Quantum Secure Direct Communication Using Six-Particle Maximally Entangled States and Teleportation

The sender shares six-particle maximally entangled states as quantum channel with the receiver. If the quantum channel is secure, the sender performs projective measurements and tells the measurement outcome to the receiver. The receiver performs the unitary transformations and makes projective measurements on his particles to obtain the secret information. Using teleportation, the transmission of three-qubit secret information can be completed in each quantum channel

Generation of maximally entangled states in a two-component Bose-Einstein condensate

We study analytically the generation of maximally entangled states （MESs） formed by a two-component Bose-Einstein condensate （BEC） trapped in an adiabatically driven single potential well. Under the condition of the linear interaction controlled by a driven field being much stronger than the effective nonlinear interaction between the components, MESs, as some particular cases of superpositions of spin coherent states （SSCS）, may emerge periodically along with not only time evolution but also the equidifferent change of the linear coupling strength at a particular time.

Scheme to generate and discriminate a type of multipartite maximally entangled states in ion-trap

This paper proposes a scheme to generate, in an ion-trap, a type of multipartite maximally entangled state which was first introduced by Chen et al. [Chen P X, Zhu S Y and Guo G C 2006 Phys. Rev. A 74 032324]. The maximum entanglement property of these states is examined. It also demonstrates how to discriminate among these states in the ion-trap.

A Criterion to Identify Maximally Entangled Four-Qubit State

Paolo Facchi,et al.[Phys.Rev.A 77 (2008)060304(R)]presented a maximally multipartite entangledstate (MMES).Here,we give a criterion for the identification of maximally entangled four-qubit states.Using thiscriterion,we not only identify some existing maximally entangled four-qubit states in the literature,but also find severalnew maximally entangled four-qubit states as well.

On Topics in Quantum Games

This work concentrates on simultaneous move non-cooperating quantum games. Part of it is evidently not new, but it is included for the sake self consistence, as it is devoted to introduction of the mathematical and physical grounds of the pertinent topics, and the way in which a simple classical game is modified to become a quantum game (a procedure referred to as a quantization of a classical game). The connection between game theory and information science is briefly stressed, and the role of quantum entanglement (that plays a central role in the theory of quantum games), is exposed. Armed with these tools, we investigate some basic concepts like the existence (or absence) of a pure strategy and mixed strategy Nash equilibrium and its relation with the degree of entanglement. The main results of this work are as follows: 1) Construction of a numerical algorithm based on the method of best response functions, designed to search for pure strategy Nash equilibrium in quantum games. The formalism is based on the discretization of a continuous variable into a mesh of points, and can be applied to quantum games that are built upon two-players two-strategies classical games, based on the method of best response functions. 2) Application of this algorithm to study the question of how the existence of pure strategy Nash equilibrium is related to the degree of entanglement (specified by a continuous parameter γ ). It is shown that when the classical game GC has a pure strategy Nash equilibrium that is not Pareto efficient, then the quantum game GQ with maximal entanglement (γ = π/2) has no pure strategy Nash equilibrium. By studying a non-symmetric prisoner dilemma game, it is found that there is a critical value 0γc such that for γγc there is a pure strategy Nash equilibrium and for γ≥γc there is no pure strategy Nash equilibrium. The behavior of the two payoffs as function of γ starts at that of the classical ones at (D, D) and approaches the cooperative classical ones at (C, C) (C = confess, D = don’t confess). 3) We then study Bayesian quantum games and show that under certain conditions, there is a pure strategy Nash equilibrium in such games even when entanglement is maximal. 4) We define the basic ingredients of a quantum game based on a two-player three strategies classical game. This requires the introduction of trits (instead of bits) and quantum trits (instead of quantum bits). It is proved that in this quantum game, there is no classical commensurability in the sense that the classical strategies are not obtained as a special case of the quantum strategies.

Twist-teleportation-based local discrimination of maximally entangled states

In this work,we study the local distinguishability of maximally entangled states(MESs).In particular,we are concerned with whether any fixed number of MESs can be locally distinguishable for sufficiently large dimensions.Fan and Tian et al.have already obtained two satisfactory results for the generalized Bell states(GBSs)and the qudit lattice states when applied to prime or prime power dimensions.We construct a general twist-teleportation scheme for any orthonormal basis with MESs that is inspired by the method used in[Phys.Rev.A 70,022304(2004)].Using this teleportation scheme,we obtain a sufficient and necessary condition for one-way distinguishable sets of MESs,which include the GBSs and the qudit lattice states as special cases.Moreover,we present a generalized version of the results in[Phys.Rev.A 92,042320(2015)]for the arbitrary dimensional case.

An Economical Scheme for Cloning an Unknown M-Qudit Equatorial-Like State with Assistance

We propose a scheme to realize quantum cloning of an unknown M-qudit equatorial-like entangled state. The first stage of the protocol requires teleportation. After the teleportation is accomplished, the receiver can reestablish the original state. In the second stage of the protocol, with the assistance （through a single-particle projective measurement） of the preparer, the perfect copy of an original state can be produced at the site of the sender. Our scheme requires a single maximally entangled qudit pair as the quantum channel and three dits classical communication. The scheme is feasible at the expense of consuming local resources which include M - 1 ancillary qudits introduced by the receiver and additional bi-qudit operations. Moreover, we construct a sort of unitary transformations which ensure ancillary qudits are not necessarily introduced by the sender. Comparing to the previous protocols, the proposed protocol is economical due to that the cost of both quantum nonlocal resources and classical communication is lowest.

State-Independent Proofs of Bell＇s Theorem Without Inequalities and Bell Inequality for Four-Qubit System

A state-dependent proof of Bell's theorem without inequalities using the product state of any two maximally entangled states (Bell states) of two qubits for two observers in an ideal condition, each of which possesses two qubits,is proposed. It is different from the other proofs in which there exists a fundamental requirement that certain specific suitable Bell states have been chosen. Moreover, in any non-ideal situation, a common Bell inequality independent of the choices of the 16-product states is derived, which is used to test the contradiction between quantum mechanics and local reality theory in the reach of current experimental technology.

A note on the Bloch representation of absolutely maximally entangled states

Multipartite entanglement was not only an interesting phenomenon in quantum physics,but also a key resource in quantum information theory,which can allow for novel quantum advantages in quantum information processing.One of the most striking phenomena in multipartite entangled systems is that even if one acquires complete knowledge of the

A Scheme of Controlled Quantum State Swapping

A scheme for controlled quantum state swapping is presented using maximally entangled five-qubit state,i.e.,Alice wants to transmit an entangled state of particle a to Bob and at the same time Bob wants to transmit an entangled state of particle b to Alice via the control of the supervisor Charlie.The operations used in this swapping process including C-not operation and a series of single-qubit measurements performed by Alice,Bob,and Charlie.