Continuous-variable quantum secure direct communication(CVQSDC)with Gaussian modulation(GM)demands a considerable quantity of random numbers during the preparation process and encodes them separately on the quadrature...Continuous-variable quantum secure direct communication(CVQSDC)with Gaussian modulation(GM)demands a considerable quantity of random numbers during the preparation process and encodes them separately on the quadrature components of the quantum states.Hence,high-speed random number generators are required to satisfy this demand,which is difficult to implement in practical applications.CVQSDC with discrete modulation(DM),correspondingly,employs a finite number of quantum states to achieve encoding,which can circumvent the shortcomings of the GM scheme.Based on the advantages of DM,the issue of attaining the most optimal secrecy capacity and communication distance remains to be resolved.Here,we propose a CVQSDC protocol based on N-symbol amplitude phase shift keying(N-APSK),which exploits the Boltzmann-Maxwell distribution assisted probability shaping technique.In comparison with the uniform distribution,according to 32-APSK CVQSDC,the proposed scheme extends the communication distance by about 38%,while obtaining a higher secrecy capacity at the same communication distance.Furthermore,increasing the value of N will concurrently increase the quantity of rings in the constellation,thereby facilitating enhancements of communication distance.This work incorporates the modulation approaches prevalently employed in classical communication into the realm of quantum communication,attaining gratifying advancements in communication distance and secrecy capacity,and concurrently facilitating the integrated development of quantum communication and classical communication.展开更多
Cavity-enhanced single quantum dots(QDs)are the main approach towards ultra-high-performance solid-state quantum light sources for scalable photonic quantum technologies.Nevertheless,harnessing the Purcell effect requ...Cavity-enhanced single quantum dots(QDs)are the main approach towards ultra-high-performance solid-state quantum light sources for scalable photonic quantum technologies.Nevertheless,harnessing the Purcell effect requires precise spectral and spatial alignment of the QDs’emission with the cavity mode,which is challenging for most cavities.Here we have successfully integrated miniaturized Fabry-Perot microcavities with a piezoelectric actuator,and demonstrated a bright single-photon source derived from a deterministically coupled QD within this microcavity.Leveraging the cavity-membrane structures,we have achieved large spectral tunability via strain tuning.On resonance,a high Purcell factor of~9 is attained.The source delivers single photons with simultaneous high extraction efficiency of 0.58,high purity of 0.956(2)and high indistinguishability of 0.922(4).Together with its compact footprint,our scheme facilitates the scalable integration of indistinguishable quantum light sources on-chip,therefore removing a major barrier to the development of solid-state quantum information platforms based on QDs.展开更多
The inevitable decoherence of quantum states leaks information to the environments and reduces the practical performance of quantum-information protocols.Quantum purification of coherent states provides an easy-to-imp...The inevitable decoherence of quantum states leaks information to the environments and reduces the practical performance of quantum-information protocols.Quantum purification of coherent states provides an easy-to-implement approach to decouple from the environments utilizing the correlation of several copies.However,repeated transmission of quantum states reduces the randomness of the collectivity and generates security vulnerabilities.In this paper,we propose a modified purification scheme and apply it to the continuous-variable quantum secure direct communication(CV-QSDC)protocol based on coherent states.The designed purification scheme improves the security capacity of communication systems through the effective suppression of excess noises,accompanied by the maintenance of source-side stochasticity.We conduct a proof-of-principle experiment of the purification scheme in the CV-QSDC system.The appearance of transmitted quantum states in phase space and two-dimensional Gaussian distributions have high goodness of fit at two copies.The security capability of this system is improved by 43.6%as the excess noise is reduced to 0.58 times the original noise by purification.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62071381 and 62301430)Shaanxi Fundamental Science Research Project for Mathematics and Physics(Grant No.23JSY014)+1 种基金Scientific Research Plan Project of Shaanxi Education Department Natural Science Special Project(Grant No.23JK0680)Young Talent Fund of Xi’an Association for Science and Technology(Grant No.959202313011)。
文摘Continuous-variable quantum secure direct communication(CVQSDC)with Gaussian modulation(GM)demands a considerable quantity of random numbers during the preparation process and encodes them separately on the quadrature components of the quantum states.Hence,high-speed random number generators are required to satisfy this demand,which is difficult to implement in practical applications.CVQSDC with discrete modulation(DM),correspondingly,employs a finite number of quantum states to achieve encoding,which can circumvent the shortcomings of the GM scheme.Based on the advantages of DM,the issue of attaining the most optimal secrecy capacity and communication distance remains to be resolved.Here,we propose a CVQSDC protocol based on N-symbol amplitude phase shift keying(N-APSK),which exploits the Boltzmann-Maxwell distribution assisted probability shaping technique.In comparison with the uniform distribution,according to 32-APSK CVQSDC,the proposed scheme extends the communication distance by about 38%,while obtaining a higher secrecy capacity at the same communication distance.Furthermore,increasing the value of N will concurrently increase the quantity of rings in the constellation,thereby facilitating enhancements of communication distance.This work incorporates the modulation approaches prevalently employed in classical communication into the realm of quantum communication,attaining gratifying advancements in communication distance and secrecy capacity,and concurrently facilitating the integrated development of quantum communication and classical communication.
基金We acknowledge Jin Liu and Yu-Ming He for the valuable discussions.We are grateful for financial support from the Science and Technology Program of Guangzhou(202103030001)the Innovation Program for Quantum Science and Technology(2021ZD0301400,2021ZD0301605)+4 种基金the National Key R&D Program of Guang-dong Province(2020B0303020001)the National Natural Science Foundation of China(12074442,12074433,12174447)the Natural Science Foundation of Hunan Province(2021JJ20051)the science and technology innovation Program of Hunan Province(2021RC3084)the research program of national university of defense technology(ZK21-01,22-ZZCX-067).
文摘Cavity-enhanced single quantum dots(QDs)are the main approach towards ultra-high-performance solid-state quantum light sources for scalable photonic quantum technologies.Nevertheless,harnessing the Purcell effect requires precise spectral and spatial alignment of the QDs’emission with the cavity mode,which is challenging for most cavities.Here we have successfully integrated miniaturized Fabry-Perot microcavities with a piezoelectric actuator,and demonstrated a bright single-photon source derived from a deterministically coupled QD within this microcavity.Leveraging the cavity-membrane structures,we have achieved large spectral tunability via strain tuning.On resonance,a high Purcell factor of~9 is attained.The source delivers single photons with simultaneous high extraction efficiency of 0.58,high purity of 0.956(2)and high indistinguishability of 0.922(4).Together with its compact footprint,our scheme facilitates the scalable integration of indistinguishable quantum light sources on-chip,therefore removing a major barrier to the development of solid-state quantum information platforms based on QDs.
基金supported by the National Natural Science Foundation of China(Grant Nos.62071381,and 62301430)Shaanxi Fundamental Science Research Project for Mathematics and Physics(Grant No.23JSY014)+2 种基金the Scientific Research Plan Project of Shaanxi Education Department(Natural Science Special Project(Grant No.23JK0680))the Young Talent Fund of Xi'an Association for Science and Technology(Grant No.959202313011)the Graduate Science and Technology Innovation Project at Northwest University(Grant No.CX2024200)。
文摘The inevitable decoherence of quantum states leaks information to the environments and reduces the practical performance of quantum-information protocols.Quantum purification of coherent states provides an easy-to-implement approach to decouple from the environments utilizing the correlation of several copies.However,repeated transmission of quantum states reduces the randomness of the collectivity and generates security vulnerabilities.In this paper,we propose a modified purification scheme and apply it to the continuous-variable quantum secure direct communication(CV-QSDC)protocol based on coherent states.The designed purification scheme improves the security capacity of communication systems through the effective suppression of excess noises,accompanied by the maintenance of source-side stochasticity.We conduct a proof-of-principle experiment of the purification scheme in the CV-QSDC system.The appearance of transmitted quantum states in phase space and two-dimensional Gaussian distributions have high goodness of fit at two copies.The security capability of this system is improved by 43.6%as the excess noise is reduced to 0.58 times the original noise by purification.
