Probabilistic Teleportation of an Unknown Two-Particle State with a Four-Particle Pure Entangled State and Positive Operator Valued Measure

We propose a scheme for probabilistic teleportation of an unknown two-particle state with a four-particle pure entangled state and positive operator valued measure （POVM）. In this scheme the teleportation of an unknown two-particle state can be realized with certain probability by performing two Bell state measurements, a proper POVM and a unitary transformation.

Efficient Three-Party Quantum Secret Sharing with Single Photons

A scheme for three-party quantum secret sharing of a private key is presented with single photons. The agent Bob first prepares a sequence of single photons with two biased bases and then sends them to the boss Alice who checks the security of the transmission with measurements and produces some decoy photons by rearranging the orders of some sample photons. Alice encodes her bits with two unitary operations on the photons and then sends them to the other agent. The security of this scheme is equivalent to that in the modified Bennett Brassard 1984 quantum key distribution protocol. Moreover, each photon can carry one bit of the private key and the intrinsic efficiency for qubits and the total efficiency both approach the maximal value 100% when the number of the bits in the key is very large.

Teleportation of Multi-qudit Entangled States

We propose a method to realize the teleportation of an unknown entangled state that consists of many qudits through a partially entangled-qudit quantum channel with the help of 2 log2 d-bit classical communication. The operations used in the teleportation process include a generalized Bell-state measurement and a series of singlequdit π-measurements performed by Alice, a series of generalized qudit-Pauli gates and two-level unitary gates, as well as a qubit measurement performed by Bob. For a maximally entangled quantum channel, the successful probability of the teleportation becomes unit.

Teleportation for an Ionic Entangled Internal State by Entanglement Swapping

We present an effective scheme to teleport an unknown ionic entangled internal state via trapped ions without joint Bell-state measurement. In the constructed quantum channel process, we adopt entanglement swapping to avoid decrease of entanglement during the distribution of particles. Thus our scheme provides new prospects for quantum teleportation over longer distance. The distinct advantages of our scheme are that our scheme is insensitive to heating of vibrational mode and can be generalized to teleport an N-ion electronic entangled GHZ class state. Furthermore, in our scheme the success probability can reach 1.

Remote Three-Atom Information Concentration without Bell-State Measurement

We propose a scheme for information concentration of three remote two-level atoms in cavity QED. Our scheme does not involve the Bell-state measurement. During the interaction between atom and cavity, the cavity frequency is largely detuned from the atomic transition frequency, thus the scheme is insensitive to both the cavity decay and the thermal field. The idea can also be used to realize the remote information concentration of trapped ions.

Teleportation of Entangled States through Divorce of Entangled Pair Mediated by a Weak Coherent Field in a High-Q Cavity

We propose a scheme to partially teleport an unknown entangled atomic state. A high-Q cavity, supporting one mode of a weak coherent state, is needed to accomplish this process. By partial teleportation we mean that teleportation will occur by changing one of the partners of the entangled state to be teleported. The entangled state to be teleported is composed by one pair of particles, we called this surprising characteristic of maintaining the entanglement, even when one of the particle of the entangled pair being teleported is changed, of divorce of entangled states.

Quantum State Sharing by Using Two-Mode and Single-Mode Squeezed State Lights

We propose a quantum state sharing scheme for continuous variables using bright two-mode squeezed state and single-mode squeezed state light. The squeezing of a single-mode state is applied to enhance the security of information in quantum teleportation network. The signal-to-noise ratio of communication and the fidelity between the secret and reconstruction state are analysed. It is shown that both the receivers of Bob and Charlie cannot extract information with a high signal-to-noise ratio because of the large noise come from the other quadrature component of single mode squeezed state. Anyone of Bob and Charlie can retrieve the quantum state with a high signal-to-noise ratio if and only if the other one cooperates with the measurement.

Fidelity of Quantum Teleportation for Single-Mode Squeezed State Light

The fidelity of quantum teleportation of a single-mode squeezed state of light is calculated based on the general theory of quantum-mechanical measurement in the Schrodinger picture. It is shown that the criterion for the nonclassical state teleportation is different from that for coherent state. F = 1/2 is no longer the rigorous boundary between classical and quantum teleportation for a squeezed state of light. When the quantum entanglement of an Einstein-Podolsky-Rosen （EPR） beam used for teleportation and the parameters of the system are given, the fidelity depends on the squeezing of the input squeezed state. The higher the squeezing is, the smaller the fidelity is, and the lower the classical limitation of fidelity is. The dependence of the optimum gain for teleporting a squeezed vacuum state upon the EPR entanglement is also calculated. The results obtained provide important references for designing experimental systems of teleporting a non-classical state and judging the quality of the teleported quantum state.

Entanglement Swapping and Concentration in Multi-Pair Bose-Einstein Condensates

We propose a scheme of entanglement swapping and concentration in a system consisting of multi-pair entangled trapped Bose-Einstein condensates （BECs）. In this scheme, entanglement swapping is accomplished by using interference-pattern joint measurements and detecting the total number of condensed atoms leaking out of relevant traps while entanglement concentration is realized by controlling inter-atomic nonlinear and tunnelling interactions. Three- and four-palr BEC schemes are investigated in detail. It is found that with the increasing number of the entangled pairs, the region of entanglement concentration is broadened and the amount of concentrated entanglement is enhanced.