The large-photon-number quantum state is a fundamental but nonresolved request for practical quantum information applications.We propose an N-photon state generation scheme that is feasible and scalable,using lithium ...The large-photon-number quantum state is a fundamental but nonresolved request for practical quantum information applications.We propose an N-photon state generation scheme that is feasible and scalable,using lithium niobate on insulator circuits.Such a scheme is based on the integration of a common building block called photon-number doubling unit(PDU)for deterministic single-photon parametric downconversion and upconversion.The PDU relies on a 107-optical-quality-factor resonator and mW-level on-chip power,which is within the current fabrication and experimental limits.N-photon state generation schemes,with cluster and Greenberger–Horne–Zeilinger state as examples,are shown for different quantum tasks.展开更多
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
Accurately estimating the overlap between quantum states is a fundamental task in quantum information processing.While various strategies using distinct quantum measurements have been proposed for overlap estimation,t...Accurately estimating the overlap between quantum states is a fundamental task in quantum information processing.While various strategies using distinct quantum measurements have been proposed for overlap estimation,the lack of experimental benchmarks on estimation precision limits strategy selection in different situations.Here we compare the performance of four practical strategies for overlap estimation,including tomography-tomography,tomographyprojection,Schur collective measurement and optical swap test using photonic quantum systems.We encode the quantum states on the polarization and path degrees of freedom of single photons.The corresponding measurements are performed by photon detection on certain modes following single-photon mode transformation or two-photon interference.We further propose an adaptive strategy with optimized precision in full-range overlap estimation.Our results shed new light on extracting the parameter of interest from quantum systems,prompting the design of efficientquantum protocols.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
基金supported by the National Key R&D Program of China(No.2019YFA0705000)the Key R&D Program of Guangdong Province(No.2018B030329001)+4 种基金the Leading-edge Technology Program of Jiangsu Natural Science Foundation(No.BK20192001)the National Natural Science Foundation of China(Nos.51890861,11690033,and 11974178)the Excellent Research Program of Nanjing University(No.ZYJH002)the support of the National Postdoctoral Program for Innovative Talents(No.BX2021122)China Postdoctoral Science Foundation(No.2022M711570).
文摘The large-photon-number quantum state is a fundamental but nonresolved request for practical quantum information applications.We propose an N-photon state generation scheme that is feasible and scalable,using lithium niobate on insulator circuits.Such a scheme is based on the integration of a common building block called photon-number doubling unit(PDU)for deterministic single-photon parametric downconversion and upconversion.The PDU relies on a 107-optical-quality-factor resonator and mW-level on-chip power,which is within the current fabrication and experimental limits.N-photon state generation schemes,with cluster and Greenberger–Horne–Zeilinger state as examples,are shown for different quantum tasks.
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supported by National Natural Science Foundation of China(GrantsNo.U24A2017,No.12347104 and No.12461160276)the National Key Researchand Development Program of China(Grants No.2023YFC2205802)+1 种基金Natural Science Foundation of Jiangsu Province(Grants No.BK20243060 and No.BK20233001)in part by State Key Laboratory of Advanced Optical Communication Systems and Networks,China.
文摘Accurately estimating the overlap between quantum states is a fundamental task in quantum information processing.While various strategies using distinct quantum measurements have been proposed for overlap estimation,the lack of experimental benchmarks on estimation precision limits strategy selection in different situations.Here we compare the performance of four practical strategies for overlap estimation,including tomography-tomography,tomographyprojection,Schur collective measurement and optical swap test using photonic quantum systems.We encode the quantum states on the polarization and path degrees of freedom of single photons.The corresponding measurements are performed by photon detection on certain modes following single-photon mode transformation or two-photon interference.We further propose an adaptive strategy with optimized precision in full-range overlap estimation.Our results shed new light on extracting the parameter of interest from quantum systems,prompting the design of efficientquantum protocols.
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.
