Quantum key distribution(QKD)in principle can provide unconditional secure communication between distant parts.However,when finite-key length is taken into account,the security can only be ensured within certain secur...Quantum key distribution(QKD)in principle can provide unconditional secure communication between distant parts.However,when finite-key length is taken into account,the security can only be ensured within certain security level.In this paper,we adopt the Chernoff bound analysis method to deal with finite-key-size effects,carrying out corresponding investigations on the relationship between the key generation rate and security parameters for different protocols,including BB84,measurement-device-independent and twin-field QKD protocols.Simulation results show that there exists a fundamental limit between the key rate and the security parameters.Therefore,this study can provide valuable references for practical application of QKD,getting a nice balance between the key generation rate and the security level.展开更多
Quantum dialogue(QD)enables two communication parties to directly exchange secret messages simultaneously.In conventional QD protocols,photons need to transmit in the quantum channel for two rounds.In this paper,we pr...Quantum dialogue(QD)enables two communication parties to directly exchange secret messages simultaneously.In conventional QD protocols,photons need to transmit in the quantum channel for two rounds.In this paper,we propose a one-step QD protocol based on the hyperentanglement.With the help of the non-local hyperentanglement-assisted Bell state measurement(BSM),the photons only need to transmit in the quantum channel once.We prove that our one-step QD protocol is secure in theory and numerically simulate its secret message capacity under practical experimental condition.Compared with previous QD protocols,the one-step QD protocol can effectively simplify the experiment operations and reduce the message loss caused by the photon transmission loss.Meanwhile,the non-local hyperentanglement-assisted BSM has a success probability of 100%and is feasible with linear optical elements.Moreover,combined with the hyperentanglement heralded amplification and purification,our protocol is possible to realize long-distance one-step QD.展开更多
Encoding system plays a significant role in quantum key distribution(QKD).However,the security and performance of QKD systems can be compromised by encoding misalignment due to the inevitable defects in realistic devi...Encoding system plays a significant role in quantum key distribution(QKD).However,the security and performance of QKD systems can be compromised by encoding misalignment due to the inevitable defects in realistic devices.To alleviate the influence of misalignments,a method exploiting statistics from mismatched basis is proposed to enable uncharacterized sources to generate secure keys in QKD.In this work,we propose a scheme on four-intensity decoy-state quantum key distribution with uncharacterized heralded single-photon sources.It only requires the source states are prepared in a two-dimensional Hilbert space,and can thus reduce the complexity of practical realizations.Moreover,we carry out corresponding numerical simulations and demonstrate that our present four-intensity decoy-state scheme can achieve a much higher key rate compared than a three-intensity decoy-state method,and meantime it can obtain a longer transmission distance compared than the one using weak coherent sources.展开更多
The high-purity single-photon source plays an important role in the field of quantum information.Usually,it is generated through spontaneous parametric down-conversion process.In this paper,we investigate and summariz...The high-purity single-photon source plays an important role in the field of quantum information.Usually,it is generated through spontaneous parametric down-conversion process.In this paper,we investigate and summarize a few approaches on obtaining single-photon sources with a high purity using either PPKTP or PPLN nonlinear crystals.Moreover,we present improved schemes to increase the purity based on existing work,corresponding applicable conditions and procedures are discussed and analyzed.Besides,we carry out numerical simulations and show that nearly perfect purity can be reached even without using any filters.Therefore,this work might provide valuable references for the generation and application of high purity single-photon sources.展开更多
The hybrid entangled state is widely discussed in quantum information processing. In this paper, we propose the first protocol to directly measure the concurrence of the hybrid entangled state. To complete the measure...The hybrid entangled state is widely discussed in quantum information processing. In this paper, we propose the first protocol to directly measure the concurrence of the hybrid entangled state. To complete the measurement, we design parity check measurements(PCMs) for both the single polarization qubit and the coherent state. In this protocol, we perform three rounds of PCMs. The results show that we can convert the concurrence into the success probability of picking up the correct states from the initial entangled states. This protocol only uses polarization beam splitters, beam splitters, and weak cross-Kerr nonlinearities, which is feasible for future experiments. This protocol may be useful in future quantum information processing.展开更多
The one-step quantum secure direct communication(QSDC)(Sci.Bull.67,367(2022))can effectively simplify QSDC’s operation and reduce message loss.For enhancing its security under practical experimental condition,we prop...The one-step quantum secure direct communication(QSDC)(Sci.Bull.67,367(2022))can effectively simplify QSDC’s operation and reduce message loss.For enhancing its security under practical experimental condition,we propose two measurement-device-independent(MDI)one-step QSDC protocols,which can resist all possible attacks from imperfect measurement devices.In both protocols,the communication parties prepare identical polarization-spatial-mode two-photon hyperentangled states and construct the hyperentanglement channel by hyperentanglement swapping.The first MDI one-step QSDC protocol adopts the nonlinear-optical complete hyperentanglement Bell state measurement(HBSM)to construct the hyperentanglement channel,while the second protocol adopts the linear-optical partial HBSM.Then,the parties encode the photons in the polarization degree of freedom and send them to the third party for the hyperentanglementassisted complete polarization Bell state measurement.Both protocols are unconditionally secure in theory.The simulation results show the MDI one-step QSDC protocol with complete HBSM attains the maximal communication distance of about354 km.Our MDI one-step QSDC protocols may have potential applications in the future quantum secure communication field.展开更多
Quantum secret sharing(QSS) is a typical multi-party quantum communication mode, in which the key sender splits a key into several parts and the participants can obtain the key by cooperation. Measurement-device-indep...Quantum secret sharing(QSS) is a typical multi-party quantum communication mode, in which the key sender splits a key into several parts and the participants can obtain the key by cooperation. Measurement-device-independent quantum secret sharing(MDI-QSS) is immune to all possible attacks from measurement devices and can greatly enhance QSS's security in practical applications. However, previous MDI-QSS's key generation rate is relatively low. Here, we adopt the polarization-spatial-mode hyper-encoding technology in the MDI-QSS, which can increase single photon's channel capacity. Meanwhile, we use the cross-Kerr nonlinearity to realize the complete hyper-entangled Greenberger-Horne-Zeilinger state analysis. Both above factors can increase MDI-QSS's key generation rate by about 10^(3). The proposed hyper-encoded MDI-QSS protocol may be useful for future multiparity quantum communication applications.展开更多
We generalize BB84 quantum key distribution(QKD) to the scenario where the receiver adopts a heralded quantum memory(QM). With the heralded QM, the valid dark count rate of the receiver's single photon detectors c...We generalize BB84 quantum key distribution(QKD) to the scenario where the receiver adopts a heralded quantum memory(QM). With the heralded QM, the valid dark count rate of the receiver's single photon detectors can be mitigated obviously, which will lower the quantum bit error rate, and thus improve the performance of decoy-state BB84 QKD systems in long distance range. Simulation results show that, with practical experimental system parameters, decoy-state BB84 QKD with QM can exhibit performance comparable to that of without QM in short distance range, and exhibit performance better than that without QM in long distance range.展开更多
Reference-frame-independent quantum key distribution(RFI-QKD)has been proven to be very useful and practical under realistic environment.Here,we present a scheme for one-decoy state RFI-QKD based on the work of Rusca ...Reference-frame-independent quantum key distribution(RFI-QKD)has been proven to be very useful and practical under realistic environment.Here,we present a scheme for one-decoy state RFI-QKD based on the work of Rusca et al.[Appl.Phys.Lett.112,171104(2018)],and carry out investigation on its performance under realistic experimental conditions.Numerical simulation results show that the one-decoy state RFI-QKD can achieve comparable performance in terms of secret key rate and transmission distance as the two-decoy state correspondence under practical experimental conditions.On contrast,it does not need to prepare the vacuum state in the former case,substantially reducing the experimental complexity and random number consumptions.Therefore,our present proposal seems very promising in practical implementations of RFI-QKD.展开更多
Quantum correlation is a fundamental property that distinguishes quantum systems from classical ones,and is also a fragile resource under projective measurements.Recently,it has been shown that a subsystem in entangle...Quantum correlation is a fundamental property that distinguishes quantum systems from classical ones,and is also a fragile resource under projective measurements.Recently,it has been shown that a subsystem in entangled pairs can share nonlocalities with multiple observers in sequence.Here we present a new steering scenario where both subsystems are accessible by multiple observers.Simulation results show that the two qubits in a singlet state can be simultaneously steered separately by two sequential observers.展开更多
Quantum sensing,using quantum properties of sensors,can enhance resolution,precision,and sensitivity of imaging,spectroscopy,and detection.An intriguing question is:Can the quantum nature(quantumness)of sensors and ta...Quantum sensing,using quantum properties of sensors,can enhance resolution,precision,and sensitivity of imaging,spectroscopy,and detection.An intriguing question is:Can the quantum nature(quantumness)of sensors and targets be exploited to enable schemes that are not possible for classical probes or classical targets?Here we show that measurement of the quantum correlations of a quantum target indeed allows for sensing schemes that have no classical counterparts.As a concrete example,in the case that the second-order classical correlation of a quantum target could be totally concealed by non-stationary classical noise,the higher-order quantum correlations can single out a quantum target from the classical noise background,regardless of the spectrum,statistics,or intensity of the noise.Hence a classical-noise-free sensing scheme is proposed.This finding suggests that the quantumness of sensors and targets is still to be explored to realize the full potential of quantum sensing.New opportunities include sensitivity beyond classical approaches,non-classical correlations as a new approach to quantum many-body physics,loophole-free tests of the quantum foundation,et cetera.展开更多
As a fundamental tool in the quantum information field, quantum state tomography can be used to reconstruct any unknown state. Generally, it needs a tomographically complete set of measurements, such that all measurem...As a fundamental tool in the quantum information field, quantum state tomography can be used to reconstruct any unknown state. Generally, it needs a tomographically complete set of measurements, such that all measurements are fully characterized. Here, we propose a semi-measurement-device-independent quantum state tomography protocol, which only needs one characterized measurement and a trusted ancillary system. Furthermore, we perform corresponding experiments using linear optics. Our results show that the average state fidelity is as high as 0.973, verifying the effectiveness of the scheme.展开更多
Trapped atoms on photonic structures inspire many novel quantum devices for quantum information processing and quantum sensing.Here,we demonstrate a hybrid photonic-atom chip platform based on a Ga N-onsapphire chip a...Trapped atoms on photonic structures inspire many novel quantum devices for quantum information processing and quantum sensing.Here,we demonstrate a hybrid photonic-atom chip platform based on a Ga N-onsapphire chip and the transport of an ensemble of atoms from free space towards the chip with an optical conveyor belts.Due to our platform’s complete optical accessibility and careful control of atomic motion near the chip with a conveyor belt,successful atomic transport towards the chip is made possible.The maximum transport efficiency of atoms is about 50%with a transport distance of 500μm.Our results open up a new route toward the efficient loading of cold atoms into the evanescent-field trap formed by the photonic integrated circuits,which promises strong and controllable interactions between single atoms and single photons.展开更多
Measurement-device-independent quantum key distribution(MDI-QKD)provides us a powerful approach to resist all attacks at detection side.Besides the unconditional security,people also seek for high key generation rate,...Measurement-device-independent quantum key distribution(MDI-QKD)provides us a powerful approach to resist all attacks at detection side.Besides the unconditional security,people also seek for high key generation rate,but MDI-QKD has relatively low key generation rate.In this paper,we provide an efficient approach to increase the key generation rate of MDI-QKD by adopting multiple degrees of freedom(DOFs)of single photons to generate keys.Compared with other high-dimension MDI-QKD protocols encoding in one DOF,our protocol is more flexible,for our protocol generating keys in independent subsystems and the detection failure or error in a DOF not affecting the information encoding in other DOFs.Based on above features,our MDI-QKD protocol may have potential application in future quantum comniunication field.展开更多
Reference-frame-independent measurement-device-independent QKD(RFI-MDI-QKD), immune to both the slow unknown drift of reference frames and detector side channel attacks, can generate information-theoretic secure keys....Reference-frame-independent measurement-device-independent QKD(RFI-MDI-QKD), immune to both the slow unknown drift of reference frames and detector side channel attacks, can generate information-theoretic secure keys. Despite its natural resistance to the slow drift of reference frames, the performance of practical RFI-MDI-QKD systems descends with the increasing drift of reference frames. In this paper, we demonstrate the worst relative rotation of reference frames for practical RFI-MDI-QKD systems, and investigate their performance against the worst-case scenario,both of which are unclear to date. Simulation results show that, practical RFI-MDI-QKD systems can achieve quite good performance even against the worst-case scenario, which clearly demonstrates that it is possible to implement practical MDI-QKD systems with freely drifting reference frames.展开更多
In quantum key distribution(QKD),the passive decoy-state method can simplify the intensity modulation and reduce some of side-channel information leakage and modulation errors.It is usually implemented with a heralded...In quantum key distribution(QKD),the passive decoy-state method can simplify the intensity modulation and reduce some of side-channel information leakage and modulation errors.It is usually implemented with a heralded single-photon source.In Wang et al 2016(Phys.Rev.A 96032312),a novel passive decoy-state method is proposed by Wang et al,which uses two local detectors to generate more detection events for tightly estimating channel parameters.However,in the original scheme,the two local detectors are assumed to be identical,including the same detection efficiency and dark count rate,which is often not satisfied in the realistic experiment.In this paper,we construct a model for this passive decoy-state QKD scheme with two mismatched detectors and explore the effect on QKD performance with certain parameters.We also take the finite-size effect into consideration,showing the performance with statistical fluctuations.The results show that the efficiencies of local detectors affect the key rate more obviously than dark count rates.展开更多
Nonlocal correlations observed from entangled quantum particles imply the existence of intrinsic randomness.Normally, locally projective measurements performed on a two-qubit entangled state can only certify one-bit r...Nonlocal correlations observed from entangled quantum particles imply the existence of intrinsic randomness.Normally, locally projective measurements performed on a two-qubit entangled state can only certify one-bit randomness at most, while non-projective measurement can certify more randomness with the same quantum resources. In this Letter, we carry out an experimental investigation on quantum randomness certification through a symmetric informationally complete positive operator-valued measurement, which in principle can certify the maximum randomness through an entangled qubit. We observe the quantum nonlocal correlations that are close to the theoretical values. In the future, this work can provide a valuable reference for the research on the limit of randomness certification.展开更多
Quantum random access codes(QRACs) are important communication tasks that are usually implemented in prepare-andmeasure scenarios. The receiver tries to retrieve one arbitrarily chosen bit of the original bit-string f...Quantum random access codes(QRACs) are important communication tasks that are usually implemented in prepare-andmeasure scenarios. The receiver tries to retrieve one arbitrarily chosen bit of the original bit-string from the code qubit sent by the sender. In this Letter, we analyze in detail the sequential version of the 3 → 1 QRAC with two receivers. The average successful probability for the strategy of unsharp measurement is derived. The prepare-and-measure strategy within projective measurement is also discussed. It is found that sequential 3 → 1 QRAC with weak measurement cannot be always superior to the one with projective measurement, as the 2 → 1 version can be.展开更多
Hyperentanglement, the simultaneous entanglement in more than one degree of freedom(DOF), plays an important role in quantum communication and quantum information processing for it can effectively increase the channel...Hyperentanglement, the simultaneous entanglement in more than one degree of freedom(DOF), plays an important role in quantum communication and quantum information processing for it can effectively increase the channel capacity. Existing hyperentanglement sources mainly focus on the generation of the hyperentanglement in two DOFs. In this paper, we design the generation protocols for three kinds of hyperentanglement encoded in three DOFs with the practical coherent pulses sources, including the polarization-frequency-space hyperentanglement, the polarization-frequency-time-bin hyperentanglement, and the polarizationspace-time-bin hyperentanglement. These protocols exploit the spontaneous parametric down-conversion(SPDC) process and the Sagnac interferometer. The three protocols are all based on feasible experimental condition and may have potential applications in future hyperentanglement-based quantum communication and quantum information processing protocols.展开更多
Since its discovery,the quantum entanglement becomes a promising resource in quantum communication and computation.However,the entanglement is fragile due to the presence of noise in quantum channels.Entanglement puri...Since its discovery,the quantum entanglement becomes a promising resource in quantum communication and computation.However,the entanglement is fragile due to the presence of noise in quantum channels.Entanglement purification is a powerful tool to distill high quality entangled states from the low quality entangled states.In this review,we present an overview of entanglement purification,including the basic entanglement purification theory,the entanglement purification protocols(EPPs)with linear optics,EPPs with cross-Kerr nonlinearities,hyperentanglement EPPs,deterministic EPPs,and measurement-based EPPs.We also review experimental progress of EPPs in linear optics.Finally,we give the discussion on potential outlook for the future development of EPPs.This review may pave the way for practical implementations in future long-distance quantum communication and quantum network.展开更多
基金the Research on Key Technology and Equipment Development of Autonomous and Controllable Lightweight Endogenous Safety of Power Monitoring System(Grant No.5108-202118056A-0-0-00).
文摘Quantum key distribution(QKD)in principle can provide unconditional secure communication between distant parts.However,when finite-key length is taken into account,the security can only be ensured within certain security level.In this paper,we adopt the Chernoff bound analysis method to deal with finite-key-size effects,carrying out corresponding investigations on the relationship between the key generation rate and security parameters for different protocols,including BB84,measurement-device-independent and twin-field QKD protocols.Simulation results show that there exists a fundamental limit between the key rate and the security parameters.Therefore,this study can provide valuable references for practical application of QKD,getting a nice balance between the key generation rate and the security level.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12175106 and 92365110).
文摘Quantum dialogue(QD)enables two communication parties to directly exchange secret messages simultaneously.In conventional QD protocols,photons need to transmit in the quantum channel for two rounds.In this paper,we propose a one-step QD protocol based on the hyperentanglement.With the help of the non-local hyperentanglement-assisted Bell state measurement(BSM),the photons only need to transmit in the quantum channel once.We prove that our one-step QD protocol is secure in theory and numerically simulate its secret message capacity under practical experimental condition.Compared with previous QD protocols,the one-step QD protocol can effectively simplify the experiment operations and reduce the message loss caused by the photon transmission loss.Meanwhile,the non-local hyperentanglement-assisted BSM has a success probability of 100%and is feasible with linear optical elements.Moreover,combined with the hyperentanglement heralded amplification and purification,our protocol is possible to realize long-distance one-step QD.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12074194,12104240,and 62101285)the Industrial Prospect and Key Core Technology Projects of Jiangsu Provincial Key Research and Development Program(Grant No.BE2022071)the Natural Science Foundation of Jiangsu Province,China(Grant Nos.BK20192001 and BK20210582).
文摘Encoding system plays a significant role in quantum key distribution(QKD).However,the security and performance of QKD systems can be compromised by encoding misalignment due to the inevitable defects in realistic devices.To alleviate the influence of misalignments,a method exploiting statistics from mismatched basis is proposed to enable uncharacterized sources to generate secure keys in QKD.In this work,we propose a scheme on four-intensity decoy-state quantum key distribution with uncharacterized heralded single-photon sources.It only requires the source states are prepared in a two-dimensional Hilbert space,and can thus reduce the complexity of practical realizations.Moreover,we carry out corresponding numerical simulations and demonstrate that our present four-intensity decoy-state scheme can achieve a much higher key rate compared than a three-intensity decoy-state method,and meantime it can obtain a longer transmission distance compared than the one using weak coherent sources.
基金the National Key Research and Development Program of China(Grant Nos.2018YFA0306400 and 2017YFA0304100)the National Natural Science Foundation of China(Grant Nos.12074194,11774180,and U19A2075)the Leading-edge Technology Program of Jiangsu Natural Science Foundation,China(Grant No.BK20192001)。
文摘The high-purity single-photon source plays an important role in the field of quantum information.Usually,it is generated through spontaneous parametric down-conversion process.In this paper,we investigate and summarize a few approaches on obtaining single-photon sources with a high purity using either PPKTP or PPLN nonlinear crystals.Moreover,we present improved schemes to increase the purity based on existing work,corresponding applicable conditions and procedures are discussed and analyzed.Besides,we carry out numerical simulations and show that nearly perfect purity can be reached even without using any filters.Therefore,this work might provide valuable references for the generation and application of high purity single-photon sources.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11474168 and 11747161)a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘The hybrid entangled state is widely discussed in quantum information processing. In this paper, we propose the first protocol to directly measure the concurrence of the hybrid entangled state. To complete the measurement, we design parity check measurements(PCMs) for both the single polarization qubit and the coherent state. In this protocol, we perform three rounds of PCMs. The results show that we can convert the concurrence into the success probability of picking up the correct states from the initial entangled states. This protocol only uses polarization beam splitters, beam splitters, and weak cross-Kerr nonlinearities, which is feasible for future experiments. This protocol may be useful in future quantum information processing.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11974189 and 12175106)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Grant No.20KJB140001)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grand No.KYCX22-0963)
文摘The one-step quantum secure direct communication(QSDC)(Sci.Bull.67,367(2022))can effectively simplify QSDC’s operation and reduce message loss.For enhancing its security under practical experimental condition,we propose two measurement-device-independent(MDI)one-step QSDC protocols,which can resist all possible attacks from imperfect measurement devices.In both protocols,the communication parties prepare identical polarization-spatial-mode two-photon hyperentangled states and construct the hyperentanglement channel by hyperentanglement swapping.The first MDI one-step QSDC protocol adopts the nonlinear-optical complete hyperentanglement Bell state measurement(HBSM)to construct the hyperentanglement channel,while the second protocol adopts the linear-optical partial HBSM.Then,the parties encode the photons in the polarization degree of freedom and send them to the third party for the hyperentanglementassisted complete polarization Bell state measurement.Both protocols are unconditionally secure in theory.The simulation results show the MDI one-step QSDC protocol with complete HBSM attains the maximal communication distance of about354 km.Our MDI one-step QSDC protocols may have potential applications in the future quantum secure communication field.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11974189 and 12175106)。
文摘Quantum secret sharing(QSS) is a typical multi-party quantum communication mode, in which the key sender splits a key into several parts and the participants can obtain the key by cooperation. Measurement-device-independent quantum secret sharing(MDI-QSS) is immune to all possible attacks from measurement devices and can greatly enhance QSS's security in practical applications. However, previous MDI-QSS's key generation rate is relatively low. Here, we adopt the polarization-spatial-mode hyper-encoding technology in the MDI-QSS, which can increase single photon's channel capacity. Meanwhile, we use the cross-Kerr nonlinearity to realize the complete hyper-entangled Greenberger-Horne-Zeilinger state analysis. Both above factors can increase MDI-QSS's key generation rate by about 10^(3). The proposed hyper-encoded MDI-QSS protocol may be useful for future multiparity quantum communication applications.
基金supported by the National Key Research and Development Program of China (Grant Nos. 2018YFA0306400 and 2017YFA0304100)the National Natural Science Foundation of China (Grant Nos. 12074194 and 11774180)the Leading-edge Technology Program of Jiangsu Provincial Natural Science Foundation,China (Grant No. BK20192001)。
文摘We generalize BB84 quantum key distribution(QKD) to the scenario where the receiver adopts a heralded quantum memory(QM). With the heralded QM, the valid dark count rate of the receiver's single photon detectors can be mitigated obviously, which will lower the quantum bit error rate, and thus improve the performance of decoy-state BB84 QKD systems in long distance range. Simulation results show that, with practical experimental system parameters, decoy-state BB84 QKD with QM can exhibit performance comparable to that of without QM in short distance range, and exhibit performance better than that without QM in long distance range.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2018YFA0306400 and 2017YFA0304100)the National Natural Science Foundation of China(Grant Nos.61590932,11774180,and 61705110)the Natural Science Foundation of Jiangsu Province for Leading-edge Technology Program,China(Grant No.BK20192001).
文摘Reference-frame-independent quantum key distribution(RFI-QKD)has been proven to be very useful and practical under realistic environment.Here,we present a scheme for one-decoy state RFI-QKD based on the work of Rusca et al.[Appl.Phys.Lett.112,171104(2018)],and carry out investigation on its performance under realistic experimental conditions.Numerical simulation results show that the one-decoy state RFI-QKD can achieve comparable performance in terms of secret key rate and transmission distance as the two-decoy state correspondence under practical experimental conditions.On contrast,it does not need to prepare the vacuum state in the former case,substantially reducing the experimental complexity and random number consumptions.Therefore,our present proposal seems very promising in practical implementations of RFI-QKD.
基金the financial support from the National Key R&D Program of China(Grant Nos.2018YFA0306400 and 2017YFA0304100)the National Natural Science Foundation of China(Grant Nos.12074194 and U19A2075)+1 种基金Leading-Edge Technology Program of Jiangsu Natural Science Foundation(Grant No.BK20192001)the Industrial Prospect and Key Core Technology Projects of Jiangsu Provincial Key R&D Program(Grant No.BE2022071)。
文摘Quantum correlation is a fundamental property that distinguishes quantum systems from classical ones,and is also a fragile resource under projective measurements.Recently,it has been shown that a subsystem in entangled pairs can share nonlocalities with multiple observers in sequence.Here we present a new steering scenario where both subsystems are accessible by multiple observers.Simulation results show that the two qubits in a singlet state can be simultaneously steered separately by two sequential observers.
基金Supported by Hong Kong RGC/GRF Project(Grant No.14300119).
文摘Quantum sensing,using quantum properties of sensors,can enhance resolution,precision,and sensitivity of imaging,spectroscopy,and detection.An intriguing question is:Can the quantum nature(quantumness)of sensors and targets be exploited to enable schemes that are not possible for classical probes or classical targets?Here we show that measurement of the quantum correlations of a quantum target indeed allows for sensing schemes that have no classical counterparts.As a concrete example,in the case that the second-order classical correlation of a quantum target could be totally concealed by non-stationary classical noise,the higher-order quantum correlations can single out a quantum target from the classical noise background,regardless of the spectrum,statistics,or intensity of the noise.Hence a classical-noise-free sensing scheme is proposed.This finding suggests that the quantumness of sensors and targets is still to be explored to realize the full potential of quantum sensing.New opportunities include sensitivity beyond classical approaches,non-classical correlations as a new approach to quantum many-body physics,loophole-free tests of the quantum foundation,et cetera.
基金supported by the National Key Research and Development Program of China (Grant Nos. 2018YFA0306400 and 2017YFA0304100)the National Natural Science Foundation of China (Grant Nos. 12074194 and U19A2075)the Leading-Edge Technology Program of Jiangsu Natural Science Foundation (Grant No. BK20192001)。
文摘As a fundamental tool in the quantum information field, quantum state tomography can be used to reconstruct any unknown state. Generally, it needs a tomographically complete set of measurements, such that all measurements are fully characterized. Here, we propose a semi-measurement-device-independent quantum state tomography protocol, which only needs one characterized measurement and a trusted ancillary system. Furthermore, we perform corresponding experiments using linear optics. Our results show that the average state fidelity is as high as 0.973, verifying the effectiveness of the scheme.
基金supported by the National Key R&D Program(Grant No.2021YFF0603701)the National Natural Science Foundation of China(Grant Nos.U21A20433,U21A6006,92265210,12104441,12134014,61905234,and 11974335)+1 种基金the USTC Research Funds of the Double First-Class Initiative(Grant No.YD2030002007),USTC Research Funds of the Double First-Class Initiativesupported by the Fundamental Research Funds for the Central Universities。
文摘Trapped atoms on photonic structures inspire many novel quantum devices for quantum information processing and quantum sensing.Here,we demonstrate a hybrid photonic-atom chip platform based on a Ga N-onsapphire chip and the transport of an ensemble of atoms from free space towards the chip with an optical conveyor belts.Due to our platform’s complete optical accessibility and careful control of atomic motion near the chip with a conveyor belt,successful atomic transport towards the chip is made possible.The maximum transport efficiency of atoms is about 50%with a transport distance of 500μm.Our results open up a new route toward the efficient loading of cold atoms into the evanescent-field trap formed by the photonic integrated circuits,which promises strong and controllable interactions between single atoms and single photons.
基金supported by the National Natural Science Foundation of China under Grant Nos.11974189,12005106the Postgraduate Research&Practice Innovation Program of Jiangsu Province under Grant No.SJCX19-0241a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Measurement-device-independent quantum key distribution(MDI-QKD)provides us a powerful approach to resist all attacks at detection side.Besides the unconditional security,people also seek for high key generation rate,but MDI-QKD has relatively low key generation rate.In this paper,we provide an efficient approach to increase the key generation rate of MDI-QKD by adopting multiple degrees of freedom(DOFs)of single photons to generate keys.Compared with other high-dimension MDI-QKD protocols encoding in one DOF,our protocol is more flexible,for our protocol generating keys in independent subsystems and the detection failure or error in a DOF not affecting the information encoding in other DOFs.Based on above features,our MDI-QKD protocol may have potential application in future quantum comniunication field.
基金Supported by the National Key Research and Development Program of China under Grant Nos.2018YFA0306400 and 2017YFA0304100the National Natural Science Foundation of China under Grant Nos.61475197,61590932,11774180,and 61705110+3 种基金the Natural Science Foundation of the Jiangsu Higher Education Institutions under Grant Nos.15KJA120002 and 17KJB140016the Natural Science Foundation of Jiangsu Province under Grant No.BK20170902the Outstanding Youth Project of Jiangsu under Grant No.BK20150039the Postgraduate Research&Practice Innovation Program of Jiangsu Province under Grant No.KYCX18 0906
文摘Reference-frame-independent measurement-device-independent QKD(RFI-MDI-QKD), immune to both the slow unknown drift of reference frames and detector side channel attacks, can generate information-theoretic secure keys. Despite its natural resistance to the slow drift of reference frames, the performance of practical RFI-MDI-QKD systems descends with the increasing drift of reference frames. In this paper, we demonstrate the worst relative rotation of reference frames for practical RFI-MDI-QKD systems, and investigate their performance against the worst-case scenario,both of which are unclear to date. Simulation results show that, practical RFI-MDI-QKD systems can achieve quite good performance even against the worst-case scenario, which clearly demonstrates that it is possible to implement practical MDI-QKD systems with freely drifting reference frames.
基金We gratefully acknowledge the financial support from the National Key R&D Program of China(2018YFA0306400,2017YFA0304100)the National Natural Science Foundation of China(12074194,11774180,U19A2075,12104240,62101285)+2 种基金the Leading-edge technology Program of Jiangsu Natural Science Foundation(BK20192001)Natural Science Foundation of Jiangsu Province(BK20210582)NUPTSF(NY220122,NY220123).
文摘In quantum key distribution(QKD),the passive decoy-state method can simplify the intensity modulation and reduce some of side-channel information leakage and modulation errors.It is usually implemented with a heralded single-photon source.In Wang et al 2016(Phys.Rev.A 96032312),a novel passive decoy-state method is proposed by Wang et al,which uses two local detectors to generate more detection events for tightly estimating channel parameters.However,in the original scheme,the two local detectors are assumed to be identical,including the same detection efficiency and dark count rate,which is often not satisfied in the realistic experiment.In this paper,we construct a model for this passive decoy-state QKD scheme with two mismatched detectors and explore the effect on QKD performance with certain parameters.We also take the finite-size effect into consideration,showing the performance with statistical fluctuations.The results show that the efficiencies of local detectors affect the key rate more obviously than dark count rates.
基金financially supported by the National Key R&D Program of China (Nos. 2018YFA0306400 and 2017YFA0304100)the National Natural Science Foundation of China (Nos. 11774180 and 61590932)+1 种基金the Leading-edge Technology Program of Jiangsu Natural Science Foundation (No. BK20192001)the Postgraduate Research and Practice Innovation Program of Jiangsu Province (No. KYCX18_0915)
文摘Nonlocal correlations observed from entangled quantum particles imply the existence of intrinsic randomness.Normally, locally projective measurements performed on a two-qubit entangled state can only certify one-bit randomness at most, while non-projective measurement can certify more randomness with the same quantum resources. In this Letter, we carry out an experimental investigation on quantum randomness certification through a symmetric informationally complete positive operator-valued measurement, which in principle can certify the maximum randomness through an entangled qubit. We observe the quantum nonlocal correlations that are close to the theoretical values. In the future, this work can provide a valuable reference for the research on the limit of randomness certification.
基金This work was supported by the National Key Research and Development Program of China(Nos.2018YFA0306400 and 2017YFA0304100)the National Natural Science Foundation of China(Nos.12074194,11774180,and U19A2075)the Leading-Edge Technology Program of Jiangsu Natural Science Foundation(No.BK20192001)。
文摘Quantum random access codes(QRACs) are important communication tasks that are usually implemented in prepare-andmeasure scenarios. The receiver tries to retrieve one arbitrarily chosen bit of the original bit-string from the code qubit sent by the sender. In this Letter, we analyze in detail the sequential version of the 3 → 1 QRAC with two receivers. The average successful probability for the strategy of unsharp measurement is derived. The prepare-and-measure strategy within projective measurement is also discussed. It is found that sequential 3 → 1 QRAC with weak measurement cannot be always superior to the one with projective measurement, as the 2 → 1 version can be.
基金supported by the National Natural Science Foundation of China(Grant Nos.11974189,12175106,and 92365110)Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX23-1027)。
文摘Hyperentanglement, the simultaneous entanglement in more than one degree of freedom(DOF), plays an important role in quantum communication and quantum information processing for it can effectively increase the channel capacity. Existing hyperentanglement sources mainly focus on the generation of the hyperentanglement in two DOFs. In this paper, we design the generation protocols for three kinds of hyperentanglement encoded in three DOFs with the practical coherent pulses sources, including the polarization-frequency-space hyperentanglement, the polarization-frequency-time-bin hyperentanglement, and the polarizationspace-time-bin hyperentanglement. These protocols exploit the spontaneous parametric down-conversion(SPDC) process and the Sagnac interferometer. The three protocols are all based on feasible experimental condition and may have potential applications in future hyperentanglement-based quantum communication and quantum information processing protocols.
基金supported by the National Natural Science Foundation of China(Grant Nos.11974189,and 12175106)the Natural Science Foundation of Jiangsu Higher Education Institutions of China(Grant No.20KJB140001).
文摘Since its discovery,the quantum entanglement becomes a promising resource in quantum communication and computation.However,the entanglement is fragile due to the presence of noise in quantum channels.Entanglement purification is a powerful tool to distill high quality entangled states from the low quality entangled states.In this review,we present an overview of entanglement purification,including the basic entanglement purification theory,the entanglement purification protocols(EPPs)with linear optics,EPPs with cross-Kerr nonlinearities,hyperentanglement EPPs,deterministic EPPs,and measurement-based EPPs.We also review experimental progress of EPPs in linear optics.Finally,we give the discussion on potential outlook for the future development of EPPs.This review may pave the way for practical implementations in future long-distance quantum communication and quantum network.
