Reliable detection of weak phase signals under significant channel loss and complex noise environments is a crucial step for practical applications of optical integrated communication and sensing systems. In this lett...Reliable detection of weak phase signals under significant channel loss and complex noise environments is a crucial step for practical applications of optical integrated communication and sensing systems. In this letter, we propose and experimentally demonstrate an enhanced long-distance weak signal transmission method assisted by weak measurement. Performing heterodyne detection and light intensity compensation on two nearly symmetric post-selected paths, the method enables real-time estimation of a time-varying phase while maintaining robustness against technical noises proportional to light intensity or photon number, detector common-mode noise, and significant attenuation over long-distance transmission. Experimental results indicate a potential phase sensitivity at the level of 10-8rad even with a signal light intensity attenuation of 48.1 d B. Potentially, combining the adaptive adjustment strategy, the method may provide a viable solution in remote weak signal detection and extraction,thereby contributing to optical integrated communication and sensing.展开更多
The well-known multi-dimensional reconciliation is an effective method used in the continuous-variable quantum key distribution in the long-distance and the low signal-to-noise-ratio scenarios.The virtual channel empl...The well-known multi-dimensional reconciliation is an effective method used in the continuous-variable quantum key distribution in the long-distance and the low signal-to-noise-ratio scenarios.The virtual channel employed to exchange data is generally established by using a finite-dimensional rotation in the reconciliation procedure.In this paper,we found that the finite dimension of the multi-dimensional reconciliation inevitably leads to the mismatch of the signal-to-noise-ratio between the quantum channel and the virtual channel,which may be called the finite-dimension effect.Such an effect results in an overestimation on the secret key rate,and subsequently induces vital practical security loopholes.展开更多
Gaussian-modulated coherent state quantum key distribution is gradually moving towards practical application. Generally, the involved scheme is based on the binary random basis choice. To improve the performance and s...Gaussian-modulated coherent state quantum key distribution is gradually moving towards practical application. Generally, the involved scheme is based on the binary random basis choice. To improve the performance and security, we present a scheme based on a continuous random basis choice. The results show that our scheme obviously improves the performance, such as the secure communication distance. Our scheme avoids comparing the measurement basis and discarding the key bits, and it can be easily implemented with current technology. Moreover, the imperfection of the basis choice can be well removed by the known phase compensation algorithm.展开更多
[Objectives]This study aimed to establish a method for simultaneous determination of four ingredients in Guanxin Danshen tablets by RP-HPLC.[Methods]HPLC chromatography was adopted with column of Thermo Hypersil-Keyst...[Objectives]This study aimed to establish a method for simultaneous determination of four ingredients in Guanxin Danshen tablets by RP-HPLC.[Methods]HPLC chromatography was adopted with column of Thermo Hypersil-Keystone C 18 column(4.6 mm×250 mm,5μm),mobile phase of acetonitrile(A)-0.03 mol/L ammonium acetate(pH adjusted to 2.4 with formic acid)(B),gradient elution(0-5 min,5%A;5-10 min,5%A→19%A;10-40 min,19%A;40-68 min,19%A→36%A;68-90 min,36%A→95%A),flow rate of 1.0 mL/min and column temperature of 25℃.[Results]The content of salvianic acid A sodium,protocatechuic aldehyde,salvianolic acid B and tanshinone II A showed good linear relationship with chromatographic peak area in the range of 3.310-18.66,0.03950-0.2370,0.7500-4.500,0.05920-0.3550μg,respectively.The recovery rate(n=6)was 101.75%,96.86%,104.15%and 99.03%,respectively,and the RSD was 1.52%,2.81%,1.80%,and 1.37%respectively.The established method has good precision,reproducibility and stability.[Conclusions]This method can be used for the quality control of multiple ingredients of Guanxin Danshen tablets.展开更多
The advent of quantum computers has significantly challenged the security of traditional cryptographic systems,prompting a surge in research on quantum key distribution(QKD).Among various QKD approaches,continuousvari...The advent of quantum computers has significantly challenged the security of traditional cryptographic systems,prompting a surge in research on quantum key distribution(QKD).Among various QKD approaches,continuousvariable QKD(CVQKD)offers superior resilience against background noise.However,the local local oscillator(LLO)CVQKD scheme faces substantial physical limitations in scenarios with high channel attenuation,and the large attenuation CVQKD remains unrealized.Bottleneck challenges include ensuring stable low-noise transmission and accurately estimating parameters under fluctuating channel conditions.We propose a continuousmode theoretical framework that provides an analytical method for time-varying quantum systems within a freespace channel.This framework can achieve high-fidelity LLO-CVQKD in free space without the need for complex,real-time frequency locking and transmittance calibration equipment.It can also enable free-space QKD under large attenuation and high repetition frequency.Through experimental validation,we first demonstrate high-rate secure quantum key distribution over high-loss free-space channels.Specifically,we achieve asymptotic key rates of 76.366 kbps and 403.896 kbps in 25 dB attenuation free-space channels without turbulence and 21.5 dB average attenuation free-space channels with turbulence,respectively.Additionally,we confirm the feasibility of experiments on mildly turbulent atmospheric channels spanning at least 10.5 km using current equipment.Our scheme provides direct insight into constructing an integrated air-ground quantum communication network.展开更多
The integration of sensing and communication can achieve ubiquitous sensing while enabling ubiquitous communication.Within the gradually improving global communication,the integrated sensing and communication system b...The integration of sensing and communication can achieve ubiquitous sensing while enabling ubiquitous communication.Within the gradually improving global communication,the integrated sensing and communication system based on optical fibers can accomplish various functionalities,such as urban structure imaging,seismic wave detection,and pipeline safety monitoring.With the development of quantum communication,quantum networks based on optical fiber are gradually being established.In this paper,we propose an integrated sensing and quantum network(ISAQN)scheme,which can achieve secure key distribution among multiple nodes and distributed sensing under the standard quantum limit.The continuous variables quantum key distribution protocol and the round-trip multiband structure are adopted to achieve the multinode secure key distribution.Meanwhile,the spectrum phase monitoring protocol is proposed to realize distributed sensing.It determines which node is vibrating by monitoring the frequency spectrum and restores the vibration waveform by monitoring the phase change.The scheme is experimentally demonstrated by simulating the vibration in a star structure network.Experimental results indicate that this multiuser quantum network can achieve a secret key rate of approximately 0.7 Mbits/s for each user under 10-km standard fiber transmission,and its network capacity is 8.In terms of distributed sensing,it can achieve a vibration response bandwidth ranging from 1 Hz to 2 kHz,a strain resolution of 0.50 nε/Hz,and a spatial resolution of 0.20 m under shot-noise-limited detection.The proposed ISAQN scheme enables simultaneous quantum communication and distributed sensing in a multipoint network,laying a foundation for future large-scale quantum networks and high-precision sensing networks.展开更多
Since the working conditions of classical and quantum signals are very different,how to effectively integrate classical and quantum communication networks without affecting their respective performance has become a gr...Since the working conditions of classical and quantum signals are very different,how to effectively integrate classical and quantum communication networks without affecting their respective performance has become a great challenge.In this paper,we proposed a scheme to realize classical communication and continuous-variable quantum key distribution(CV-QKD)based on frequency-division multiplexing(FDM),and we verified the feasibility of simultaneously realizing CV-QKD and classical optical communication data synchronous transmission scheme under the same infrastructure.We achieved a 0 bit error rate in 50 frames and a 20 Mb/s bit rate for the classical signal and an average secret key rate of around 5.86×105 bit/s for the quantum signal through a 4 dB fiber channel.This work provides a scheme to establish a QKD channel by only reserving a small passband in the entire optical communication instead of an entire wavelength,increasing efficiency and simplifying the integration of QKD and classical communication.展开更多
Quantum key distribution(QKD)has been proven to be theoretically unconditionally secure.However,any theoretical security proof relies on certain assumptions.In QKD,the assumption in the theoretical proof is that the s...Quantum key distribution(QKD)has been proven to be theoretically unconditionally secure.However,any theoretical security proof relies on certain assumptions.In QKD,the assumption in the theoretical proof is that the security of the protocol is considered under the asymptotic case where Alice and Bob exchange an infinite number of signals.In the continuous-variable QKD(CV-QKD),the finite-size effect imposes higher requirements on block size and excess noise control.However,the local local oscillator(LLO)CV-QKD system cannot be considered time-invariant under long blocks,especially in cases of environmental disturbances.Thus,we propose an LLO CV-QKD scheme with time-variant parameter estimation and compensation.We first establish an LLO CV-QKD theoretical model under the temporal modes of continuous-mode states.Then,a robust method is used to compensate for arbitrary frequency shift and arbitrary phase drift in CV-QKD systems with longer blocks,which cannot be achieved under traditional time-invariant parameter estimation.Besides,the digital signal processing method predicated on high-speed reference pilots can achieve a time complexity of O1.In the experiment,the frequency shift is up to 89.05 MHz/s and phase drift is up to 3.036 Mrad/s using a piezoelectric transducer(PZT)to simulate the turbulences in the practical channel.With a signal-to-interference ratio(SIR)of−51.67 dB,we achieve a secret key rate(SKR)of 0.29 Mbits/s with an attenuation of 16 dB or a standard fiber of 80 km.This work paves the way for future long-distance field-test experiments in the finite-size regime.展开更多
Quantum resources offer intrinsic randomness that is valuable for applications such as cryptography, scientific simulation, and computing. Silicon-based photonics chips present an excellent platform for the cost-effec...Quantum resources offer intrinsic randomness that is valuable for applications such as cryptography, scientific simulation, and computing. Silicon-based photonics chips present an excellent platform for the cost-effective deployment of next-generation quantum systems on a large scale, even at room temperature. Nevertheless,the potential susceptibility of these chips to hacker control poses a challenge in ensuring security for on-chip quantum random number generation, which is crucial for enabling extensive utilization of quantum resources.展开更多
The conventional Gaussian-modulated coherent-state quantum key distribution(QKD) protocol requires the sender to perform active modulations based on a true random number generator. Compared with it, the passive-state-...The conventional Gaussian-modulated coherent-state quantum key distribution(QKD) protocol requires the sender to perform active modulations based on a true random number generator. Compared with it, the passive-state-preparation(PSP) continuous-variable quantum key distribution(CVQKD) equivalently performs modulations passively by exploring the intrinsic field fluctuations of a thermal source, which offers the prospect of chip integration QKD with low cost. In this paper, we propose and experimentally demonstrate a high-rate PSP-CVQKD scheme within an access-network area using high-bandwidth detectors in a continuous wave encoding and decoding way. By proposing effective methods for suppressing the noises during the PSP process and polarization multiplexing to decrease the photon leakage noises, we realize the high-intensity local oscillator transmission, thereby achieving coherent detection with high efficiency, low noise, and high bandwidth. The secure key rates over transmission distance of 5.005 km with and without consideration of the finite-size effect are 273.25 Mbps and 1.09 Gbps. The use of the PSP method boosts the asymptotic secret key rate of CVQKD to Gbps level for the first time, to our knowledge, within the range of the access network, which provides an effective and secure key distribution strategy for high-speed quantum cryptography access communication.展开更多
The quantum network makes use of quantum states to transmit data,which will revolutionize classical communication and allow for some breakthrough applications.Quantum key distribution(QKD)is one prominent application ...The quantum network makes use of quantum states to transmit data,which will revolutionize classical communication and allow for some breakthrough applications.Quantum key distribution(QKD)is one prominent application of quantum networks,and can protect data transmission through quantum mechanics.In this work,we propose an expandable and cost-effective quantum access network,in which the round-trip structure makes quantum states travel in a circle to carry information,and the multi-band technique is proposed to support multiuser access.Based on the round-trip multi-band quantum access network,we realize multi-user secure key sharing through the continuous-variable QKD(CV-QKD)protocol.Due to the encoding characteristics of CV-QKD,the quadrature components in different frequency bands can be used to transmit key information for different users.The feasibility of this scheme is confirmed by comprehensive noise analysis,and is verified by a proof-of-principle experiment.The results show that each user can achieve excess noise suppression and 600 bit/s level secure key generation under 30 km standard fiber transmission.Such networks have the ability of multi-user access theoretically and could be expanded by plugging in simple modules.Therefore,it paves the way for near-term largescale quantum secure networks.展开更多
Integrated quantum key distribution(QKD)systems based on photonic chips have high scalability and stability,and are promising for further construction of global quantum communications networks.On-chip quantum light so...Integrated quantum key distribution(QKD)systems based on photonic chips have high scalability and stability,and are promising for further construction of global quantum communications networks.On-chip quantum light sources are a critical component of a fully integrated QKD system;especially a continuous-variable QKD(CVQKD)system based on coherent detection,which has extremely high requirements for the light sources.Here,for what we believe is the first time,we designed and fabricated two on-chip tunable lasers for CV-QKD,and demonstrated a high-performance system based on these sources.Because of the high output power,fine tunability,and narrow linewidth,the involved on-chip lasers guarantee the accurate shot-noise-limited detection of quantum signals,center wavelength alignment of nonhomologous lasers,and suppression of untrusted excess noise.The system’s secret key rate can reach 0.75 Mb/s at a 50 km fiber distance,and the secure transmission distance can exceed 100 km.Our results mark a breakthrough toward building a fully integrated CV-QKD,and pave the way for a reliable and efficient terrestrial quantum-secure metropolitan area network.展开更多
Exploring high sensitivity on the measurement of angular rotations is an outstanding challenge in optics and metrology.In this work,we employ the mn-order Hermite-Gaussian(HG) beam in the weak measurement scheme with ...Exploring high sensitivity on the measurement of angular rotations is an outstanding challenge in optics and metrology.In this work,we employ the mn-order Hermite-Gaussian(HG) beam in the weak measurement scheme with an angular rotation interaction,where the rotation information is taken by another HG mode state completely after the post-selection.By taking a projective measurement on the final light beam,the precision of angular rotation is improved by a factor of 2mn+m+n.For verification,we perform an optical experiment where the minimum detectable angular rotation improves √15-fold with HG55 mode over that of HG11 mode,and achieves a sub-microradian scale of the measurement precision.Our theoretical framework and experimental results not only provide a more practical and convenient scheme for ultrasensitive measurement of angular rotations but also contribute to a wide range of applications in quantum metrology.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.62471289)the Natural Science Foundation of Shanghai (Grant No.24ZR1432900)+1 种基金the Innovation Program for Quantum Science and Technology (Grant No.2021ZD0300703)Shanghai Municipal Science and Technology Major Project (Grant No.2019SHZDZX01)。
文摘Reliable detection of weak phase signals under significant channel loss and complex noise environments is a crucial step for practical applications of optical integrated communication and sensing systems. In this letter, we propose and experimentally demonstrate an enhanced long-distance weak signal transmission method assisted by weak measurement. Performing heterodyne detection and light intensity compensation on two nearly symmetric post-selected paths, the method enables real-time estimation of a time-varying phase while maintaining robustness against technical noises proportional to light intensity or photon number, detector common-mode noise, and significant attenuation over long-distance transmission. Experimental results indicate a potential phase sensitivity at the level of 10-8rad even with a signal light intensity attenuation of 48.1 d B. Potentially, combining the adaptive adjustment strategy, the method may provide a viable solution in remote weak signal detection and extraction,thereby contributing to optical integrated communication and sensing.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61332019,61671287,and 61631014)the National Key Research and Development Program of China(Grant No.2016YFA0302600)
文摘The well-known multi-dimensional reconciliation is an effective method used in the continuous-variable quantum key distribution in the long-distance and the low signal-to-noise-ratio scenarios.The virtual channel employed to exchange data is generally established by using a finite-dimensional rotation in the reconciliation procedure.In this paper,we found that the finite dimension of the multi-dimensional reconciliation inevitably leads to the mismatch of the signal-to-noise-ratio between the quantum channel and the virtual channel,which may be called the finite-dimension effect.Such an effect results in an overestimation on the secret key rate,and subsequently induces vital practical security loopholes.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61332019,61671287,and 61631014)Northwest University Doctorate Dissertation of Excellence Funds,China(Grant No.YYB17022)the National Key Research and Development Program,China(Grant No.2016YFA0302600)
文摘Gaussian-modulated coherent state quantum key distribution is gradually moving towards practical application. Generally, the involved scheme is based on the binary random basis choice. To improve the performance and security, we present a scheme based on a continuous random basis choice. The results show that our scheme obviously improves the performance, such as the secure communication distance. Our scheme avoids comparing the measurement basis and discarding the key bits, and it can be easily implemented with current technology. Moreover, the imperfection of the basis choice can be well removed by the known phase compensation algorithm.
基金Supported by Science and Technology Research Project of Jiangxi Provincial Department of Education(GJJ181381)
文摘[Objectives]This study aimed to establish a method for simultaneous determination of four ingredients in Guanxin Danshen tablets by RP-HPLC.[Methods]HPLC chromatography was adopted with column of Thermo Hypersil-Keystone C 18 column(4.6 mm×250 mm,5μm),mobile phase of acetonitrile(A)-0.03 mol/L ammonium acetate(pH adjusted to 2.4 with formic acid)(B),gradient elution(0-5 min,5%A;5-10 min,5%A→19%A;10-40 min,19%A;40-68 min,19%A→36%A;68-90 min,36%A→95%A),flow rate of 1.0 mL/min and column temperature of 25℃.[Results]The content of salvianic acid A sodium,protocatechuic aldehyde,salvianolic acid B and tanshinone II A showed good linear relationship with chromatographic peak area in the range of 3.310-18.66,0.03950-0.2370,0.7500-4.500,0.05920-0.3550μg,respectively.The recovery rate(n=6)was 101.75%,96.86%,104.15%and 99.03%,respectively,and the RSD was 1.52%,2.81%,1.80%,and 1.37%respectively.The established method has good precision,reproducibility and stability.[Conclusions]This method can be used for the quality control of multiple ingredients of Guanxin Danshen tablets.
基金Innovation Program for Quantum Science and Technology(2021ZD0300703)Shanghai Municipal Science and Technology Major Project(2019SHZDZX01)+1 种基金Key R&D Program of Guangdong Province(2020B0303040002)National Natural Science Foundation of China(62101320)。
文摘The advent of quantum computers has significantly challenged the security of traditional cryptographic systems,prompting a surge in research on quantum key distribution(QKD).Among various QKD approaches,continuousvariable QKD(CVQKD)offers superior resilience against background noise.However,the local local oscillator(LLO)CVQKD scheme faces substantial physical limitations in scenarios with high channel attenuation,and the large attenuation CVQKD remains unrealized.Bottleneck challenges include ensuring stable low-noise transmission and accurately estimating parameters under fluctuating channel conditions.We propose a continuousmode theoretical framework that provides an analytical method for time-varying quantum systems within a freespace channel.This framework can achieve high-fidelity LLO-CVQKD in free space without the need for complex,real-time frequency locking and transmittance calibration equipment.It can also enable free-space QKD under large attenuation and high repetition frequency.Through experimental validation,we first demonstrate high-rate secure quantum key distribution over high-loss free-space channels.Specifically,we achieve asymptotic key rates of 76.366 kbps and 403.896 kbps in 25 dB attenuation free-space channels without turbulence and 21.5 dB average attenuation free-space channels with turbulence,respectively.Additionally,we confirm the feasibility of experiments on mildly turbulent atmospheric channels spanning at least 10.5 km using current equipment.Our scheme provides direct insight into constructing an integrated air-ground quantum communication network.
基金supported by Innovation Program for Quantum Science and Technology(Grant No.2021ZD0300703)the National Natural Science Foundation of China(Grant No.62101320)+1 种基金the Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)the Hebei Provincial Science and Technology Project(Grant No.22310701D).
文摘The integration of sensing and communication can achieve ubiquitous sensing while enabling ubiquitous communication.Within the gradually improving global communication,the integrated sensing and communication system based on optical fibers can accomplish various functionalities,such as urban structure imaging,seismic wave detection,and pipeline safety monitoring.With the development of quantum communication,quantum networks based on optical fiber are gradually being established.In this paper,we propose an integrated sensing and quantum network(ISAQN)scheme,which can achieve secure key distribution among multiple nodes and distributed sensing under the standard quantum limit.The continuous variables quantum key distribution protocol and the round-trip multiband structure are adopted to achieve the multinode secure key distribution.Meanwhile,the spectrum phase monitoring protocol is proposed to realize distributed sensing.It determines which node is vibrating by monitoring the frequency spectrum and restores the vibration waveform by monitoring the phase change.The scheme is experimentally demonstrated by simulating the vibration in a star structure network.Experimental results indicate that this multiuser quantum network can achieve a secret key rate of approximately 0.7 Mbits/s for each user under 10-km standard fiber transmission,and its network capacity is 8.In terms of distributed sensing,it can achieve a vibration response bandwidth ranging from 1 Hz to 2 kHz,a strain resolution of 0.50 nε/Hz,and a spatial resolution of 0.20 m under shot-noise-limited detection.The proposed ISAQN scheme enables simultaneous quantum communication and distributed sensing in a multipoint network,laying a foundation for future large-scale quantum networks and high-precision sensing networks.
基金supported by the National Natural Science Foundation of China(Nos.62101320 and 61971276)the Innovation Program for Quantum Science and Technology(No.2021ZD0300703)+1 种基金the Shanghai Municipal Science and Technology Major Project(No.2019SHZDZX01)the Key R&D Program of Guangdong Province(No.2020B030304002).
文摘Since the working conditions of classical and quantum signals are very different,how to effectively integrate classical and quantum communication networks without affecting their respective performance has become a great challenge.In this paper,we proposed a scheme to realize classical communication and continuous-variable quantum key distribution(CV-QKD)based on frequency-division multiplexing(FDM),and we verified the feasibility of simultaneously realizing CV-QKD and classical optical communication data synchronous transmission scheme under the same infrastructure.We achieved a 0 bit error rate in 50 frames and a 20 Mb/s bit rate for the classical signal and an average secret key rate of around 5.86×105 bit/s for the quantum signal through a 4 dB fiber channel.This work provides a scheme to establish a QKD channel by only reserving a small passband in the entire optical communication instead of an entire wavelength,increasing efficiency and simplifying the integration of QKD and classical communication.
基金Innovation Program for Quantum Science and Technology(2021ZD0300703)National Natural Science Foundation of China(62101320)+1 种基金Shanghai Municipal Science and Technology Major Project(2019SHZDZX01)Hebei Provincial Science and Technology Project(22310701D)。
文摘Quantum key distribution(QKD)has been proven to be theoretically unconditionally secure.However,any theoretical security proof relies on certain assumptions.In QKD,the assumption in the theoretical proof is that the security of the protocol is considered under the asymptotic case where Alice and Bob exchange an infinite number of signals.In the continuous-variable QKD(CV-QKD),the finite-size effect imposes higher requirements on block size and excess noise control.However,the local local oscillator(LLO)CV-QKD system cannot be considered time-invariant under long blocks,especially in cases of environmental disturbances.Thus,we propose an LLO CV-QKD scheme with time-variant parameter estimation and compensation.We first establish an LLO CV-QKD theoretical model under the temporal modes of continuous-mode states.Then,a robust method is used to compensate for arbitrary frequency shift and arbitrary phase drift in CV-QKD systems with longer blocks,which cannot be achieved under traditional time-invariant parameter estimation.Besides,the digital signal processing method predicated on high-speed reference pilots can achieve a time complexity of O1.In the experiment,the frequency shift is up to 89.05 MHz/s and phase drift is up to 3.036 Mrad/s using a piezoelectric transducer(PZT)to simulate the turbulences in the practical channel.With a signal-to-interference ratio(SIR)of−51.67 dB,we achieve a secret key rate(SKR)of 0.29 Mbits/s with an attenuation of 16 dB or a standard fiber of 80 km.This work paves the way for future long-distance field-test experiments in the finite-size regime.
基金Key RD Program of Guangdong Province(2020B030304002)Shanghai Municipal Science and Technology Major Project (2019SHZDZX01)+1 种基金National Natural Science Foundation of China (61971276, 62101320)Innovation Program for Quantum Science and Technology(2021ZD0300703)。
文摘Quantum resources offer intrinsic randomness that is valuable for applications such as cryptography, scientific simulation, and computing. Silicon-based photonics chips present an excellent platform for the cost-effective deployment of next-generation quantum systems on a large scale, even at room temperature. Nevertheless,the potential susceptibility of these chips to hacker control poses a challenge in ensuring security for on-chip quantum random number generation, which is crucial for enabling extensive utilization of quantum resources.
基金National Natural Science Foundation of China(61971276, 62101320)Innovation Program for Quantum Science and Technology (2021ZD0300703)+1 种基金Shanghai Municipal Science and Technology Major Project(2019SHZDZX01)Key R&D Program of Guangdong Province (2020B030304002)。
文摘The conventional Gaussian-modulated coherent-state quantum key distribution(QKD) protocol requires the sender to perform active modulations based on a true random number generator. Compared with it, the passive-state-preparation(PSP) continuous-variable quantum key distribution(CVQKD) equivalently performs modulations passively by exploring the intrinsic field fluctuations of a thermal source, which offers the prospect of chip integration QKD with low cost. In this paper, we propose and experimentally demonstrate a high-rate PSP-CVQKD scheme within an access-network area using high-bandwidth detectors in a continuous wave encoding and decoding way. By proposing effective methods for suppressing the noises during the PSP process and polarization multiplexing to decrease the photon leakage noises, we realize the high-intensity local oscillator transmission, thereby achieving coherent detection with high efficiency, low noise, and high bandwidth. The secure key rates over transmission distance of 5.005 km with and without consideration of the finite-size effect are 273.25 Mbps and 1.09 Gbps. The use of the PSP method boosts the asymptotic secret key rate of CVQKD to Gbps level for the first time, to our knowledge, within the range of the access network, which provides an effective and secure key distribution strategy for high-speed quantum cryptography access communication.
基金Key R&D Program of Guangdong Province(2020B030304002)Shanghai Municipal Science and Technology Major Project(2019SHZDZX01)+1 种基金National Natural Science Foundation of China(61671287,61971276,62101320)National Key Research and Development Program of China(2016YFA0302600)。
文摘The quantum network makes use of quantum states to transmit data,which will revolutionize classical communication and allow for some breakthrough applications.Quantum key distribution(QKD)is one prominent application of quantum networks,and can protect data transmission through quantum mechanics.In this work,we propose an expandable and cost-effective quantum access network,in which the round-trip structure makes quantum states travel in a circle to carry information,and the multi-band technique is proposed to support multiuser access.Based on the round-trip multi-band quantum access network,we realize multi-user secure key sharing through the continuous-variable QKD(CV-QKD)protocol.Due to the encoding characteristics of CV-QKD,the quadrature components in different frequency bands can be used to transmit key information for different users.The feasibility of this scheme is confirmed by comprehensive noise analysis,and is verified by a proof-of-principle experiment.The results show that each user can achieve excess noise suppression and 600 bit/s level secure key generation under 30 km standard fiber transmission.Such networks have the ability of multi-user access theoretically and could be expanded by plugging in simple modules.Therefore,it paves the way for near-term largescale quantum secure networks.
基金Special Project for Research and Development in Key areas of Guangdong Province(2020B030304002)Shanghai Municipal Science and Technology Major Project(2019SHZDZX01)+1 种基金National Natural Science Foundation of China(61671287,61971276,62101320)National Key Research and Development Program of China(2016YFA0302600)。
文摘Integrated quantum key distribution(QKD)systems based on photonic chips have high scalability and stability,and are promising for further construction of global quantum communications networks.On-chip quantum light sources are a critical component of a fully integrated QKD system;especially a continuous-variable QKD(CVQKD)system based on coherent detection,which has extremely high requirements for the light sources.Here,for what we believe is the first time,we designed and fabricated two on-chip tunable lasers for CV-QKD,and demonstrated a high-performance system based on these sources.Because of the high output power,fine tunability,and narrow linewidth,the involved on-chip lasers guarantee the accurate shot-noise-limited detection of quantum signals,center wavelength alignment of nonhomologous lasers,and suppression of untrusted excess noise.The system’s secret key rate can reach 0.75 Mb/s at a 50 km fiber distance,and the secure transmission distance can exceed 100 km.Our results mark a breakthrough toward building a fully integrated CV-QKD,and pave the way for a reliable and efficient terrestrial quantum-secure metropolitan area network.
基金National Natural Science Foundation of China(61631014,61671287,61901258,62071298)State Key Laboratory of Advanced Optical Communication Systems and Networks。
文摘Exploring high sensitivity on the measurement of angular rotations is an outstanding challenge in optics and metrology.In this work,we employ the mn-order Hermite-Gaussian(HG) beam in the weak measurement scheme with an angular rotation interaction,where the rotation information is taken by another HG mode state completely after the post-selection.By taking a projective measurement on the final light beam,the precision of angular rotation is improved by a factor of 2mn+m+n.For verification,we perform an optical experiment where the minimum detectable angular rotation improves √15-fold with HG55 mode over that of HG11 mode,and achieves a sub-microradian scale of the measurement precision.Our theoretical framework and experimental results not only provide a more practical and convenient scheme for ultrasensitive measurement of angular rotations but also contribute to a wide range of applications in quantum metrology.
