W-class States Research Articles

Teleportation of a specific family of tripartite entangled pure states via a five-qubit cluster state

We propose teleporting a specific family of tripartite entangled pure states, which include both the Greenberger–Horne–Zeilinger (GHZ) state and the W-class state, with the five-qubit cluster state. In this scheme, two different measurement strategies are introduced and the successful probability of both is one theoretically. In cavity quantum electrodynamics (QED), we propose generating the five-qubit cluster state and discuss the local measurement of the Bell state and the five-qubit cluster state. It is shown that our scheme may be realizable based on present cavity QED technology. In future, our scheme may be useful for establishing general tripartite entanglement in remote nodes of the communication network.

QUANTUM INFORMATION PROCESSING IN AN ARRAY OF SUPERCONDUCTING TRANSMISSION LINE RESONATORS

We consider a one-dimensional array of superconducting transmission line resonators (TLRs). The TLRs are coupled by current-biased Josephson junctions, which act as tunable couplers between each two nearest TLRs, and a superconducting qubit is fabricated in the center of each TLR. We show that some important quantum information processing, such as quantum state transfer and preparation of remote entanglement, can be achieved in this system, and we also propose a scheme for generating the W-class states.

Preparation of multi-atom specially entangled W-class state and splitting quantum information

We give a protocol to prepare specially entangled W-class state of multi-atom which can be used to exactly teleport an arbitrarily unknown two-level two-atom state. During the process, the quantum information is split into n parts and the original quantum information can be sent to anyone of the n recipients with the other n-1 recipients’ collaboration. In addition, we will give a suggestion to realize this scheme via QED cavity.

PREPARATION AND MANIPULATION OF W-CLASS ENTANGLED STATES: APPLICATIONS TO QUANTUM-INFORMATION PROCESSING

We propose a cavity-quantum-electrodynamics scheme for one-step generation of the special configuration of W-class state [Formula: see text] which can implement deterministic teleportation, superdense coding, quantum-information splitting, and phase-covariant telecloning. We also present a method for one-step realization of a nontrivial unitary transformation [Formula: see text] which can transform a standard W state into a fully separable state. The [Formula: see text] operation plays a key role in recently proposed quantum-information processing tasks. Both the schemes are robust against decoherence. In addition, they can endure the error of controlling the interaction time between atoms and cavity. Our ideas can also be generalized to other systems.

A SCHEME FOR IMPLEMENTATION OF DENSE CODING WITH W-CLASS STATES IN CAVITY QED

An experimentally feasible scheme for implementing quantum dense coding in cavity QED is proposed. In the scheme a W-class state can first be prepared by letting the atoms interact simultaneously with a highly detuned cavity mode. Then the states coded on this W-class state can be exactly distinguished by detecting atomic states. The scheme is insensitive to the cavity field, and the quantum dense coding can be realized in a simple way.

Generalized W-class state and its monogamy relation

We generalize the W-class of states from n-qubits to n-qudits and prove that their entanglement is fully characterized by their partial entanglements even for the case of the mixture that consists of a W-class state and a product state .

Scheme for Implementing Perfect Quantum Teleportation with Non-maximally Entangled W-Class State in Cavity QED

We propose an experimentally feasible teleportation scheme with three-atom W-class state, which was first proposed by Agrawal and Pati [P. Agrawal and A. Pati, Phys. Rev. A 74 (2006) 062320], in cavity QED. In this scheme atoms interact simultaneously with a nonresonant cavity and there is no energy exchange between the atoms and the cavity. Thus it is insensitive to the cavity decay, which is of importance in view of experiment.

Random-party entanglement distillation in multiparty states

We describe various results related to the random-party distillation of multiparty entangled states---that is, conversion of such states into entangled states shared between fewer parties, where those parties are not predetermined. In previous work we showed that certain output states (namely Einstein-Podolsky-Rosen pairs) could be reliably acquired from a prescribed initial multipartite state [namely the W state $|\text{W}⟩=\frac{1}{\sqrt{3}}(|100⟩+|010⟩+|001⟩)$] via random-party distillation that could not be reliably created between predetermined parties. Here we provide a more rigorous definition of what constitutes ``advantageous'' random-party distillation. We show that random-party distillation is always advantageous for W-class three-qubit states (but only sometimes for Greenberger-Horne-Zeilinger class states). We show that the general class of multiparty states known as symmetric Dicke states can be readily converted to many other states in the class via random-party distillation. Finally we show that random-party distillation is provably not advantageous in the limit of multiple copies of pure states.

Scheme for implementing perfect remote state preparation with W-class state in cavity QED

In this paper we present a remote state preparation scheme with a three-qubit W-class state in cavity QED. It has been shown that a special single-qubit state and a special two-qubit entangled state can be remotely prepared perfectly. Furthermore, the classical information cost in this scheme is less than that in the corresponding teleportation scheme and only a single-qubit projective measurement is made by the sender. We also generalize this idea to the multiqubit W-class state.

Distillation of GHZ State from Multiple Copies of Arbitrary W-Class State

W. Dür et al. have shown that it is impossible to obtain a GHZ state from one copy of arbitrary W-class state via local operations and classical communication (LOCC) [W. Dür, G. Vidal, and J.I. Cirac, Phys. Rev. A 62 (2000) 062314]. In our paper, the more general case is carefully investigated. We first show that, with a supply of two copies of arbitrary W-class state, we can always construct an explicit procedure to distill a GHZ state with a nonzero probability. Then based on this result, a simple procedure for distilling GHZ state from n copies of arbitrary W-class state is presented. Finally, we briefly discuss the applications.

Quantum Information Splitting Based on Current Cavity QED Techniques

We propose two schemes for quantum information splitting via W-class state. The first scheme is based on the interaction of single atom with single-mode field, while the second scheme is based on the simultaneous interaction of two atoms with single-mode cavity. For the first scheme, the difficulty of two atoms required to be simultaneously sent through one cavity is avoid. For the second scheme, it is immune to thermal field. Both schemes are experimentally feasible based on current cavity QED techniques.

Scheme for implementing quantum dense coding with W-class state in cavity QED

An experimentally feasible protocol for realizing dense coding by using a class of W-state in cavity quantum electrodynamics (QED) is proposed in this paper. The prominent advantage of our scheme is that the successful probability of the dense coding with a W-class state can reach 1. In addition, the scheme can be implemented by the present cavity QED techniques.

Quantum Teleportation and Superdense Coding via W-Class States

According to the protocol of Agrawal et al., we propose a cavity QED scheme for realization of teleportation and dense coding. Instead of using EPR states and GHZ states, our scheme is more insensitive to the loss of one particle by using a W-class state as a quantum channel. Besides, our scheme is immune to thermal field, and does not require the cavity to remain in the vacuum state throughout the procedure.

Scheme for implementing efficient quantum information processing with multiqubit W-class states in cavity QED

We present a new class of multiqubit W states, which are useful for efficient quantum information processing. By using these states we propose schemes of quantum teleportation, dense coding and information splitting. We also discuss the preparation and detection of the multiqubit W states.

Scheme for implementing perfect quantum dense coding with three-atom W-class state in cavity QED

We propose an experimentally feasible scheme of implementing perfect quantum dense coding with three-atom W-class state in cavity QED. In this scheme atoms interact simultaneously with a highly detuned cavity field and the cavity is only virtually excited, thus the scheme is insensitive to the cavity decay, which is very important in view of experiment. Moreover, we also propose a scheme of transmitting three bits of classical information by sending one qubit and one classical bit with 3-qubit W-class and GHZ states.

Probabilistic generalized controlled order rearrangement encryption and secret splitting using W-class state

Based on the controlled order rearrange encryption (CORE) for quantum key distribution using EPR pairs [Fu.G. Deng, G.L. Long, Phys. Rev. A 68 (2003) 042315], we propose a generalized controlled order rearrangement encryption (GCORE) protocol using non-maximally entangled W-class states with probability, but it also has full efficiency and we compare the similarity and difference with original protocol. Besides, we use this W-class state to split quantum information, thus the scheme is robust against decoherence.

THE GEOMETRIC MEASURE OF ENTANGLEMENT OF THREE-PARTITE PURE STATES

As a measure of entanglement of three-partite pure state, the distance between this state and a set of fully disentangled states is considered. This distance can be calculated for W-class three-qubit pure states and generalized GHZ-states in explicit analytical form. For general multipartite pure states, the distance up to the set of 1-disentangled states is derived. This value can be considered as a low bound for the entanglement of multipartite pure state.

Controlled Implementation of Non-local CNOT Operation UsingThree-Qubit Entanglement

We investigate the controlled implementation of a non-local CNOT operationusing a three-qubit entangled state. Firstly, we show how the non-local CNOToperation can be implemented with unit fidelity and unit probability byusing a maximally entangled GHZ state as controlled quantum channel. Then,we put forward two schemes for conclusively implementing the non-localoperation with unit fidelity by employing a partially entangled pure GHZstate as quantum channel. The feature of these schemes is that a thirdside is included, who may participate the process of quantum non-localimplementation as a supervisor. Furthermore, when the quantum channel ispartially entangled, the third one can rectify the state distorted byimperfect quantum channel. In addition to the GHZ class state, the W classstate can also be used to implement the same non-local operationprobabilistically. The probability of successful implementation using the Wclass state is always less than that using the GHZ class state.

SU(3) Symmetry Operational Approach to Measuring Amplitude and Phase Parameters for an Optical Field

We consider a new approach to the SU(3) symmetry polarization in Hilbert space for a quantum-optical Bose system with internal Gell-Mann symmetry. The operational determination of the SU(3) amplitude and phase characteristics for a three-mode optical field is discussed for the first time. An original twelve-port interferometer for simultaneous measurements of both the Gell-Mann and the phase parameters is proposed. The quantum properties of various W-class qutrit states under the measurement procedure for quantum information purposes are examined.

Entangled States of Atoms upon Interaction with Narrowband Light

The process of resonant interaction of light with two-level atoms in the absence of relaxation is considered. For a special form of initial conditions, simple and exact solutions are found that describe coherent processes leading to the appearance of many-particle entangled W-class states. These processes can be used for preparation and transformation of entangled states, in particular, for problems of quantum memory and generation of entangled atomic chains.