Considering the dipole-dipole coupling intensity between two atoms and the field in the Fock state, the entanglement dynamics between two atoms that are initially entangled in the system of two two-level atoms coupled...Considering the dipole-dipole coupling intensity between two atoms and the field in the Fock state, the entanglement dynamics between two atoms that are initially entangled in the system of two two-level atoms coupled to a single mode cavity in the presence of phase decoherence has been investigated. The two-atom entanglement appears with periodicity without considering phase decoherence, however, the phase decoherence causes the decay of entanglement between two atoms, with the increasing of the phase decoherence coefficient, the entanglement will quickly become a constant value, which is affected by the two-atom initial state. Meanwhile the two-atom quantum state will forever stay in the maximal entangled state when the initial state is proper even in the presence of phase decoherence. On the other hand, the Bell violation and the entanglement do not satisfy the monotonous relation, a large Bell violation implies the presence of a large amount of entanglement under certain conditions, while a large Bell violation corresponds to a little amount of entanglement in certain situations. However, the violation of Bell-CHSH inequality can reach the maximal value if two atoms are in the maximal entangled state, or vice versa.展开更多
We experimentally demonstrate a quantum key distribution protocol using entangled photon pairs in orbital angular momentum(OAM).Here Alice uses a fixed phase hologram to modulate her OAM state on one photon with a spa...We experimentally demonstrate a quantum key distribution protocol using entangled photon pairs in orbital angular momentum(OAM).Here Alice uses a fixed phase hologram to modulate her OAM state on one photon with a spatial light modulator(SLM),while Bob uses the designed N different phase holograms for his N-based keys on the other photon with his SLM.With coincidences,Alice can fully retrieve the keys sent by Bob without reconciliation.We report the experiment results with N=3 and OAM eigenmodes|l=±1>,and discuss the security from the light path and typical attacks.展开更多
基金the Key Program of National Natural Science Foundation of China under Grant No.10534030Key Higher Education Program of Hubei Province under Grant No.Z20052201+1 种基金the Natural Science Foundation of Hubei Province under Grant No.2006ABA055the Postgraduate Program of Hubei Normal University under Grant No.2007D20
文摘Considering the dipole-dipole coupling intensity between two atoms and the field in the Fock state, the entanglement dynamics between two atoms that are initially entangled in the system of two two-level atoms coupled to a single mode cavity in the presence of phase decoherence has been investigated. The two-atom entanglement appears with periodicity without considering phase decoherence, however, the phase decoherence causes the decay of entanglement between two atoms, with the increasing of the phase decoherence coefficient, the entanglement will quickly become a constant value, which is affected by the two-atom initial state. Meanwhile the two-atom quantum state will forever stay in the maximal entangled state when the initial state is proper even in the presence of phase decoherence. On the other hand, the Bell violation and the entanglement do not satisfy the monotonous relation, a large Bell violation implies the presence of a large amount of entanglement under certain conditions, while a large Bell violation corresponds to a little amount of entanglement in certain situations. However, the violation of Bell-CHSH inequality can reach the maximal value if two atoms are in the maximal entangled state, or vice versa.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61271238 and 10904074the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No 20123223110003+3 种基金the University Natural Science Research Foundation of Jiangsu Province under Grant No 11KJA510002the Open Research Fund of National Laboratory of Solid State Microstructures under Grant Nos M25020 and M25022Qinglan Project of Jiangsu Provincethe Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘We experimentally demonstrate a quantum key distribution protocol using entangled photon pairs in orbital angular momentum(OAM).Here Alice uses a fixed phase hologram to modulate her OAM state on one photon with a spatial light modulator(SLM),while Bob uses the designed N different phase holograms for his N-based keys on the other photon with his SLM.With coincidences,Alice can fully retrieve the keys sent by Bob without reconciliation.We report the experiment results with N=3 and OAM eigenmodes|l=±1>,and discuss the security from the light path and typical attacks.
