High-dimensional(HD)entanglement provides a very promising way of transcending the limitations of the twodimensional entanglement between qubits for increasing channel capacity in many quantum protocols.In the pursuit...High-dimensional(HD)entanglement provides a very promising way of transcending the limitations of the twodimensional entanglement between qubits for increasing channel capacity in many quantum protocols.In the pursuit of capitalizing on the HD entangled states,one of the central issues is to unambiguously and comprehensively quantilfy and reconstruct them.The full quantum state tomography is a unique solution,but it is undesirable and even impractical because the measurements increase rapidly in d^4 for a bipartite d-dimensional quantum state.Here we present a very efficient and practical tomography method—asymptotical locking tomography(ALT),which can harvest full information of bipartite d-dimensional entangled states by very few measurements less than 2 d^2 only.To showcase the validity and reasonableness of our ALT,we carry out the test with the two-photon spin-orbital angular momentum hyperentangled states in a four-dimensional subspace.Besides high-efficiency and practicality,our ALT is also universal and can be generalized into multipartite HD entanglement and other quantum systems.展开更多
Ghost imaging functions achieved by means of the spatial correlations between two photons is a new modality in imaging systems. With a small number of photons, ghost imaging is usually realized based on the position c...Ghost imaging functions achieved by means of the spatial correlations between two photons is a new modality in imaging systems. With a small number of photons, ghost imaging is usually realized based on the position correlation of photon pairs produced from the spontaneous parametric down-conversion process. Here we demonstrate a way to realize multi-path ghost imaging by introducing an additional time correlation. Different delays of paths will induce the shift of the coincidence peak, which carries the information about objects. By choosing the suitable coincidence window, we obtain images of three objects simultaneously, with a visibility of 87.2%.This method provides insights and techniques into multi-parameter ghost imaging. It can be applied to other correlated imaging systems, for example, quantum spiral imaging.展开更多
In recent years,orbital angular momentum(OAM),as a new usable degree of freedom of photons,has been widely applied in both classical optics and quantum optics.For example,digital spiral imaging uses the OAM spectrum o...In recent years,orbital angular momentum(OAM),as a new usable degree of freedom of photons,has been widely applied in both classical optics and quantum optics.For example,digital spiral imaging uses the OAM spectrum of the output beam from the object to restore the symmetry information of the object.However,the related experiments have been carried out in free space so far.Due to the poor anti-noise performance,limited transmission distance and other reasons,the practicability is seriously restricted.Here,we have carried out a digital spiral imaging experiment through a few-mode fiber,to achieve the identification of the symmetry of object by measuring the OAM spectrum of the output beam.In experiment,we have demonstrated the identification of the symmetry of amplitude-only and phase-only objects with the two-,three-and four-fold rotational symmetries.We also give the understanding of the physics.We believe that our work has greatly improved the practical application of digital spiral imaging in remote sensing.展开更多
We present a two-photon interference experiment in a modified Mach-Zehnder （MZ） interferometer in which two Hong-Ou-Mandel effects occur in tandem and construct superposed two-photon states. The signal photons pass ...We present a two-photon interference experiment in a modified Mach-Zehnder （MZ） interferometer in which two Hong-Ou-Mandel effects occur in tandem and construct superposed two-photon states. The signal photons pass both the arms of the MZ interferometer while the idler photons pass one arm only. Interestingly, the probability of the idler photons emerging from any output port still shows a sine oscillation with the two-photon phase difference and it can be characterized only by the indistinguishability of the two-photon amplitudes. We also observe a two-photon interference pattern with a period being equal to the wavelength of the parametric photons instead of the two-photon photonie de Broglie wavelength due to the presence of two-photon phase difference, in particular, with complementary probabilities of finding the two-photon pairs in two output ports. The abundant observations can facilitate a more comprehensive understanding of the two-photon interference.展开更多
Optical orbital angular momentum(OAM) is a special property of photons and has evoked research onto the light–matter interaction in both classical and quantum regimes. In classical optics, OAM is related to an optica...Optical orbital angular momentum(OAM) is a special property of photons and has evoked research onto the light–matter interaction in both classical and quantum regimes. In classical optics, OAM is related to an optical vortex with a helical phase structure. In quantum optics, photons with a twisted or helical phase structure will carry a quantized OAM. To our knowledge, however, so far, no experiment has demonstrated the fundamental property of the OAM at the single-photon level. In this Letter, we have demonstrated the average photon trajectories of twisted photons in a double-slit interference. We have experimentally captured the double-slit interference process of twisted photons by a time-gated intensified charge-coupled device camera, which is trigged by a heralded detection. Our work provides new perspectives for understanding the micro-behaviors of twisted particles and enables new applications in imaging and sensing.展开更多
A Hardy-like proof of quantum contextuality is a compelling way to see the conflict between quantum theory and noncontextual hidden variables(NCHVs),as the latter predict that a particular probability must be zero,whi...A Hardy-like proof of quantum contextuality is a compelling way to see the conflict between quantum theory and noncontextual hidden variables(NCHVs),as the latter predict that a particular probability must be zero,while quantum theory predicts a nonzero value.For the existing Hardy-like proofs,the success probability tends to 1/2when the number of measurement settings n goes to infinity.It means the conflict between the existing Hardy-like proof and NCHV theory is weak,which is not conducive to experimental observation.Here we advance the study of a stronger Hardy-like proof of quantum contextuality,whose success probability is always higher than the previous ones generated from a certain n-cycle graph.Furthermore,the success probability tends to 1 when n goes to infinity.We perform the experimental test of the Hardy-like proof in the simplest case of n=7 by using a four-dimensional quantum system encoded in the polarization and orbital angular momentum of single photons.The experimental result agrees with the theoretical prediction within experimental errors.In addition,by starting from our Hardy-like proof,one can establish the stronger noncontextuality inequality,for which the quantumclassical ratio is higher with the same n,which provides a new method to construct some optimal noncontextuality inequalities.Our results offer a way for optimizing and enriching exclusivity graphs,helping to explore more abundant quantum properties.展开更多
基金Supported by the National Key R&D Program of China under Grant Nos.2017YFA0303800 and 2017YFA0303700the National Natural Science Foundation of China under Grant Nos.11534006,91750202,11774183 and 11674184the Collaborative Innovation Center of Extreme Optics。
文摘High-dimensional(HD)entanglement provides a very promising way of transcending the limitations of the twodimensional entanglement between qubits for increasing channel capacity in many quantum protocols.In the pursuit of capitalizing on the HD entangled states,one of the central issues is to unambiguously and comprehensively quantilfy and reconstruct them.The full quantum state tomography is a unique solution,but it is undesirable and even impractical because the measurements increase rapidly in d^4 for a bipartite d-dimensional quantum state.Here we present a very efficient and practical tomography method—asymptotical locking tomography(ALT),which can harvest full information of bipartite d-dimensional entangled states by very few measurements less than 2 d^2 only.To showcase the validity and reasonableness of our ALT,we carry out the test with the two-photon spin-orbital angular momentum hyperentangled states in a four-dimensional subspace.Besides high-efficiency and practicality,our ALT is also universal and can be generalized into multipartite HD entanglement and other quantum systems.
基金the National Key R&D Program of China under Grant Nos 2017YFA0303800 and 2017YFA0303700the National Natural Science Foundation of China under Grant Nos 11534006,11774183 and 11674184the Collaborative Innovation Center of Extreme Optics
文摘Ghost imaging functions achieved by means of the spatial correlations between two photons is a new modality in imaging systems. With a small number of photons, ghost imaging is usually realized based on the position correlation of photon pairs produced from the spontaneous parametric down-conversion process. Here we demonstrate a way to realize multi-path ghost imaging by introducing an additional time correlation. Different delays of paths will induce the shift of the coincidence peak, which carries the information about objects. By choosing the suitable coincidence window, we obtain images of three objects simultaneously, with a visibility of 87.2%.This method provides insights and techniques into multi-parameter ghost imaging. It can be applied to other correlated imaging systems, for example, quantum spiral imaging.
基金Supported by the National Key R&D Program of China under Grant Nos 2017YFA0303800 and 2017YFA0303700the National Natural Science Foundation of China under Grant Nos 11534006,11674184,11774183 and 11804187+1 种基金the Natural Science Foundation of Tianjin under Grant No 16JCZDJC31300the Collaborative Innovation Center of Extreme Optics
文摘In recent years,orbital angular momentum(OAM),as a new usable degree of freedom of photons,has been widely applied in both classical optics and quantum optics.For example,digital spiral imaging uses the OAM spectrum of the output beam from the object to restore the symmetry information of the object.However,the related experiments have been carried out in free space so far.Due to the poor anti-noise performance,limited transmission distance and other reasons,the practicability is seriously restricted.Here,we have carried out a digital spiral imaging experiment through a few-mode fiber,to achieve the identification of the symmetry of object by measuring the OAM spectrum of the output beam.In experiment,we have demonstrated the identification of the symmetry of amplitude-only and phase-only objects with the two-,three-and four-fold rotational symmetries.We also give the understanding of the physics.We believe that our work has greatly improved the practical application of digital spiral imaging in remote sensing.
基金Supported by the National Key R&D Program of China under Grant Nos 2017YFA0303800 and 2017YFA0303700the National Natural Science Foundation of China under Grant Nos 11534006,11774183 and 11674184+1 种基金the Natural Science Foundation of Tianjin under Grant No 16JCZDJC31300the Collaborative Innovation Center of Extreme Optics
文摘We present a two-photon interference experiment in a modified Mach-Zehnder （MZ） interferometer in which two Hong-Ou-Mandel effects occur in tandem and construct superposed two-photon states. The signal photons pass both the arms of the MZ interferometer while the idler photons pass one arm only. Interestingly, the probability of the idler photons emerging from any output port still shows a sine oscillation with the two-photon phase difference and it can be characterized only by the indistinguishability of the two-photon amplitudes. We also observe a two-photon interference pattern with a period being equal to the wavelength of the parametric photons instead of the two-photon photonie de Broglie wavelength due to the presence of two-photon phase difference, in particular, with complementary probabilities of finding the two-photon pairs in two output ports. The abundant observations can facilitate a more comprehensive understanding of the two-photon interference.
基金supported by the National Key R&D Program of China (Nos. 2017YFA0303800 and 2017YFA0303700)the National Natural Science Foundation of China (Nos. 11534006,11674184,and 11774183)+1 种基金the Natural Science Foundation of Tianjin(No. 16JCZDJC31300)the Collaborative Innovation Center of Extreme Optics
文摘Optical orbital angular momentum(OAM) is a special property of photons and has evoked research onto the light–matter interaction in both classical and quantum regimes. In classical optics, OAM is related to an optical vortex with a helical phase structure. In quantum optics, photons with a twisted or helical phase structure will carry a quantized OAM. To our knowledge, however, so far, no experiment has demonstrated the fundamental property of the OAM at the single-photon level. In this Letter, we have demonstrated the average photon trajectories of twisted photons in a double-slit interference. We have experimentally captured the double-slit interference process of twisted photons by a time-gated intensified charge-coupled device camera, which is trigged by a heralded detection. Our work provides new perspectives for understanding the micro-behaviors of twisted particles and enables new applications in imaging and sensing.
基金Alexander von Humboldt-StiftungNankai Zhide Foundation+4 种基金Tianjin Research Innovation Project for Postgraduate Students(2019YJSB033)National Key Research and Development Program of China(2017YFA0303700,2017YFA0303800)National Natural Science Foundation of China(11534006,116741841,11774183,11875167,11901317,12075001,12104135)China Postdoctoral Science Foundation(2018M631726,2018M640471)Collaborative Innovation Center of Extreme Optics。
文摘A Hardy-like proof of quantum contextuality is a compelling way to see the conflict between quantum theory and noncontextual hidden variables(NCHVs),as the latter predict that a particular probability must be zero,while quantum theory predicts a nonzero value.For the existing Hardy-like proofs,the success probability tends to 1/2when the number of measurement settings n goes to infinity.It means the conflict between the existing Hardy-like proof and NCHV theory is weak,which is not conducive to experimental observation.Here we advance the study of a stronger Hardy-like proof of quantum contextuality,whose success probability is always higher than the previous ones generated from a certain n-cycle graph.Furthermore,the success probability tends to 1 when n goes to infinity.We perform the experimental test of the Hardy-like proof in the simplest case of n=7 by using a four-dimensional quantum system encoded in the polarization and orbital angular momentum of single photons.The experimental result agrees with the theoretical prediction within experimental errors.In addition,by starting from our Hardy-like proof,one can establish the stronger noncontextuality inequality,for which the quantumclassical ratio is higher with the same n,which provides a new method to construct some optimal noncontextuality inequalities.Our results offer a way for optimizing and enriching exclusivity graphs,helping to explore more abundant quantum properties.
