Entanglement purification is to distill high-quality entangled states from low-quality entangled states.It is a key step in quantum repeaters,determines the efficiency and communication rates of quantum communication ...Entanglement purification is to distill high-quality entangled states from low-quality entangled states.It is a key step in quantum repeaters,determines the efficiency and communication rates of quantum communication protocols,and is hence of central importance in long-distance communications and quantum networks.In this work,we report the first experimental demonstration of deterministic entanglement purification using polarization and spatial mode hyperentanglement.After purification,the fidelity of polarization entanglement arises from 0.268±0.002 to 0.989±0.001.Assisted with robust spatial mode entanglement,the total purification efficiency can be estimated as 10^(9) times that of the entanglement purification protocols using two copies of entangled states when one uses the spontaneous parametric down-conversion sources.Our work may have the potential to be implemented as a part of full repeater protocols.展开更多
Bell＇s theorem argues the existence of quantum nonlocality which goes basically against the hidden variable theory （HVT）. Many experiments have been done via testing the violations of Bell＇s inequalities to statis...Bell＇s theorem argues the existence of quantum nonlocality which goes basically against the hidden variable theory （HVT）. Many experiments have been done via testing the violations of Bell＇s inequalities to statistically verify the Bell＇s theorem. Alternatively, by testing the Hardy＇s ladder proofs we experimentally demonstrate the deterministic violation of HVT and thus confirm the quantum nonlocality. Our tests are implemented with non-maximal entangled photon pairs generated by spontaneous parametric down conversions （SPDCs）. We show that the degree freedom of photon entanglement could be significantly enhanced by using interference filters. As a consequence, the Hardy＇s ladder proofs could be tested and Bell＇s theorem is verified robustly. The probability of violating the locality reach to 41.9%, which is close to the expectably ideal value 46.4% for the photon pairs with degree of entanglement e = 0.93. The higher violating probability is possible by further optimizing the experimental parameters.展开更多
基金supported by the National Key Research and Development Program of China(2021YFE0113100 and 2017YFA0304100)the National Natural Science Foundation of China(11774335,11734015,11874345,11821404,11904357,11974189,12174367,and 12175106)+4 种基金the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(CAS,QYZDYSSW-SLH003)Science Foundation of the CAS(ZDRW-XH-2019-1)the Fundamental Research Funds for the Central UniversitiesUSTC Tang ScholarshipScience and Technological Fund of Anhui Province for Outstanding Youth(2008085J02)。
文摘Entanglement purification is to distill high-quality entangled states from low-quality entangled states.It is a key step in quantum repeaters,determines the efficiency and communication rates of quantum communication protocols,and is hence of central importance in long-distance communications and quantum networks.In this work,we report the first experimental demonstration of deterministic entanglement purification using polarization and spatial mode hyperentanglement.After purification,the fidelity of polarization entanglement arises from 0.268±0.002 to 0.989±0.001.Assisted with robust spatial mode entanglement,the total purification efficiency can be estimated as 10^(9) times that of the entanglement purification protocols using two copies of entangled states when one uses the spontaneous parametric down-conversion sources.Our work may have the potential to be implemented as a part of full repeater protocols.
基金supported by the National Natural Science Foundation of China(Grant Nos.61308008,91321104,U1330201 and 11174373)the National Fundamental Research Program of China(Grant No.2010CB923104)
文摘Bell＇s theorem argues the existence of quantum nonlocality which goes basically against the hidden variable theory （HVT）. Many experiments have been done via testing the violations of Bell＇s inequalities to statistically verify the Bell＇s theorem. Alternatively, by testing the Hardy＇s ladder proofs we experimentally demonstrate the deterministic violation of HVT and thus confirm the quantum nonlocality. Our tests are implemented with non-maximal entangled photon pairs generated by spontaneous parametric down conversions （SPDCs）. We show that the degree freedom of photon entanglement could be significantly enhanced by using interference filters. As a consequence, the Hardy＇s ladder proofs could be tested and Bell＇s theorem is verified robustly. The probability of violating the locality reach to 41.9%, which is close to the expectably ideal value 46.4% for the photon pairs with degree of entanglement e = 0.93. The higher violating probability is possible by further optimizing the experimental parameters.
