse intensity ratio sd of the signal state and the decoy state, and the light wavelength lambdaAnd average photon number of decoy states
In one embodiment of the parameter obtaining step, the optical pulse output by the transmitting end may be measured by using an optical power meter to obtain the total power P work of the output light.
The signal state and the decoy state in the transmitting end can be converted into electric signals, and the signal state light-emitting frequency freq s and the decoy state light-emitting frequency freq d are obtained by counting the electric signals. In one example, the signal and spoof states may be converted to first and second electrical signals by means of an optoelectronic probe, which are then detected by means of an oscilloscope in order to obtain the signal state luminescence frequency freq s and spoof state luminescence frequency freq d by statistically taking the first and second electrical signals. The frequency of occurrence of the first and second electrical signals may be counted by means of a counting function of an oscilloscope or by setting an amplitude counting threshold, so as to obtain the signal state light emitting frequency freq s and the decoy state light emitting frequency freq d.
The signal state and the decoy state may be converted into electrical signals, and the single pulse intensity ratio sd of the signal state and the decoy state may be obtained based on the amplitude ratio of the electrical signals.
In one example, the signal and spoof states may be converted into first and second electrical signals by means of an opto-electronic probe, which are then detected by means of an oscilloscope to obtain their magnitudes, and finally the single pulse intensity ratio sd of the signal and spoof states is obtained from the magnitude ratio of the first and second electrical signals. Preferably, an adjustable optical attenuator may be provided before the photoelectric probe, the adjustable optical attenuator is adjusted, an attenuation value L1 of the adjustable optical attenuator is recorded when the amplitude of the oscilloscope for the decoy state display is made to coincide with the signal state amplitude (before adjustment), and an attenuation value L2 of the adjustable optical attenuator is recorded when the amplitude of the oscilloscope for the signal state display is made to coincide with the decoy state amplitude (before adjustment); then, the monopulse intensity ratio sd of the signal state to the decoy state is obtained from the absolute difference dL of the attenuation values L1 and L2. For example, when the attenuation value (or dL) is in dB, the single pulse intensity ratio sd=10 (dL/10) of the signal state to the decoy state.
A spectrometer can be used to obtain the wavelength lambda of the light at the transmitting end. Preferably, the wavelength λ may be a peak wavelength or a-3 dB center wavelength.
Further, when the total power P work of the light output by the transmitting end is obtained, the method can further include a step of demultiplexing and/or splitting the light pulse, so as to be suitable for application scenarios of various quantum key distribution devices.
While the invention has been described in connection with the specific embodiments illustrated in the drawings, it will be readily appreciated by those skilled in the art that the above embodiments are merely illustrative of the principles of the invention, which are not intended to limit the scope of the invention, and various combinations, modifications and equivalents of the above embodiments may be made by those skilled in the art without departing from the spirit and scope of the invention.
Claims (16)
1. The device 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 work of the output light in the signal state and the decoy state;
The luminous frequency detection unit is used for acquiring signal state luminous frequency freq s and decoy state luminous frequency freq d;
the light intensity ratio detection unit is used for acquiring the single pulse intensity ratio sd of the signal state and the decoy state;
The wavelength detection unit is used for acquiring the wavelength lambda of the light of the sending end of the quantum key distribution equipment;
The control unit is used for controlling the control unit according to the formula Calculating the average photon number of the signal state by using the total power P work of the output light, the signal state luminous frequency freq s, the decoy state luminous frequency freq d, the single pulse intensity ratio sd of the signal state and the decoy state and the light wavelength lambdaAnd average photon number of decoy statesWhere h is the Planck constant, c is the speed of light in vacuum, and Ep is the single photon energy.
2. The signal state and decoy state average photon number online detection device of claim 1, wherein:
The power detection unit comprises an optical power meter; and/or
The luminous 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.
3. The signal state and decoy state average photon number online detection apparatus according to claim 2, wherein when the light emission frequency detection unit includes a photoelectric probe for converting the signal state and the decoy state into first and second electric signals, respectively, and an oscilloscope for detecting the first and second electric signals so as to statistically obtain the signal state light emission frequency freq s and the decoy state light emission frequency freq d from the electric signals by calling a statistical function or setting an amplitude statistical threshold.
4. The signal state and decoy state average photon number online detection apparatus as claimed in claim 2, wherein when the light intensity ratio detection unit comprises a photoelectric probe for converting the signal state and the decoy state into first and second electric signals, respectively, and an oscilloscope for detecting the first and second electric signals so as to allow the amplitude of the first and second electric signals to be recorded, and calculating a single pulse intensity ratio sd of the signal state and the decoy state from the amplitude.
5. The signal state and spoof state average photon number online detecting device of claim 4, wherein the light intensity ratio detecting unit further comprises a tunable optical attenuator disposed in front of the photoelectric probe, and further configured to: by adjusting the adjustable optical attenuator, an attenuation value L1 of the adjustable optical attenuator when the amplitude of the signal state display by the oscilloscope is consistent with the recorded first electric signal amplitude and an attenuation value L2 of the adjustable optical attenuator when the amplitude of the signal state display by the oscilloscope is consistent with the recorded second electric signal amplitude are obtained, and the monopulse intensity ratio sd of the signal state and the decoy state is calculated according to the absolute difference dL between the attenuation values L1 and L2.
6. The online detection apparatus for average photon numbers in signal states and decoy states as claimed in claim 5, wherein the light intensity ratio detection unit calculates the single pulse intensity ratio sd of the signal states and the decoy states using the absolute difference dL in dB according to the formula sd=10 (dL/10).
7. The signal state and decoy state average photon number online detection device according to claim 2, wherein the wavelength λ is a peak wavelength or a-3 dB center wavelength when the wavelength detection unit includes a spectrometer.
8. The online detection device for average photon numbers in signal states and decoy states according to any one of claims 1 to 7, wherein the transmitting end of the quantum key distribution equipment comprises a light source, a decoy state preparation unit and an attenuation unit; and
The power detection unit comprises a wavelength division demultiplexer and an optical power meter, wherein the wavelength division demultiplexer is used for demultiplexing the signal state and the decoy state from the optical pulse output by the transmitting end of the quantum key distribution equipment so as to be used for the optical power meter; or alternatively
The power detection unit comprises an optical splitter and an optical power meter, wherein the optical splitter is used for splitting an optical pulse 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 being sent to a receiving end of the quantum key distribution equipment, and the second component is used for the optical power meter; or alternatively
The power detection unit comprises an optical splitting device, a wavelength division demultiplexer and an optical power meter, wherein the optical splitting device is used for splitting an optical pulse output by a sending end of the quantum key distribution device into a first component and a second component to be respectively sent to a receiving end of the quantum key distribution device and the wavelength division demultiplexer, and the wavelength division demultiplexer is used for demultiplexing the signal state and the decoy state from the second component for use in the optical power meter.
9. The signal state and decoy state average photon number online detection device according to any one of claims 1-7, wherein the quantum key distribution equipment transmitting end comprises a light source, a decoy state preparation unit and an attenuation unit, and the luminous frequency detection unit and/or the luminous intensity ratio detection unit is connected with an output port of the decoy state preparation unit or a test interface connected with the same.
10. An online detection method for average photon numbers of signal states and decoy states comprises a parameter acquisition step and an average photon number calculation step;
In the parameter obtaining step, the total output light power P work, the signal state light-emitting frequency freq s, the decoy state light-emitting frequency freq d, the single pulse intensity ratio sd of the signal state and the decoy state and the light wavelength lambda of the sending end of the quantum key distribution equipment are obtained;
In the average photon number calculation step, the average photon number is calculated according to the formula Calculating the average photon number of the signal state by using the total power P work of the output light, the signal state luminous frequency freq s, the decoy state luminous frequency freq d, the single pulse intensity ratio sd of the signal state and the decoy state and the light wavelength lambdaAnd average photon number of decoy statesWhere h is the Planck constant, c is the speed of light in vacuum, and Ep is the single photon energy.
11. The on-line detection method of signal state and decoy state average photon number as claimed in claim 10, wherein the signal state light emission frequency freq s and the decoy state light emission frequency freq d are obtained by converting the signal state and the decoy state into an electrical signal and counting the electrical signal.
12. The signal state and decoy state average photon number online detection method of claim 11, wherein the signal state and decoy state are converted into electrical signals by means of an optoelectronic probe and/or the electrical signals are counted by means of a counting function of an oscilloscope or by setting a magnitude counting threshold.
13. The on-line detection method of the average photon number of the signal state and the decoy state according to claim 10, wherein the single pulse intensity ratio sd of the signal state and the decoy state is obtained from the amplitude ratio of the electric signal by converting the signal state and the decoy state into the electric signal.
14. The on-line detection method of signal state and decoy state average photon number as claimed in claim 13, wherein the signal state and the decoy state are converted into first and second electric signals by means of an optoelectronic probe, the first and second electric signals are detected and recorded in amplitude by means of an oscilloscope, and the single pulse intensity ratio sd of the signal state and the decoy state is obtained according to the amplitude ratio of the first and second electric signals.
15. The online detection method of average photon numbers in signal states and decoy states according to claim 14, wherein the attenuation value L1 when the amplitude of the display of the oscillograph with respect to the decoy state is consistent with the recorded first electric signal amplitude is obtained by adjusting the attenuation value of the adjustable optical attenuator arranged in front of the photoelectric probe, the attenuation value L2 when the amplitude of the display of the oscillograph with respect to the signal state is consistent with the recorded second electric signal amplitude is obtained, and the monopulse intensity ratio sd of the signal state and the decoy state is calculated according to the absolute difference dL between the attenuation values L1 and L2.
16. The method for online detection of average photon numbers in signal states and in decoy states according to any one of claims 10 to 15, wherein when the total power P work of the output light is obtained, the method further comprises a step of demultiplexing and/or splitting the light pulse output by the transmitting end of the quantum key distribution device.
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