78 results about "Decoy state" patented technology

A quantum key distribution station having the capability of forming decoy signals randomly interspersed with quantum signals as part of a QKD system is disclosed. The QKD station includes a polarization-independent high-speed optical switch adapted for use as a variable optical attenuator. The high-speed optical switch has a first attenuation level that results in first outgoing optical signals in the form of quantum signals having a mean photon number μ_Q, and a second attenuation level that results in second outgoing optical signals as decoy signals having a mean photon number PD. The attenuation level is randomly set during QKD system operation so that the decoy signals are randomly interspersed with the quantum signals.

The invention discloses a method and a device for preparing a high-speed polarization encoding decoy state quantum light source. The device comprises a high-speed logic control chip, a decoy state light pulse driving module, a high-speed phase modulator driving module, a laser diode, a high-speed phase modulation polarization rotating module and an optical attenuator, wherein the decoy state light pulse driving module receives a control signal from the high-speed logic control chip, randomly modulates according to the proportion requirement of a decoy state quantum light source implementation scheme to generate a decoy state electric pulse signal of three impulse amplitudes and drives the laser diode to output decoy state light pulse of three light intensities; the decoy state light pulse signal passes through the high-speed phase modulation polarization rotating module, is randomly modulated to be in four polarization states such as linear polarization-based state and circular polarization-based state through the high-speed phase modulator and is attenuated to be in a single photon level through the optical attenuator. According to the device and the method, any one state in totally nine quantum states comprising three average photon number intensities and four polarization states can be generated through high-rate random modulation, the device is small in size, compact in structure and easy to integrate, and the safety level is effectively improved.

The invention provides a system and method for measuring device-independent quantum key distribution (QKD). The system comprises a first-party device, a second-party device and a third-party device which are connected through a transmission channel, wherein both the first-party device and the second-party device comprise a controller, a processor and multiple lasers; the multiple lasers are used for respectively preparing the signal states and decoy states corresponding to two eigenstates of the signal measurement base and decoying the two decoy states of the measurement base; the controller selects one of the two groups of measurement bases, selects the signal states or the decoy states prepared by the corresponding lasers according to the selected measurement bases, and sends the signal states or the decoy states to the third-party device; the processor implements key post-processing on the received measurement results to obtain a secure key; and the third-party device implements Bell-state measurement on the received quantum state and releases the measurement results. By adopting the system and method provided by the invention, the number of the adopted lasers can be reduced without decreasing the performance of a QKD system, and thus the cost of the device can be lowered, the complexity of the device can be reduced, and more space of the client device can be saved.

The invention discloses a method and a device for manufacturing external modulation high-speed decoy-state quantum light sources. The method includes enabling an ultra-short pulse laser device to emit linearly polarized light pulses with high repetition frequencies; transmitting the linearly polarized light pulses into a high-speed light intensity modulation module; randomly modulating light pulse signals with originally identical intensities to obtain light pulse signals with different light intensities; transmitting the light pulse signals in signal states and decoy states into a polarization state generating light path to randomly generate light in four polarization states; attenuating the light by a light attenuator and then outputting light in nine quantum states. The light in the nine quantum states can have three light intensities and four polarization states. The device comprises the ultra-short pulse laser device, the high-speed light intensity modulation module, the polarization state generating light path, a high-speed light phase modulation module, the light attenuator and a high-speed logic control chip. The method and the device have the advantages that the intensities of the light pulses are externally modulated, the modulated light pulses in the different quantum states are excellent in consistency, and accordingly the problem of security vulnerability due to inconsistency in the shapes, the amplitude and the pulse widths of existing light pulses which are internally modulated can be solved.

The invention discloses a measurement device independent quantum key distribution system and method based on a W state. The system comprises four quantum terminal units and one quantum terminal unit.Pulsed lasers of the four quantum terminal units transmit laser of a specified wavelength, the phase of [0, 2 phi] is randomly modulated by a phase modulator, horizontal, vertical, +45-degree or -45-degree polarization is randomly loaded by a polarization controller, a decoy state or a signal state is marked by a strength modulator, and finally, the laser is attenuated by an adjustable attenuatorto an average photon number theoretically calculated and optimized and then transmitted to a quantum relay unit. The quantum relay unit performs W state projection measurement on signals transmitted through a quantum channel; according to the response of a detector, the quantum relay unit publishes the measurement result, and two are randomly selected from the four quantum terminal units to publish quantum states; if the quantum states of the two are anti-dependent, the data is discarded; and if the quantum states of the two are dependent, the remaining two are bit-flipped to obtain a shared password. The system and the method for quantum key distribution using the W state have better adaptability to the environment, and are low in cost by adopting mature basic linear optical components.

The invention provides a passive decoy state quantum digital signature method, which is applied in a quantum digital signature system. In the key distribution phase of the quantum digital signature, the invention utilizes the parametric down conversion process to generate signal light and casual light, the signal light is sent to the receiving end, and the casual light is used for local detection.The local detection at the transmitting end comprises a beam splitter (BS) and two detectors (D1, D2), After passing through the beam splitter, the casual light triggers two detectors to generate four different response events. The four response events are recorded and utilized to construct a new passive decoy state method, which greatly increases the number of keys that can be used for signatureunder the given security conditions. The method realizes over 200 km passive decoy state quantum digital signatures using a single mode standard commercial optical fiber, and the final signature rateis higher than that of some previous QDS systems. The scheme of the invention applies the passive decoy state technology to a quantum digital signature system for the first time.

The present invention provides a quantum key distribution method based on a single photon multi-degree of freedom irrelevant to a measurement device. The method employs spaces and polarization singlephotons to perform coding on a polarization freedom and a space path freedom and sends the spaces and polarization single photons after coding to a third-party measurement device. The third-party measurement device is employed to perform hyper-entangled Bell state analysis to achieve complete distinguishing of 16 Bell states. Compared to a quantum key distribution protocol scheme irrelevant to anoriginal measurement device, the information is encoded on two degrees of freedom, and a non-linear optical condition is employed to perform complete distinguishing of the 16 Bell states so as to effectively utilize the safe keys and improve the channel capacity. Besides, in order to respond to the safety hole of photon number separation attack, a decoy state technology is used. The quantum key distribution method based on a single photon multi-degree of freedom irrelevant to a measurement device can greatly improve the utilization of the code forming rate and the safe keys and can ensure thereliability and the safety of the transmission process.

The invention discloses an asymmetry-based communication method of decoy-state quantum key distribution protocols. The asymmetry-based communication method comprises the following steps that: a receiver and a sender establish a communication channel; the sender randomly generates a digital sequence and codes the digital sequence under multi-intensity light; if the light is in a signal state, coding is carried out under same basis vectors; if the light is in a weak decoy state, coding is carried out under a first basis vector or a second basis vector in different probabilities respectively; the sender sends coding information to the receiver; the receiver measures the coding information under the first basis vector or the second basis vector in different probabilities respectively, so that a source code is generated; and a shared key is screened from the source code according to the coding basis vector and the light intensity selected by the sender and the measurement basis vector selected by the receiver. According to the asymmetry-based communication method provided in the embodiment of the invention, on the premise of ensuring the communication security, the security key generation rate is increased by asymmetrically selecting the basis vectors; and thus, the systematic complexity is reduced.

The invention provides a high-speed quantum secret key distribution system of phase modulation polarization coding. The high-speed quantum secret key distribution system of the phase modulation polarization coding comprises a transmitter FPGA chip, a clock signal, a laser, an intensity modulator, a first polarization beam splitter and so on; wherein the transmitter FPGA chip is used for generatingrandom numbers, recording the generated random numbers, and driving the intensity modulator and a phase modulator; the clock signal is used for realizing the clock consistency between the transmitterand the receiver; the laser is used as a light source; the intensity modulator is used for receiving the random number signals transmitted by the FPGA, generating different modulation intensity and forming a decoy state; and the first polarization beam splitter is used for performing beam splitting on laser pulses. The high-speed quantum secret key distribution system of the phase modulation polarization coding improves the traditional quantum communication sending end, and adopts a single laser source; therefore, the noise and jitter caused by the differences of each laser are reduced, the number of the devices of the sending end is reduced, the complexity degree of the optical path is simplified, the bit error rate caused by the clock jitter is reduced, the redundant optical path structure in the prior art is improved, the system is simplified, and the cost is saved.

The invention provides a quantum secret key distributing system and method. The quantum secret key distributing system comprises a sending end and a receiving end, wherein a quantum channel and a classical channel are formed between the sending end and the receiving end; the sending end comprises a laser device, a first quantum random number generator, a signal state and decoy state encoder, a phase modulator, a second quantum random number generator, a register, a first transceiver and a first quantum secret key generator; and the receiving end comprises a first beam splitter, a second beam splitter, a translation device, a third quantum random number generator, a first detector, a second detector, a second transceiver and a second quantum secret key generator. According to the quantum secret key distributing system, the requirements of the whole system for the number of signals can be reduced, the coding rate of the system can be increased, and the transmission distance of a quantumsecret key and the generation speed of the secret key can be increased.

The invention discloses a quantum key allocation system and method based on continuous light chopping. A transmitting end comprises a continuous light signal laser, a synchronous laser, a continuous light chopping strength modulator, a decoy state strength modulator, a phase modulator, a first adjustable attenuator, a second adjustable attenuator and a transmitting end wavelength division multiplexer. A receiving end comprises a receiving end wavelength division multiplexer, a synchronous detector, a polarization beam splitter, a polarization-maintaining beam splitter and single photon detector. Compared with the prior art, the system and the method have the advantages that the polarization beam splitter is increased at the receiving end to split signal light into two vertical polarization states; interference under the polarization states is finished through utilization of polarization-maintaining optical fibers; a better interference result is obtained; the system tedious degree is simplified; moreover, a continuous light chopping form is employed at the transmitting end to obtain two light pulses with the consistent polarization states; the production of an interference ring of the transmitting end is avoided; the system tedious degree is further simplified; and the production cost is reduced.

The invention relates to a passive decoy state modulation reference system independent quantum key distribution system and method, and belongs to the technical field of quantum cryptography. The system comprises a transmitting end Alice signal preparation device and a Bob signal receiving and measuring device, wherein the transmitting end Alice signal preparation device comprises two pulse lasers Laser1 and Laser2, a beam splitter BS, a coding module and a threshold single-photon detector D0. The method comprises the following steps: describing QKD system parameters, and calculating a probability distribution rule of an Alice output signal of the transmitting end to determine a decoy state marking condition; respectively inputting a signal state and a decoy state into a coding module for modulation, wherein the coding module randomly selects one of three groups of mutually unbiased bases and codes key information on two intrinsic quantum states of each group of bases, a random coding mode is adopted and the result is sent to a receiving end Bob for measurement, base pairing screening, error correction and confidential amplification. The capability of the system for resisting rotation of a reference system is improved, and the overall key distribution performance is improved.

The invention discloses an improved HD-QKD system which comprises a sending end and a receiving end which are matched. The sending end carries out basis vector modulation and decoy state modulation onlight pulses on the basis of a light injection and internal modulation mode to obtain encoded light pulse groups, and after being attenuated, the light pulse groups are sent to the receiving end; andafter carrying out beam splitting on the encoded light pulse groups from the sending end, the receiving end respectively utilizes a Z basis vector detection and an X basis vector detection module tocarry out detection, wherein the X basis vector detection module comprises an interference module with a faraday rotator mirror and single photon detectors corresponding encoding dimensions of the light pulses, and each single photon detector respectively detects a corresponding interference result. The invention solves a problem of phase randomness among the pulse groups in an existing device anda problem of polarization drifting of the existing device.

The present invention provides a single decoy state quantum digital signature method provided. In a key distribution stage, efficient parameter estimation and quantum digital signature can be carriedout only by modulating the light source intensity into two intensities, namely a signal state and a decoy state. According to the method, the requirement for preparing the vacuum state in a traditional multi-intensity decoy state quantum digital signature scheme is avoided, the difficulty of experiment implementation is lowered, and meanwhile consumption of random numbers is reduced. According tothe invention, a low-loss unequal-arm Mach-Zehnder interferometer and a real-time polarization compensation method are used to realize efficient key transmission and signature. The system provided bythe invention is simple to implement and stable in operation, and successfully realizes higher signature rate and farther transmission distance on the premise of meeting the safety requirements of non-repudiation, unforgeability and transferability of a quantum digital signature protocol compared with the previous work.

The invention discloses an improved passive decoy state QKD (quantum key distribution) system based on an attenuation laser light source. Two independent phase-randomized weak coherent light beams areused for interference on a beam splitter, and output of the beam splitter serves as signal light and idle light which are transmitted to a receiving end and used for local detection. An adjustable beam splitter VBS and two detectors are added at a local detection position of a transmitting end, four different response events are generated after the idle light passes the VBS, and the four different response events are recorded and used for estimating and processing signals received by the receiving end. The transmitting end can acquire four different response events only by the aid of an attenuation light source and a standard linear optical element, more decoy states can be acquired, a compact estimation method is used, and various parameters of a key extraction ratio formula are effectively estimated. The different response events of the transmitting end are classified, more input parameters are acquired, and post-processing of the receiving end is facilitated to increase key extraction ratio and transmission distance.

The invention discloses an RFID system bidirectional authentication method based on a decoy state quantum random key. The method comprises: step (1), an RFID reader is associated with an EPC information server and the EPC information server is started; step (2), the RFID reader receives information-state and decoy-state weak coherent light that is sent by the EPC information server in an equal probability mode, extracts a secret key, and sends the secret key to an RFID tag; step (3), the RFID reader receives tag information of RFID tag after encryption and forwards the information to the EPC information server for authentication; if authentication is done successfully, a next step is executed; and otherwise, authentication fails; and step (4), the RFID reader receives the tag information that is encrypted by the EPC information server and is stored into the EPC information server and forwards the information to the RFID tag for authentication; if the authentication is done successfully, the RFID system carried out bidirectional authentication successfully; and otherwise, the authentication fails.

The invention discloses an independent quantum key distribution system and method for multi-user measurement equipment. The system comprises a plurality of clients and an intermediate measuring unit;lasers of the plurality of clients emit pulse laser and a polarization modulator randomly loads the pulse laser into horizontal, vertical, +45 degrees and -45 degrees polarized light pulse; after thepulse laser is subjected to an intensity modulator, a decoy state component is added, and then an adjustable attenuator accurately attenuates the pulse laser into a weak coherent laser pulse with an average photon number of less than 1. The intermediate measuring unit measures signals transmitted by the plurality of clients via a quantum channel; different results are output according to the jointpolarized quantum state of all users, the intermediate measuring unit announces a measurement result, and the plurality of clients generate a key locally based on the measurement result. According tothe independent quantum key distribution system for the multi-user measurement equipment provided by the invention, multiple parties can generate the same key at the same time, and the expansion is easy; and the adopted structure is simple, the used components are mature, the operation is simple, and the transmission is stable.

The invention discloses an asymmetric double-field quantum key distribution method through wide-area coordination control and a system. The method comprises the following steps: acquiring at least twolegal users Alice and Bob; determining pulse intensities and random phases of Alice and Bob in a decoy window, and judging whether the pulse intensities and the random phases are effective response events or not; according to the pulse intensity and the random phase, modulating the signal pulse and the decoy state pulse into different intensities and issuing the intensities; according to the modulated result and when it is determined that the event is an effective response event, respectively obtaining the lower bound Y1L and the error rate e1 of the single photon counting rates of Alice andBob; and performing error correction and privacy amplification on the lower bound Y1L and the error rate e1 of the single photon counting rate, determining a key generation rate and a final key, and finishing distribution. The method has the advantages that compared with the mode that an asymmetric channel is converted into a symmetric channel and an original symmetric protocol is utilized, the secret key generation rate and the transmission distance are effectively increased.

The invention discloses an electro-optical intensity modulator closed-loop control system and method in a quantum key distribution system. The electro-optical intensity modulator closed-loop control system comprises a laser device, an electro-optical intensity modulator IM, a beam splitter, photoelectric conversion module, a lock-in amplifier module, a direct-current offset module, an A/D conversion module, a D/A conversion module, a bias voltage drive module and an FPGA main control module, wherein the laser device is connected with the electro-optical intensity modulator IM; the electro-optical intensity modulator IM is connected with the beam splitter; one end of the beam splitter is connected with the photoelectric conversion module; the photoelectric conversion module is connected with the lock-in amplifier; the lock-in amplifier is connected with the direct-current offset module; the direct-current offset module is connected with the A/D conversion module; and the A/D conversionmodule is connected with the FPGA main control module. In the invention, through the control scheme of an IM direct-current working point formed by the lock-in amplifier feed performing real-time feedback and self-calibration, the problem of security threat caused by a decoy state preparation module in a QKD system is solved.

The invention provides a quantum key distribution light source based on a spontaneous radiation light source. A pulse generator is used for driving a first intensity modulator, a second intensity modulator and a polarization modulator; the spontaneous radiation light source is used for outputting a continuous direct current optical signal; a polarization beam splitter is used for generating a linearly polarized direct current optical signal; a filter is used for performing spectral filtering on the linearly polarized direct current optical signal; the first intensity modulator is used for modulating an optical signal output by the filter and generating a narrow optical pulse signal; the second intensity modulator is used for modulating the narrow optical pulse signal generated by the firstintensity modulator and generating a signal state, a decoy state and a vacuum state which are required by quantum key distribution; the polarization modulator is used for modulating an optical signaloutput by the second intensity modulator and generating +, -, L and R polarization states which are required by the quantum key distribution; and an attenuator is used for performing energy attenuation on an optical signal output by the polarization modulator and then outputting the energy-attenuated optical signal.

The embodiment of the invention discloses a stable decoy state pulse intensity modulation method and an intensity modulator, and the method comprises the steps: under the condition that the intensity of the decoy state pulse output by the intensity modulator is a stable point, determining the number of channels of an intensity modulator, the beam splitting ratio of a beam splitter in each channel, the attenuation rate of an adjustable attenuator and the target input pulse intensity of the input intensity modulator; through the maximum decoy state pulse intensity,determining target direct current voltage intensity needing to be loaded by each first terminal; and under the condition that the first terminal loads the target direct-current voltage intensity and the input pulse intensity is the target input pulse intensity, determining radio-frequency signal amplitudes needing to be loaded by the second terminals corresponding to decoy state pulses with different intensities through a preset first formula; therefore, by means of the method, output of any decoy pulses of various intensities can be met, and the influence of voltage fluctuation on the intensity of the output decoy pulses is small.

The invention provides a decoy state MDI-QKD method and a decoy state MDI-QKD system based on phase post-selection. A light source end modulates a plurality of strong reference pulses and signal pulses. And the detection end measures the phase difference of the reference pulse pair, compensates the common phase difference of the signal pulse pair, carries out Bell state measurement, and publishes a measurement result. The light source ends reserve data under the measurement result of effective response, reserve corresponding data when the two light source ends select Z basis vectors, obtain a string of bits, publish signal pulse intensity under the condition that the two light source ends do not select the Z basis vectors and private phases for sending first decoy state pulses in X basis vectors, select signal pulse pairs meeting set conditions, and send the selected signal pulse pairs to the two light source ends; and estimating the phase flipping error rate of the single photon pair in the Z basis vector, and performing post-processing on the screened bit string based on the phase flipping error rate to obtain a final key. According to the method, the observation bit error rate under the X basis vector is closer to the bit error rate generated by a single photon state through a phase post-selection mode, and the observation bit error rate is enough true, so that the phase flipping bit error rate can be estimated more intensively, a higher key rate is obtained, and the security of a protocol is not influenced.