A Practical Quantum Network Coding Protocol Based on Non-Maximally Entangled State

In many earlier works,perfect quantum state transmission over the butterfly network can be achieved via quantum network coding protocols with the assist of maximally entangled states.However,in actual quantum networks,a maximally entangled state as auxiliary resource is hard to be obtained or easily turned into a non-maximally entangled state subject to all kinds of environmental noises.Therefore,we propose a more practical quantum network coding scheme with the assist of non-maximally entangled states.In this paper,a practical quantum network coding protocol over grail network is proposed,in which the non-maximally entangled resource is assisted and even the desired quantum state can be perfectly transmitted.The achievable rate region,security and practicability of the proposed protocol are discussed and analyzed.This practical quantum network coding protocol proposed over the grail network can be regarded as a useful attempt to help move the theory of quantum network coding towards practicability.

Quantum multicast schemes of different quantum states via non-maximally entangled channels with multiparty involvement

Due to the unavoidable interaction between the quantum channel and its ambient environment,it is difficult to generate and maintain the maximally entanglement.Thus,the research on multiparty information transmission via non-maximally entangled channels is of academic value and general application.Here,we utilize the non-maximally entangled channels to implement two multiparty remote state preparation schemes for transmitting different quantum information from one sender to two receivers synchronously.The first scheme is adopted to transmit two different four-qubit cluster-type entangled states to two receivers with a certain probability.In order to improve success probabilities of such multicast remote state preparation using non-maximally entangled channels,we put forward the second scheme,which deals with the situation that is a synchronous transfer of an arbitrary single-qubit state and an arbitrary two-qubit state from one sender to two receivers.In particular,its success probability can reach 100%in principle,and independent of the entanglement degree of the shared non-maximally entangled channel.Notably,in the second scheme,the auxiliary particle is not required.

Probabilistic and Hierarchical Quantum Information Splitting Based on the Non-Maximally Entangled Cluster State

With the emergence of classical communication security problems,quantum communication has been studied more extensively.In this paper,a novel probabilistic hierarchical quantum information splitting protocol is designed by using a non-maximally entangled four-qubit cluster state.Firstly,the sender Alice splits and teleports an arbitrary one-qubit secret state invisibly to three remote agents Bob,Charlie,and David.One agent David is in high grade,the other two agents Bob and Charlie are in low grade.Secondly,the receiver in high grade needs the assistance of one agent in low grade,while the receiver in low grade needs the aid of all agents.While introducing an ancillary qubit,the receiver’s state can be inferred from the POVM measurement result of the ancillary qubit.Finally,with the help of other agents,the receiver can recover the secret state probabilistically by performing certain unitary operation on his own qubit.In addition,the security of the protocol under eavesdropping attacks is analyzed.In this proposed protocol,the agents need only single-qubit measurements to achieve probabilistic hierarchical quantum information splitting,which has appealing advantages in actual experiments.Such a probabilistic hierarchical quantum information splitting protocol hierarchical is expected to be more practical in multipartite quantum cryptography.

An efficient scheme for multi-party quantum state sharing via non-maximally entangled states

We present a new scheme for investigating the usefulness of non-maximally entangled states for multi-party quantum state shar-ing in a simple and elegant manner.In our scheme,the sender,Alice shares n various probabilistic channels composed of non-maximally entangled states with n agents in a network.Our protocol involves only Bell-basis measurements,single qubit measurements,and a two-qubit unitary transformation operated by free optional agents.Our scheme is a more convenient realiza-tion because no other multipartite joint measurements are needed.Furthermore,in our scheme various probabilistic channels lessen the requirement for quantum channels,which makes it more practical for physical implementation.

Teleportation of two-atom entangled state in resonant cavity quantum electrodynamics

An alternative scheme is presented for teleportation of a two-atom entangled state in cavity quantum electrodynamics （QED）. It is based on the resonant atom-cavity field interaction. In the scheme, only one cavity is involved, and the number of the atoms needed to be detected is decreased compared with the previous scheme. Since the resonant atom-cavity field interaction greatly reduces the interaction time, the decoherence effect can be effectively suppressed during the teleportation process. The experimental feasibility of the scheme is discussed. The scheme can easily be generalized to the teleportation of N-atom Greeninger-Horne-Zeilinger （GHZ） entangled states. The number of atoms needed to be detected does not increase as the number of the atoms in the GHZ state increases.

Entanglement diversion and quantum teleportation of entangled coherent states

The proposals on entanglement diversion and quantum teleportation of entangled coherent states are presented. In these proposals, the entanglement between two coherent states, ｜α〉 and ｜-α〉, with the same amplitude but a phase difference of π is utilized as a quantum channel. The processes of the entanglement diversion and the teleportation are achieved by using the 50/50 symmctric beam splitters, the phase shifters and the photodetectors with the help of classical information.

Probabilistic remote preparation of a two-atom entangled state

A scheme for remotely preparing a two-atom entangled state via entanglement swapping in cavity quantum electronic dynamics （QED） with the help of separate measurements is proposed. And the effect of cavity decay is eliminated in our scheme.

Probabilistic teleportation of an arbitrary GHZ-class state with a pure entangled two-particle quantum channel and its application in quantum state sharing

This paper presents a scheme for probabilistic teleportation of an arbitrary GHZ-class state with a pure entangled two-particle quantum channel. The sender Alice first teleports the coefficients of the unknown state to the receiver Bob, and then Bob reconstructs the state with an auxiliary particle and some unitary operations if the teleportation succeeds. This scheme has the advantage of transmitting much less particles for teleporting an arbitrary GHZ-class state than others. Moreover, it discusses the application of this scheme in quantum state sharing.

Teleportation of atomic entangled states with a thermal cavity

We propose a most simple and experimentally feasible scheme for teleporting unknown atomic entangled states in driven cavity quantum electrodynamics （QED）. In our scheme, the joint Bell-state measurement （BSM） is not required, and the successful probability can reach 1.0. Furthermore, the scheme is insensitive to the cavity decay and the thermal field.

Entropy evolvement properties in a system of Schrodinger cat state light field interacting with two entangled atoms

The field entropy can be regarded as a measurement of the degree of entanglement between the light field and the atoms of a system which is composed of two-level atoms initially in an entangled state interacting with the Schroedinger cat state. The influences of the strength of light field and the phase angle between the two coherent states on the field entropy are discussed by using numerical calculations. The result shows that when the strength of light field is large enough the field entropy is not zero and the degrees of entanglement between the atoms and the three different states of the light fields are equal. When the strength of the light field is small, the degree of entanglement is maximum in a system of the two entangled atoms interacting with an odd coherent state; it is intermediate for a system of the two entangled atoms interacting with the Yurke-Stoler coherent state, and it is minimum in a system of the two entangled atoms interacting with an even coherent state.

A scheme for transferring an unknown atomic entangled state via cavity quantum electrodynamics

In this paper, we propose a scheme for transferring an unknown atomic entangled state via cavity quantum electrodynamics （QED）. This scheme, which has a successful probability of 100 percent, does not require Bell-state measurement and performing any operations to reconstruct an initial state. Meanwhile, the scheme only involves atomfield interaction with a large detuning and does not require the transfer of quantum information between the atoms and cavity. Thus the scheme is insensitive to the cavity field states and cavity decay. This scheme can also be extended to transfer ring an entangled state of n-atom.

Efficient scheme for teleportation of an unknown N-atom state via a two-atom entangled state without the Bell-state measurement in cavity QED

We propose a scheme for teleportation of an unknown N-atom state using a two-atom entangled state within a cavity QED and show the feasibility in experiment. Our scheme does not involve the Bell-state measurement and is insensitive to the cavity decay, which is important from the experimental point of view. Another feature of the scheme is that teleporting a N-atom state just requires a small amount of entanglement （i,e. a two-atom entangled state） and less classical bits （two bits）.

A scheme for approximate conditional teleportation of entangled two-mode cavity state without Bell state measurement

An alternative scheme to approximately conditionally teleport entangled two-mode cavity state without Bell state measurement in cavity QED is proposed. The scheme is based on the resonant interaction of a ladder-type three-level atom with two bimodal cavities. The entangled cavity state is reconstructed with only one atom interacting with the two cavities successively.

Teleportation of a two-atom entangled state using a single EPR pair in cavity QED

We propose a scheme for teleporting a two-atom entangled state in cavity quantum electrodynamics （QED）, In the scheme, we choose a single Einstein Podolsky Rosen （EPR） pair as the quantmn channel which is shared by the sender and the receiver. By using the atom cavity-field interaction and introducing an additional atom, we can teleport the two-atom entangled state successfully with a probability of 1.0. Moreover, we show that the scheme is insensitive to cavity decay and thermal field.

Quantum dense coding using a peculiar tripartite entangled state

Following a recent proposal （Phys. Left. A 346 （2005） 330） about quantum dense coding using a tripartite entangled GHZ state and W state, this paper proposes an experimentally feasible scheme for dense coding in cavity QED by using another peculiar tripartite entangled state. In the scheme the atoms interact simultaneously with a highly detuned cavity mode with the assistance of a classical field, the successful probability of dense coding scheme with this peculiar tripartite entangled state equals 1.

Dynamical nonlocality of the entangled coherent state in the phase damping model

This paper studies the dynamics of nonlocality for a bosonic entangled coherent state in a phase damping model. The density operator of the system is solved by using a superoperator method. The dynamics of nonlocality for the bosonic entangled coherent state is uncovered by the Bell operator based on the pseudospin operator of a light field. The dynamics of the nonlocality for this state has also been studied by other Bell operators. The result of the numerical calculations of the Bell function shows that the quantum nonlocality heavily depends on the chosen Bell operator.

Scheme for realizing assisted cloning of an unknown two-atom entangled state via cavity QED

This paper proposes a scheme where one can realize quantum cloning of an unknown two-atom entangled state with assistance of a state preparer in cavity QED. The first stage of the scheme requires usual teleportation. In the second stage of the scheme, with the assistance of the preparer, the perfect copies of an unknown atomic entangled state can be produced.

A Coding and Automatic Error-Correction Circuit Based on the Five-Particle Entangled State

In this paper, we discuss the concepts of quantum coding and error correction for a five-particle entangled state. Error correction can correct bit-reverse or phase-flip errors of one and two quantum states and is no longer limited to only one quantum state. We encode a single quantum state into a five-particle entangled state before being transferred to the sender. We designed an automatic error-correction circuit to correct errors caused by noise. We also simplify the design process for a multiple quantum error-correction circuit. We compare error-correction schemes for five and three entangled particles in terms of efficiency and capabilities. The results show that error-correction efficiency and fidelity are im- proved.

Time evolution of angular momentum coherent state derived by virtue of entangled state representation and a new binomial theorem

We study how can an angular momentum coherent state |τ> keeps its form-invariant during time evolution governed by the Hamiltonian H = f(t)J++ f^*(t)J-+ g(t)Jz. We discuss this topic in the context of boson realization of |τ>. By employing the entangled state representation |ζ> and deriving a new binomial theorem involving two-subscript Hermite polynomials, we derive the wave function <ζ|τ>, which turns out to be a single-subscript Hermite polynomial. Based on this result the maintenance of angular momentum coherent state during time evolution is examined, and the value of τ(t) is totally determined by the parameters involved in the Hamiltonian.