Quantum-inspired imaging techniques have been proven to be effective for LiDAR with the advances of single photon detectors and computational algorithms.However,due to the disturbance of background noise and the varie...Quantum-inspired imaging techniques have been proven to be effective for LiDAR with the advances of single photon detectors and computational algorithms.However,due to the disturbance of background noise and the varies of signal in outdoor environment,the performance of LiDAR is still far from its ultimate limit set by the quantum fluctuations of coherent probe light.In this work,we propose and demonstrate a LiDAR from the detection perspective for approaching the standard quantum-limited performance.The photon numbers of echo signals are recorded by a photon-number-resolving detector and applied to overcome heavy background noise through an active photon number filter in the LiDAR.It can approach the standard quantum limit in intensity estimation in a wide photon-flux range,and achieve a Fisher information of only 0.04 dB less than the quantum Fisher information when the mean signal photon number is 10.Experimentally,a noise-free target reconstruction and imaging is demonstrated in the daytime by the proposed LiDAR.It also performs better in reflectivity resolution when taking only 1/1000 of the measurements based on on/off detection.This work provides a fundamental strategy for constructing a LiDAR to quickly extract targets and identify materials in complex environments,which is important for intelligent agents such as autonomous vehicles.展开更多
Quantum computing is seeking to realize hardware-optimized algorithms for application-related computational tasks.NP(nondeterministic-polynomial-time)is a complexity class containing many important but intractable pro...Quantum computing is seeking to realize hardware-optimized algorithms for application-related computational tasks.NP(nondeterministic-polynomial-time)is a complexity class containing many important but intractable problems like the satisfiability of potentially conflict constraints(SAT).According to the well-founded exponential time hypothesis,verifying an SAT instance of size n requires generally the complete solution in an O(n)-bit proof.In contrast,quantum verification algorithms,which encode the solution into quantum bits rather than classical bit strings,can perform the verification task with quadratically reduced information about the solution in O~(Õ−−√n)qubits.Here we realize the quantum verification machine of SAT with single photons and linear optics.By using tunable optical setups,we efficiently verify satisfiable and unsatisfiable SAT instances and achieve a clear completeness-soundness gap even in the presence of experimental imperfections.The protocol requires only unentangled photons,linear operations on multiple modes and at most two-photon joint measurements.These features make the protocol suitable for photonic realization and scalable to large problem sizes with the advances in high-dimensional quantum information manipulation and large scale linear-optical systems.Our results open an essentially new route toward quantum advantages and extend the computational capability of optical quantum computing.展开更多
Quantum stochastic phase estimation has many applications in the precise measurement of various physical parameters.Similar to the estimation of a constant phase,there is a standard quantum limit for stochastic phase ...Quantum stochastic phase estimation has many applications in the precise measurement of various physical parameters.Similar to the estimation of a constant phase,there is a standard quantum limit for stochastic phase estimation,which can be obtained with the Mach-Zehnder interferometer and coherent input state.Recently,it has been shown that the stochastic standard quantum limit can be surpassed with nonclassical resources such as squcezed light.However,practical methods to achieve quantum enhancement in the stochastic phase estimation remain largely unexplored.Here we propose a method utilizing the SU(1,1)interferometer and coherent input states to cstimate a stochastic optical phase.As an example,we investigate the Ornstcin-Uhlenback stochastic phase.We analyze the performance of this method for three key estimation problems:prediction,tracking,and smoothing.The results show significant reduction of the mean square error compared with the Mach-Zehnder interferometer under the same photon number flux inside the interferometers.In particular,we show that the method with the SU(1,1)interferometer can achieve fundamental quantum scaling,achieve stochastic Heisenberg scalinga and surpass the precision of the canonical measurement.展开更多
Discriminating two spatially separated sources is one of the most fundamental problems in imaging.Recent research based on quantum parameter estimation theory shows that the resolution limit of two incoherent point so...Discriminating two spatially separated sources is one of the most fundamental problems in imaging.Recent research based on quantum parameter estimation theory shows that the resolution limit of two incoherent point sources given by Rayleigh can be broken.However,in realistic optical systems,there often exists coherence in the imaging light field,and there have been efforts to analyze the optical resolution in the presence of partial coherence.Nevertheless,how the degree of coherence between two point sources affects the resolution has not been fully understood.Here,we analyze the quantum-limited resolution of two partially coherent point sources by explicitly relating the state after evolution through the optical systems to the coherence of the sources.In particular,we consider the situation in which coherence varies with the separation.We propose a feasible experiment scheme to realize the nearly optimal measurement,which adaptively chooses the binary spatial-mode demultiplexing measurement and direct imaging.Our results will have wide applications in imaging involving coherence of light.展开更多
Laser communication using photons should consider not only the transmission environment’s effects,but also the performance of the single-photon detector used and the photon number distribution.Photon communication ba...Laser communication using photons should consider not only the transmission environment’s effects,but also the performance of the single-photon detector used and the photon number distribution.Photon communication based on the superconducting nanowire single-photon detector(SNSPD)is a new technology that addresses the current sensitivity limitations at the level of single photons in deep space communication.The communication’s bit error rate(BER)is limited by dark noise in the space environment and the photon number distribution with a traditional single-pixel SNSPD,which is unable to resolve the photon number distribution.In this work,an enhanced photon communication method was proposed based on the photon number resolving function of four-pixel array SNSPDs.A simulated picture transmission was carried out,and the error rate in this counting mode can be reduced by 2 orders of magnitude when compared with classical optical communication.However,in the communication mode using photon-enhanced counting,the four-pixel response amplitude for counting was found to restrain the communication rate,and this counting mode is extremely dependent on the incident light intensity through experiments,which limits the sensitivity and speed of the SNSPD array’s performance advantage.Therefore,a BER theoretical calculation model for laser communication was presented using the Bayesian estimation algorithm in order to analyze the selection of counting methods for information acquisition under different light intensities and to make better use of the SNSPD array’s high sensitivity and speed and thus to obtain a lower BER.The counting method and theoretical model proposed in this work refer to array SNSPDs in the deep space field.展开更多
基金supported by Frontier Technologies R&D Program of Jiangsu(No.BF2024058)the National Key Research and Development Program of China(No.2023YFC2205802)+4 种基金the Key-Area Research and Development Program of Guangdong Province(2020B0303020001)National Natural Science Foundation of China(No.12461160276)the Innovation Program for Quantum Science and Technology(No.2021ZD0303401)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)the Jiangsu Provincial Key Laboratory of Advanced Manipulating Technique of Electromagnetic Waves.
文摘Quantum-inspired imaging techniques have been proven to be effective for LiDAR with the advances of single photon detectors and computational algorithms.However,due to the disturbance of background noise and the varies of signal in outdoor environment,the performance of LiDAR is still far from its ultimate limit set by the quantum fluctuations of coherent probe light.In this work,we propose and demonstrate a LiDAR from the detection perspective for approaching the standard quantum-limited performance.The photon numbers of echo signals are recorded by a photon-number-resolving detector and applied to overcome heavy background noise through an active photon number filter in the LiDAR.It can approach the standard quantum limit in intensity estimation in a wide photon-flux range,and achieve a Fisher information of only 0.04 dB less than the quantum Fisher information when the mean signal photon number is 10.Experimentally,a noise-free target reconstruction and imaging is demonstrated in the daytime by the proposed LiDAR.It also performs better in reflectivity resolution when taking only 1/1000 of the measurements based on on/off detection.This work provides a fundamental strategy for constructing a LiDAR to quickly extract targets and identify materials in complex environments,which is important for intelligent agents such as autonomous vehicles.
基金This work was supported by the National Key Research and Development Program of China(Grant Nos.2019YFA0308700,2017YFA0303703 and 2018YFB1003202)the National Natural Science Foundation of China(Grant Nos.61972191,11690032,61975077 and 91836303)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.020214380068)P.Y.acknowledges financial support by Anhui Initiative in Quantum Information Technologies(Grant No.AHY150100).
文摘Quantum computing is seeking to realize hardware-optimized algorithms for application-related computational tasks.NP(nondeterministic-polynomial-time)is a complexity class containing many important but intractable problems like the satisfiability of potentially conflict constraints(SAT).According to the well-founded exponential time hypothesis,verifying an SAT instance of size n requires generally the complete solution in an O(n)-bit proof.In contrast,quantum verification algorithms,which encode the solution into quantum bits rather than classical bit strings,can perform the verification task with quadratically reduced information about the solution in O~(Õ−−√n)qubits.Here we realize the quantum verification machine of SAT with single photons and linear optics.By using tunable optical setups,we efficiently verify satisfiable and unsatisfiable SAT instances and achieve a clear completeness-soundness gap even in the presence of experimental imperfections.The protocol requires only unentangled photons,linear operations on multiple modes and at most two-photon joint measurements.These features make the protocol suitable for photonic realization and scalable to large problem sizes with the advances in high-dimensional quantum information manipulation and large scale linear-optical systems.Our results open an essentially new route toward quantum advantages and extend the computational capability of optical quantum computing.
基金National Key Research and Development Program of China(2017YFA0303703,2019YFA0308704)National Natural Science Foundation of China(11664017,11590052,11574155,51490711,61973077,91436211,91836303)+3 种基金Fundamental Research Funds for the Central Universitics(No.020214380068)Natural Science Foundjarion of Shanghai(17ZR1442900)Nanjing Universiry Innovation and Creative Program for PhD candidatc(2016017)Basic Research Project of Shanghai Science and Technology Commission(20JC1416100).
文摘Quantum stochastic phase estimation has many applications in the precise measurement of various physical parameters.Similar to the estimation of a constant phase,there is a standard quantum limit for stochastic phase estimation,which can be obtained with the Mach-Zehnder interferometer and coherent input state.Recently,it has been shown that the stochastic standard quantum limit can be surpassed with nonclassical resources such as squcezed light.However,practical methods to achieve quantum enhancement in the stochastic phase estimation remain largely unexplored.Here we propose a method utilizing the SU(1,1)interferometer and coherent input states to cstimate a stochastic optical phase.As an example,we investigate the Ornstcin-Uhlenback stochastic phase.We analyze the performance of this method for three key estimation problems:prediction,tracking,and smoothing.The results show significant reduction of the mean square error compared with the Mach-Zehnder interferometer under the same photon number flux inside the interferometers.In particular,we show that the method with the SU(1,1)interferometer can achieve fundamental quantum scaling,achieve stochastic Heisenberg scalinga and surpass the precision of the canonical measurement.
基金supported by the National Key Research and Development Program of China(Nos.2018YFA0306202 and 2017YFA0303703)the National Natural Science Foundation of China(Nos.91836303,61975077,61490711,and 11690032)the Fundamental Research Funds for the Central Universities(No.020214380068)。
文摘Discriminating two spatially separated sources is one of the most fundamental problems in imaging.Recent research based on quantum parameter estimation theory shows that the resolution limit of two incoherent point sources given by Rayleigh can be broken.However,in realistic optical systems,there often exists coherence in the imaging light field,and there have been efforts to analyze the optical resolution in the presence of partial coherence.Nevertheless,how the degree of coherence between two point sources affects the resolution has not been fully understood.Here,we analyze the quantum-limited resolution of two partially coherent point sources by explicitly relating the state after evolution through the optical systems to the coherence of the sources.In particular,we consider the situation in which coherence varies with the separation.We propose a feasible experiment scheme to realize the nearly optimal measurement,which adaptively chooses the binary spatial-mode demultiplexing measurement and direct imaging.Our results will have wide applications in imaging involving coherence of light.
基金National Key Research and Development Program of China(2017YFA0304002)National Natural Science Foundation of China(61571217,61521001,61801206,11227904)+1 种基金Priority Academic Program Development of Jiangsu Higher Education InstitutionsNanjing University。
文摘Laser communication using photons should consider not only the transmission environment’s effects,but also the performance of the single-photon detector used and the photon number distribution.Photon communication based on the superconducting nanowire single-photon detector(SNSPD)is a new technology that addresses the current sensitivity limitations at the level of single photons in deep space communication.The communication’s bit error rate(BER)is limited by dark noise in the space environment and the photon number distribution with a traditional single-pixel SNSPD,which is unable to resolve the photon number distribution.In this work,an enhanced photon communication method was proposed based on the photon number resolving function of four-pixel array SNSPDs.A simulated picture transmission was carried out,and the error rate in this counting mode can be reduced by 2 orders of magnitude when compared with classical optical communication.However,in the communication mode using photon-enhanced counting,the four-pixel response amplitude for counting was found to restrain the communication rate,and this counting mode is extremely dependent on the incident light intensity through experiments,which limits the sensitivity and speed of the SNSPD array’s performance advantage.Therefore,a BER theoretical calculation model for laser communication was presented using the Bayesian estimation algorithm in order to analyze the selection of counting methods for information acquisition under different light intensities and to make better use of the SNSPD array’s high sensitivity and speed and thus to obtain a lower BER.The counting method and theoretical model proposed in this work refer to array SNSPDs in the deep space field.
