Multipartite Continuous Variable Quantum Conferencing Network with Entanglement in the Middle

We suggest a continuous variable quantum conferencing network scheme with an entangled source in the middle. Here, the source generates a multipartite entangled state and distributes the modes of the state to an arbitrary number of legitimate network users. The entangled modes that were received and measured by the users share mutual information, which is utilized to generate secure conferencing key between users. The scheme is proven secure against collective attacks on both the untrusted source in the middle and all the quantum links. Simulation results show that the presented scheme can achieve high rate secure conferencing for 100 users within a 400 m-radius community or factory area.

Multipartite entanglement and few-body Hamiltonians

We investigate the possibility to obtain higly multipartite-entangled states as non-degenerate eigenstates of Hamiltonians that involve only short-range and few-body interactions. We study small-size systems (with a number of qubits ranging from three to five) and search for Hamiltonians with a maximally multipartite entangled state (MMES) as a non-degenerate eigenstate. We then find conditions, including bounds on the number of coupled qubits, to build a Hamiltonian with a Greenberger–Horne–Zeilinger (GHZ) state as a non-degenerate eigenstate. We finally comment on possible applications.

CONSTRUCTING MAXIMALLY MULTIQUBIT ENTANGLED STATE VIA BELL-PAIR STATE

Brown et al. and Borras et al. have explored numerical optimization procedures to search for highly entangled five- and six-qubit states. Here, we give a relation between the genuine multiqubit entangled state and Bell state for 4-, 5-, and 6-qubit systems. And the general method to construct maximally multipartite entangled state is also presented.

TELEPORTATION AND CONTROLLED TELEPORTATION WITH MAXIMALLY FOUR-QUBIT ENTANGLEMENT QUANTUM STATES

Recently Paolo Facchi et al.15 presented a maximally multipartite entangled state (MMES). It is shown that some of these states can be utilized for perfect teleportation of arbitrary two-qubit systems and controlled teleportation of an arbitrary one-qubit state. Furthermore, the optimal match measuring basis are given by transformation operator for controlled teleportation.

MULTIPARTITE COHERENT ENTANGLED STATE OF CONTINUOUS VARIABLES: STRUCTURE AND GENERATION

Motivated by the new approach to finding multipartite entangled state representation [Int. J. Mod. Phys. A22, 4481 (2007)], we construct the multipartite coherent entangled state (MCES) of continuous variables which exhibits both coherent state's and entangled state's properties. A protocol of generating such an MCES is proposed by using beam splitters in a sequence. Applications of MCES in studying generalized Wigner function, squeezing and quantum teleportation are discussed.

NEW n-MODE BOSE OPERATOR REALIZATION OF SU(2) LIE ALGEBRA AND ITS APPLICATION IN ENTANGLED FRACTIONAL FOURIER TRANSFORM

We introduce a new n-mode Bose operator realization of SU(2) Lie algebra and link it to the two mutually conjugate multipartite entangled state representations. In so doing we are naturally lead to the n-mode entangle fractional Fourier transform (EFFT), which provides us with a convenient way to deriving the EFFT of quantum-mechanical wave functions.

NEW APPROACH FOR FINDING MULTIPARTITE ENTANGLED STATE REPRESENTATIONS VIA THE IWOP TECHNIQUE

We present a new approach to finding multipartite entangled state representation by decomposing normally ordered Gaussian-form operator in completeness relation, the technique of integration within an ordered product (IWOP) of operators is essential in this searching.