Quantum Secure Communication Using a Class of Three-Particle W State

A theoretical scheme of quantum secure communication using a class of three-particle W states is proposed. In the scheme, two communicators may communicate after they test the security of the quantum channel. The receiver can obtain the secret message determinately if the quantum channel is safe. The present scheme can be realized without using teleportation.     

Tripartition of Arbitrary Single-Qubit Information via a Class of Asymmetric Four-Qubit W State

A four-party scheme is put forward for a sender to partition arbitrary single-qubit information among three receivers by utilizing a class of asymmetric four-qubit W state as quantum channels. In the scheme the sender＇s quantum information can be recovered by the three receivers if and only if they collaborate together. Specifically, they collaborate to perform first two different 2-qubit collective unitary operations and then a single-qubit unitary operation. The scheme is symmetric and （3, 3）-threshold with regard to the reconstruction, for any receiver can be assigned to conclusively recover the quantum information with the other two＇s assistances.     

Classical Communication Cost and Probabilistic Remote Preparation of Four-Particle Entangled W State

We present a scheme for probabilistic remote preparation of the four-particle entangled W state by using four partial entangled two-particle states as the quantum channel. In this scheme, if Alice （sender） performs four-particle projective measurements and Bob （receiver） adopts some appropriate unitary operation, the remote state preparation can be successfully realized with certain probability. The classical communication cost is also calculated. However, the success probability of preparation can be increased to 1 for four kinds of special states.     

Teleportation of N-qubit W State without Bell-State Measurement via Selective Resonant Interaction in Cavity QED

We present a scheme in which the N-atom W state is teleported by employing the selective interaction of a cavity field with a driven three-level atom in the A configuration and detecting a single atom in one of the ground states. The long-lived W state is teleported from atom A to atom B when the atoms B and A are sent through a cavity successively and atom A is then detected. The advantage is that the present one does not involve the Bell-state measurement and is robust against the atomic spontaneous emission.     

Three-Party Quantum State Sharing of an Arbitrary Unknown Two-Qubit State Based on Entanglement Swapping and Bell-State Measurements

We propose a scheme for sharing an arbitrary unknown two-qubit state among three parties by using a four-qubit cluster-class state and a Bell state as a quantum channel. With a quantum controlled phase gate （QCPG） operation and a local unitary operation, any one of the two agents has the access to reconstruct the original state if he/she collaborates with the other one, whilst individual agent obtains no information. As all quantum resource can be used to carry the useful information, the intrinsic efficiency of qubits approaches the maximal value. Moreover, the present scheme is more feasible with present-day technique.     

Knotted Picture of Unknown Quantum State in Process of Quantum Teleportation

This paper gives the knotted picture of the unknown quantum state in the process of quantum teleportation and the surgical knotted operations of the unitary operators operated on the teleported quantum state.     

Knotted Picture of Unitary Transformation Applied to Single Particle Quantum State

This paper introduces the unified expression of four Bell bases and uses the composition operation in knot theory to obtain the knotted picture of unitary operators based on Pauli operators, and gives the knotted expressions of 12 inversion relations between the four Bell bases.     

Influence of Noises on Remote State Preparation Using GHZ State

Using a quantum channel consisting of a GHZ state exposed to noisy environment, we investigate how to remotely prepare an entangled state and a qubit state, respectively. By solving the master equation in the Lindblad form, the influence of the various types of noises on the GHZ state is first discussed. Then we use the fidelity to describe how close the remotely prepared state and the initial state are. Our results show that the fidelity is a function of the decoherence rates and the angles of the initial state. It is found that for each of the two RSP schemes, the influence of the noise acting simultaneously in x, y, and z directions on the average fidelity is the strongest while the influence of the noise acting in x or z direction on the average fidelity is relatively weaker.     

A Kind of Atomic Coherent State as a Two-Mode Squeezed State

We find that a kind of atomic coherent state, formed as exp[ ξJ＋-ξJ-]｜00〉,when the SU（2） generators J± are taken as Fan＇s form J＋=（1/2）（α1-α2）（α1-α2）,J-=（1/2）（α1＋α2）（α1＋α2）,and J0=（1/2）（α1α2-α1α2）,is simultaneously a two-mode squeezed state. We analyse this squeezed state＇s physical properites, such as the cross- correlation function, the Wigner function, and its marginal distribution as well as the Husimi function.     

Teleportation of an Arbitrary Two-Particle State via a Single Cluster-Class State

Teleportation of an arbitrary two-qubit state with a single partially entangled state, a four-qubit linear cluster-class state, is studied. The case is more practical than previous ones using maximally entangled states as the quantum channel. In order to realize teleportation, we first construct a cluster-basis of 16 orthonormal cluster states. We show that quantum teleportation can be successfully implemented with a certain probability if the receiver can adopt appropriate unitary transformations after receiving the sender＇s cluster-basis measurement information. In addition, an important conclusion can be obtained that a four-qubit maximally entangled state （cluster state） can be extracted from a single copy of the cluster-class state with the same probability as the teleportation in principle.     

Controlled Remote State Preparation

We present a scheme for remotely preparing a state via the controls of many agents in a network. In the scheme, the agents＇ controls are achieved by utilizing quantum key distribution. Generally, the original state can be restored by the receiver with probability 1/2 if all the agents collaborate. However, for certain type of original states the restoration probability is unit.     

Teleportation of a Bipartite Entangled Coherent State via a Four-Partite Cluster-Type Entangled State

We present an optical scheme to almost completely teleport a bipartite entangled coherent state using a four-partite cluster-type entangled coherent state as quantum channel. The scheme is based on optical elements such as beam splitters, phase shifters, and photon detectors. We also obtain the average fidelity of the teleportation process. It is shown that the average fidelity is quite close to unity if the mean photon number of the coherent state is not too small.     

A study of transition from n-to p-type based on hexagonal WO3 nanorods sensor

Hexagonal WO3 nanorods are fabricated by a facile hydrothermal process at 180 ℃ using sodium tungstate and sodium chloride as starting materials. The morphology, structure, and composition of the prepared nanorods are studied by scanning electron microscopy, X-ray diffraction spectroscopy, and energy dispersive spectroscopy. It is found that the agglomeration of the nanorods is strongly dependent on the PH value of the reaction solution. Uniform and isolated WO3 nanorods with diameters ranging from 100 nm-150 nm and lengths up to several micrometers are obtained at PH = 2.5 and the nanorods are identified as being hexagonal in phase structure. The sensing characteristics of the WO3 nanorod sensor are obtained by measuring the dynamic response to NO2 with concentrations in the range 0.5 ppm-5 ppm and at working temperatures in the range 25 ℃-250 ℃. The obtained WO3 nanorods sensors are found to exhibit opposite sensing behaviors, depending on the working temperature. When being exposed to oxidizing NO2 gas, the WO3 nanorod sensor behaves as an n-type semiconductor as expected when the working temperature is higher than 50 ℃, whereas, it behaves as a p-type semiconductor below 50 ℃. The origin of the n- to p-type transition is correlated with the formation of an inversion layer at the surface of the WO3 nanorod at room temperature. This finding is useful for making new room temperature NO2 sensors based on hexagonal WO3 nanorods.     

Two-Variable Hermite Polynomial Excitation of Two-Mode Squeezed Vacuum State as Squeezed Two-Mode Number State

We find that the squeezed two-mode number state is just a two-variable Hermite polynomial excitation of the two-mode squeezed vacuum state （THPES）. We find that the Wigner function of THPES and its marginal distributions are just related to two-variable Hermite polynomials （or Laguerre polynomials） and that the tomogram of THPES can be expressed by one-mode Hermite polynomial.     

Study of new boson W±1 in the Minimal Higgsless Model at the LHC

The Minimal Higgsless Model predicts the existence of new vector gauge boson W1^±, By the process PP →W1^±qq →W^±Z^0qq, Z^0→ 1^＋1^-, W^±→ qq （1=e,μ; q is hadronized to be jets）, we study the sensitivity of searching for this possible vector gauge boson in the level of generator events of signal and backgrounds, then give integrated luminosity required to discover 5σ signal as a function of W1^± mass. The generator for the signal PP → W1^±qq →W^±Z^0qq at tree level is developed with the Minimal Higgsless Model and then interfaced with PYTHIA for the patton showers and hadronization. The backgrounds are produced with MadGraph and PYTHIA.     

Scheme for Generalized Quantum State Sharing of a Single-Qubit State in Cavity QED

An experimentally feasible scheme for generalized quantum state sharing of an arbitrary unknown single- qubit state in cavity QED is presented. Using a generalized Greenberger-Horne-Zeilinger （GHZ） state as the quantum channel among the three parties, the quantum information （i.e. the single-qubit state） from the sender can be split in such a way that the information can be recovered if and only if both receivers collaborate. Moreover, the scheme is insensitive to both the effects of thermal field and cavity decay.     

Atomic Coherent State, Entangled State and Phase Operator for Studying Interference Between Two Bose-Einstein Condensates

For studying the interference between two Bose-Einstein condensates we introduce the atomic coherentstate （ACS） in the Schwinger bosonic realization along with the phase operator to directly calculate the interference pattern with steady relative phase cos Ф. Eigenstates of the density operator of condensates are classified as ACS is also demonstrated. The entangled state representation is used in some calculations.     

Quantum Dialogue Protocol Using a Class of Three-Photon W States

A theoretical protocol of quantum dialogue is proposed, which uses a class of three-photon W states as quantum channel. After two-step security check, four-bit secret message can be transmitted to each other by transmitting of single photon with the aid of two-bit classical information.     

Nonequilibrium work equalities in isolated quantum systems

We briefly introduce the quantum Jarzynski and Bochkov–Kuzovlev equalities in isolated quantum Hamiltonian systems, including their origin, their derivations using a quantum Feynman–Kac formula, the quantum Crooks equality, the evolution equations governing the characteristic functions of the probability density functions for the quantum work, and recent experimental verifications. Some results are given here for the first time. We particularly emphasize the formally structural consistence between these quantum equalities and their classical counterparts, which are useful for understanding the existing equalities and pursuing new fluctuation relations in other complex quantum systems.     

On Superconductivity State in Pure Graphene

We study theoretically the possibility of superconductivity state in pure graphene within the extended attractive Hubbard model. In the absence of disorder, when we use the local attractive interaction potential, U ≌ 5t, where t is hopping term, pure graphene can be in superconductivity state.