Generation of hyperentangled four-photon cluster state via cross-Kerr nonlinearity

We propose a scheme for generating a hyperentangled four-photon cluster state that is simultaneously entangled in polarization modes and spatial modes. This scheme is based on linear optical elements, weak cross-Kerr nonlinearity, and homodyne detection. Therefore, it is feasible with current experimental technology.     

Effective protocol for preparation of three-atom Greenberger-Horne-Zeilinger state and W state with the help of cross-Kerr nonlinearity

We propose a protocol to generate a Greenberger-Horne-Zeilinger (GHZ) state andWstate by using simple linear elements and quantum nondemolition detectors (QNDs). With the help of cross-Kerr nonlinearity, our protocol can generate the intended states with only one setup, and the probability of getting a W state is greatly increased when compared with previous schemes [Phys. Rev. A 75 (2007) 044301]. Also, our proposed protocol is realizable in experiments.     

Efficient preparation of a four-photon cluster state with homodyne measurement via cross-Kerr nonlinearity

A scheme is proposed for generating a multiphoton entangled cluster state among four modes. The scheme only uses Kerr medium, beam splitter and homodyne measurements on coherent light fields, which can be efficiently made in quantum optical laboratories. The photon in the signal mode is prepared in a superposition state of the vacuum state and one-photon state while the probe beam is initially set in a coherent state superposition. The strong probe mode interacts successively with multiple signal-mode photo...     

Robust scheme for the preparation of symmetric Dicke states with coherence state via cross-Kerr nonlinearity

A scheme is proposed for generating multiphoton maximally entangled states among four modes. These schemes only use Kerr medium and polarization beam splitters and P homodyne measurements on coherent light fields, which can be efficiently implemented in quantum optical laboratories. It's comparatively easy to realize symmetric Dicke state of light fields in the scheme. The scheme can be generalized to produce N-qubit maximally entangled states.     

Efficient W polarization state distribution over an arbitrary collective-noise channel with cross-Kerr nonlinearity

We propose an efficient protocol for W polarization entangled state distribution over an arbitrary collective-noise channel with the help of the cross-Kerr nonlinearity. The entangled state in the frequency degree of freedom, which suffers little from the noise in an optical fiber, is used in the present protocol. The frequency entanglement can be transferred into polarization entanglement with the success probability of 100%. So, the three parities can share the maximally W polarization state with local operations and polarization independent wavelength division multiplexers which can erase distinguishability for frequency.     

Complete four-photon cluster-state analyzer based on cross-Kerr nonlinearity

We propose a method to construct an optical cluster-state analyzer based on cross-Kerr nonlinearity combined with linear optics elements. In the scheme, we employ two four-qubit parity gates and the controlled phase gate （CPG） from only the cross-Kerr nonlinearity and show that all the orthogonal four-qubit cluster states can be completely identified. The scheme is significant for the large-scale quantum communication and quantum information processing networks. In addition, the scheme is feasible and deterministic under current experimental conditions.     

Robust schemes for the generation of multipartite entanglement for remote atoms with cross-Kerr nonlinearity

Based on the interference effect of indistinguishable polarized photons leaking out of separated cavities with each atom trapped in separate cavity, using quantum nondemolition detection, we propose the robust schemes for the generation of N-atom GHZ state, three-atom W state and four-atom cluster state with a certain success probability. In Lamb-Dicke limit, the schemes do not require the simultaneous click of the photon-detectors. These made the schemes more realizable in experiments. Meanwhile, the advantage of the scheme is that the fidelity of the entangled states is not affected by the atomic spontaneous, cavity decay, and imperfection of the photodetectors. The schemes would be useful steps towards long-distance quantum communication.     

Deterministic nonlinearity in ventricular fibrillation

We provide numerical evidence that the electrocardiogram data collected from pigs during induced ventricular fibrillation cannot be described by a monotonic nonlinear transformation of linearly filtered noise. To establish this we use surrogate techniques and apply two test statistics: (1) the Takens' maximum likelihood estimator of the Grassberger-Procaccia correlation dimension and (2) an improved correlation dimension estimation routine. The improved dimension estimates provide evidence that the correlation dimension of the underlying dynamics during the episode of VF in the first 30 s is slightly less than 6. This result is consistent and reproducible among subjects. (c) 2000 American Institute of Physics.     

Quantum teleportation of an entangled 2-photon polarization state with preparing determinately two Bell states based on cross-Kerr nonlinearity

A scheme, in which cross-Kerr nonlinearity is used for the Bell-state measurements and preparation of the resource of entanglement, is proposed for teleporting an entangled 2-photon state by using two polarization-photon Bell states as quantum channel based on cross-Kerr nonlinearity combined with linear optics elements such as polarization beam splitters and half wave plates. Teleportation of the entangled 2-photon polarization state can realized with certainty in principle.     

Efficient scheme for the preparation of symmetric Dicke states via cross-Kerr nonlinearity

A scheme is proposed for generating maximally entangled Dicke states among four modes. The scheme only uses Kerr medium and homodyne measurements on coherent light fields, which can be efficiently made in quantum optical laboratories. The scheme can be generalized to produce maximally entangled 2k-qubit states.     

Deterministic hierarchical joint remote state preparation with six-particle partially entangled state

In this paper, we present a novel scheme for hierarchical joint remote state preparation(HJRSP) in a deterministic manner, where two senders can jointly and remotely prepare an arbitrary single-qubit at three receivers' port. A six-particle partially entangled state is pre-shared as the quantum channel. There is a hierarchy among the receivers concerning their powers to reconstruct the target state. Due to various unitary operations and projective measurements, the unit success probability can always be achieved irrespective of the parameters of the pre-shared partially entangled state.     

Deterministic joint remote state preparation

We put forward a new nontrivial three-step strategy to execute joint remote state preparation via Einstein-Podolsky-Rosen pairs deterministically. At variance with all existing protocols, in ours the receiver contributes actively in both preparation and reconstruction steps, although he knows nothing about the quantum state to be prepared.     

Quantum secure direct communication network with hyperentanglement

We propose a quantum secure direct communication protocol with entanglement swapping and hyperentanglement.Any two users, Alice and Bob, can communicate with each other in a quantum network, even though there is no direct quantum channel between them. The trust center, Trent, who provides a quantum channel to link them by performing entanglement swapping, cannot eavesdrop on their communication. This protocol provides a high channel capacity because it uses hyperentanglement, which can be generated using a beta barium borate crystal.     

Deterministic quantum dense coding with cluster state in optical systems

We propose two optical schemes for implementing the deterministic single-particle and two-particle quantum dense coding using four-qubit cluster states. In the protocols, the photon is neuter particle, so it has longer decoherence time with the environment than other particles. It is easy to implement single-bit gate using the linear optical elements under certain conditions, so the transformations performed on the photons by Alice can be easily achieved. Here the cluster states can be exactly discriminated using the parity detector, PBS and FS-PBS. In addition, the success probabilities of the dense coding are both equal to 1.     

Bidirectional quantum teleportation of unknown photons using path-polarization intra-particle hybrid entanglement and controlled-unitary gates via cross-Kerr nonlinearity

We propose an arbitrary controlled-unitary(CU) gate and a bidirectional quantum teleportation(BQTP) scheme. The proposed CU gate utilizes photonic qubits(photons) with cross-Kerr nonlinearities(XKNLs), X-homodyne detectors, and linear optical elements, and consists of the consecutive operation of a controlled-path(C-path) gate and a gathering-path(Gpath) gate. It is almost deterministic and feasible with current technology when a strong coherent state and weak XKNLs are employed. Based on the CU gate, we present a BQTP scheme that simultaneously teleports two unknown photons between distant users by transmitting only one photon in a path-polarization intra-particle hybrid entangled state. Consequently, it is possible to experimentally implement BQTP with a certain success probability using the proposed CU gate.     

A nondestructive method for estimation of the fracture toughness of CrMoV rotor steels based on ultrasonic nonlinearity

The objective of this paper is to develop a nondestructive method for estimating the fracture toughness (K(IC)) of CrMoV steels used as the rotor material of steam turbines in power plants. To achieve this objective, a number of CrMoV steel samples were heat-treated, and the fracture appearance transition temperature (FATT) was determined as a function of aging time. Nonlinear ultrasonics was employed as the theoretical basis to explain the harmonic generation in a damaged material, and the nonlinearity parameter of the second harmonic wave was the experimental measure used to be correlated to the fracture toughness of the rotor steel. The nondestructive procedure for estimating the K(IC) consists of two steps. First, the correlations between the nonlinearity parameter and the FATT are sought. The FATT values are then used to estimate K(IC) using the K(IC) versus excess temperature (i.e., T-FATT) correlation that is available in the literature for CrMoV rotor steel.     

Proposal for on-chip generation and control of photon hyperentanglement

An on-chip waveguide-based source of entangled photons capable of switching between generating time-energy entangled and hyperentangled (entangled in both time energy and polarization) photon pairs is proposed. The switching can be done all-optically by rotating the pump polarization. The source is based on multichannel phase matching in Bragg reflection waveguides achieved by engineering the Fresnel reflection of photonic bandgap claddings for differently polarized modes. Analytical results are confirmed in fully vectorial numerical simulations.     

Deterministic quantum communication using the symmetric W state

This study proposes a new coding function for the symmetric W state.Based on the new coding function,a theoretical protocol of deterministic quantum communication(DQC) is proposed.The sender can use the proposed coding function to encode his/her message,and the receiver can perform the imperfect Bell measurement to obtain the sender’s message.In comparison to the existing DQC protocols that also use the W class state,the proposed protocol is more efcient and also more practical within today’s technology.Moreover,the security of this protocol is analyzed to show that any eavesdropper will be detected with a very high probability under both the ideal and the noisy quantum channel.     

Refined hyperentanglement purification of two-photon systems for high-capacity quantum communication with cavity-assisted interaction

Hyperentanglement, defined as the entanglement in multiple degrees of freedom (DOFs) of a photonic quantum system, has attracted much attention recently as it can improve the channel capacity of quantum communication largely. Here we present a refined hyperentanglement purification protocol (hyper-EPP) for two-photon systems in mixed hyperentangled states in both the spatial-mode and polarization DOFs, assisted by cavity quantum electrodynamics. By means of the spatial (polarization) quantum state transfer process, the quantum states that are discarded in the previous hyper-EPPs can be preserved. That is, the spatial (polarization) state of a four-photon system with high fidelity can be transformed into another four-photon system with low fidelity, not disturbing its polarization (spatial) state, which makes this hyper-EPP take the advantage of possessing a higher efficiency.