Quantum Cloning of an Unknown Two-Particle Entangled State with Assistance

We propose a protocol where one can realize quantum cloning of an unknown two-particle entangled state and its orthogonal-complement state with assistance offered by a state preparer. The first stage of the protocol requires usual teleportation using a (or two) four-particle entangled state(s) as quantum channel(s). In the second stage of the protocol, with the assistance (through a two-particle projective measurement) of the preparer, the perfect copies and complement copies of an unknown state can be produced.     

Quantum Teleportation of an Unknown Two-Atom Entangled State Using Four-Atom Cluster State

A simply protocol for quantum teleportation of an unknown two-atom entangled state using four-atom cluster state is investigated in cavity quantum electrodynamics (QED). In this protocol, by using a one-dimensional maximally four-atom cluster state as quantum channel, an unknown two-atom entangled state can be transmitted from the sender (Alice) to the receiver without apparent joint Bell-state measurement. According to the results measured by the sender, the receiver can obtain the original state with unit successful probability. The important features of our scheme can also be demonstrated in ion trap system.     

Teleportation of an Unknown Atomic Entangled State Without Any Joint Bell-state Measurement via a Cluster State

An experimentally feasible scheme for teleportation of an unknown two-atom entangled state is proposed. Our scheme uses a duster state as the quantum channel, where we do not need any joint Bell-state measurement. Moreover the successful probability and fidelity of teleportation can both reach 1.0. The current scheme can be realized within the current experimental technology.     

Controlled Quantum Teleportation of a One-Particle Unknown State via a Three-Particle Entangled State

A kind of three-particle entangled state is applied as quantum channel of the controlled quantum teleporration of a one-particle unknown state. The one-particle unknown state is transmitted from the sender to the recipient under the control of the supervisor. After the sender makes Bell-state measurement and the supervisor performs von Neumann measurement, the recipient carries out unitary transformation on his own particle depending on classical information from the sender and the supervisor. The teleportation cannot be completed successfully by the recipient if the supervisor does not agree to cooperate. The roles of the recipient and the supervisor may be exchanged in this scheme. The scheme is flexible and feasible because the sequence of manipulation of the sender and the supervisor may be exchanged and only simple unitary transformation is included.     

Controlled Quantum Teleportation of a One-Particle Unknown State via a Three-Particle Entangled State

A kind of three-particle entangled state is applied as quantum channel of the controlled quantum teleportation of a one-particle unknown state. The one-particle unknown state is transmitted from the sender to the recipient under the control of the supervisor. After the sender makes Bell-state measurement and the supervisor performs von Neumann measurement, the recipient carries out unitary transformation on his own particle depending on classical information from the sender and the supervisor. The teleportation cannot be completed successfully by the recipient if the supervisor does not agree to cooperate. The roles of the recipient and the supervisor may be exchanged in this scheme. The scheme is flexible and feasible because the sequence of manipulation of the sender and the supervisor may be exchanged and only simple unitary transformation is included.     

Teleporting an Unknown Two-qubit Entangled State via Ion-Trap Systems

We propose a scheme for teleportation of an unknown two-qubit entangled state via trapped ions. In this scheme, we use the GHZ state as a quantum channel and the success probability can reach 1. The distinct advantage of our scheme is insensitive to the heating of the vibrational mode. In addition, Bell-state measurement is not required.     

连续变量量子纠缠态的非对称量子克隆

该文讨论了连续变量量子纠缠态非对称克隆过程,从理论上讨论了在Local e-cloner方案中,入射和出射分束器的反射率可变情况下的纠缠态克隆,并利用纠缠不可分判据分析了所获得的非对称克隆纠缠态的纠缠特性.结果指出,克隆得到的两组纠缠态的纠缠特性不相同.     

Scheme for Implementing Assisted Cloning of an Unknown Tripartite Entangled State

In this paper, we propose a protocol which can realize quantum cloning of an unknown tripartite entangled state and its orthogonal complement state with assistance from a state preparer. The first stage of the protocol requires usual teleportation via three entangled particle pairs as quantum channel. In the second stage of the protocol, the perfect copies and complement copies of an unknown state can be produced with the assistance (through a tripartite projective measurement) of the state preparer. We also present a scheme for the teleportation by using non-maximally entangled quantum channel. It is shown that the clones and complement clones of the unknown state can be obtained with certain probability in the latter scheme.     

Optimal Conclusive Teleportation of an Arbitrary d-Dimensional N-Particle Unknown State via a Partially Entangled Quantum Channel

In the paper we generalize the standard teleportation to the conclusive teleportation case which can teleportan arbitrary d-dimensional N-particle unknown state via the partially entangled quantum channel. We show that onlyif the quantum channel satisfies a constraint condition can the most general d-dimensional N-particle unknown state beperfect conclusively teleported. We also present a method for optimal conclusively teleportation of the N-particle statesand for constructing the joint POVM which can discern the quantum states on the sender's (Alice's) side. Two typicalexamples are given so that one can see how our method works.     

Quantum Sharing an Unknown Multi-Particle State via POVM

Our purpose in this paper is to present a new tripartite quantum state sharing using partially quantum resources. The first scheme is to probabilistically split an unknown n-particle state using pre-shared a partially entangled four-particle cluster state as quantum resource by constructing some proper POVM. This scheme is further extended to share an unknown multi-particle cluster state using different states as quantum resources. Our schemes with general quantum channels are useful for various quantum information processing and quantum network tasks.     

Quantum Teleportation via Hybrid Entangled States

In this paper, we study quantum teleportation of atomic states via a hybrid entangled state (HES) involving an atom and a cavity field. And we investigate how to implement controlled phase (CP) gates between atomic internal states and coherent states of cavity field. We also discuss the methods of distinguishing coherent states |±α〉in a cavity. Finally, a brief discussion about the feasibility of this scheme in experiment is presented.     

Deterministic Joint Assisted Cloning of Unknown Two-Qubit Entangled States

We present two schemes for perfect cloning unknown two-qubit and general two-qubit entangled states with assistance from two state preparers, respectively. In the schemes, the sender wish to teleport an unknown two-qubit (or general two-qubit) entangled state which from two state preparers to a remote receiver, and then create a perfect copy of the unknown state at her place. The schemes include two stages. The first stage of the schemes requires usual teleportation. In the second stage, to help the sender realize the quantum cloning, two state preparers perform two-qubit projective measurements on their own qubits which from the sender, then the sender can acquire a perfect copy of the unknown state. To complete the assisted cloning schemes, several novel sets of mutually orthogonal basis vectors are introduced. It is shown that, only if two state preparers collaborate with each other, and perform projective measurements under suitable measuring basis on their own qubit respectively, the sender can create a copy of the unknown state by means of some appropriate unitary operations. The advantage of the present schemes is that the total success probability for assisted cloning a perfect copy of the unknown state can reach 1.     

Quantum Teleportation via Hybrid Entangled States

In this paper, we study quantum teleportation of atomic states via a hybrid entangled state (HES) involving an atom and a cavity field. And we investigate how to implement controlled phase (CP) gates between atomic internal Finally, a brief discussion about the feasibility of this scheme in experiment is presented.     

Assisted Cloning and Orthogonal Complementing of an Arbitrary Unknown Two-Qubit Entangled State

Based on A.K. Pati‘s original idea [Phys. Rev. A 61 (2000) 022308] on single-qubit-state-assisted clone, very recently Zhan has proposed two assisted quantum cloning protocols of a special class of unknown two-qubit entangled states [Phys. Lett. A 336 (2005) 317]. In this paper we further generalize Zhan‘s protocols such that an arbitrary unknown two-qubit entangled state can be treated.     

Assisted Cloning and Orthogonal Complementing of an Arbitrary Unknown Two-Qubit Entangled State

Based on A.K. Pati＇s original idea [Phys. Rev. A 61 （2000） 022308] on single-qubit-state-assisted clone, very recently Zhan has proposed two assisted quantum cloning protocols of a special class of unknown two-qubit entangled states [Phys. Lett. A 336 （2005） 317]. In this paper we further generalize Zhan＇s protocols such that an arbitrary unknown two-qubit entangled state can be treated.     

Teleportation of Two-Particle Entangled State via Cluster State

In this paper,two schemes for teleporting an unknown two-particle entangled state from the sender (Alice)to the receiver (Bob) via a four-particle entangled cluster state are proposed.In these two schemes,the unknown twoparticle entangled state can be teleported perfectly.The successful probabilities and fidelities of the schemes can reach unity.     

Schemes for Teleportation of an Unknown Single-Qubit Quantum State by Using an Arbitrary High-Dimensional Entangled State

We propose a scheme to teleport an unknown single-qubit state by using a high-dimensional entangled state as the quantum channel. As a special case, a scheme for teleportation of an unknown single-qubit state via three-dimensional entangled state is investigated in detail. Also, this scheme can be directly generalized to an unknown f-dimensional state by using a d-dimensional entangled state （d〉f） as the quantum channel.     

Probabilistic Teleportation of an Arbitrary Unknown Two-Qubit State via Positive Operator-Valued Measure and Two Non-maximally Entangled States

We present a scheme for probabilistically teleporting an arbitrary unknown two-qubit state through a quantum channel made up of two nonidentical non-maximally entangled states. In this scheme, the probabilistic teleportation is realized by using a proper positive operator-valued measure instead of usual projective measurement.     

Probabilistic Teleportation of an Arbitrary Unknown Two-Qubit State via Positive Operator-Valued Measure and Two Non-maximally Entangled States

We present a scheme for probabilistically teleporting an arbitrary unknown two-qubit state through a quantum channel made up of two nonidentical non-maximally entangled states. In this scheme, the probabilistic teleportation is realized by using a proper positive operator-valued measure instead of usual projective measurement.