Network controlled teleportation of N-qubit state

By employing the tensor analysis technique, we propose three schemes of controlled teleportation: series controlled, circular controlled and network controlled teleportation. We discuss the necessary and sufficient condition for realizing these schemes, in which we use a general two-qubit entangled state instead of the GHZ state as the communication channel. This enables successful implementation of teleportation without using the Hadamard operation.     

Quantum teleportation with a complete Bell state measurement

By using the quantum teleportation protocol, Alice can send an unknown quantum state (e.g. the polarization of a single photon) to Bob without ever knowing about it. This paper discusses a quantum teleportation experiment in which nonlinear interactions are used for the Bell state measurement. Since the Bell state measurement is based on nonlinear interactions, all four Bell states can be distinguished. Therefore, teleportation of a polarization state can occur with certainty, in principle. Details of the theory and the experimental set-up are discussed.     

Partial teleportation of entanglement in a noisy environment

Abstract

Partial teleportation of entanglement is to teleport one particle of an entangled pair through a quantum channel. This is conceptually equivalent to quantum swapping. We consider the partial teleportation of entanglement in the noisy environment, employing the Werner-state representation of the noisy channel for the simplicity of calculation. To have the insight of the many-body teleportation, we introduce the measure of correlation information and study the transfer of the correlation information and entanglement. We find that the fidelity becomes smaller as the initial state is entangled more for a given entanglement of the quantum channel. The entangled channel transfers at least some of the entanglement to the final state.     

Long-distance teleportation based on a selected receiver in a quantum network

Quantum networks are useful for global communication. A new multi-hop scheme of single unitary transformation method (SUTM) is proposed for long-distance teleportation of an unknown W state in a quantum network. All the measurement outcomes are sent to the selected receiver independently. The initial quantum state can be recovered by a corresponding local operation. The probability of successful teleportation can reach 1 without auxiliary particles. Our scheme is superior to the hop-by-hop method owing to lower delays.     

Generation of multiphoton Greenberger–Horne–Zeilinger state and its two kinds of teleportation

We propose a comprehensive experimental scheme to generate and teleport GHZ states of any number of photons as well as to accomplish the process of open-destination teleportation of a single photon's arbitrary state. The equipment and techniques which are used in our scheme are all feasible under current technology. Moreover, we make a direct extension of the above cases and investigate the open-destination teleportation of any M-photon general GHZ states with a brief diagram.     

Teleportation of the states of motion of atoms by interaction with two-slit screens and cavities

We present a scheme of teleportation of the state of motion of atoms, making use of screens with slits and cavities. The fascinating aspects of quantum mechanics are highlighted, utilizing entanglement and the interaction of atoms with slits.     

Wigner representation for entanglement swapping using parametric down conversion: the role of vacuum fluctuations in teleportation

We apply the Wigner formalism of quantum optics in the Heisenberg picture to study the role of the zeropoint field fluctuations in entanglement swapping produced via parametric down conversion. It is shown that the generation of mode entanglement between two initially non-interacting photons is related to the quadruple correlation properties of the electromagnetic field, through the stochastic properties of the vacuum. The relationship between the process of transferring entanglement and the different zeropoint inputs at the non-linear crystal and the Bell-state analyser is emphasized.     

Quadrature operators with arbitrary phase and applications to phase-space distribution and quantum communication

Quadrature operators with arbitrary phase are studied from a point of view of the phase-space representation of quantum states, and the results are applied to simultaneous measurement and quantum communication. The Wigner function of arbitrary phase quadrature variables is introduced, which is a generalization of the usual Wigner function of position and momentum. The Kirkwood distribution is also extended for arbitrary phase quadrature variables. The simultaneous measurement of two quadrature operators is investigated using a beam splitter model and a generalized version of the Arthurs-Kelley model. The quantum teleportation of continuous variables is considered in terms of arbitrary phase quadrature variables. A general formula is derived that provides the quantum teleportation channel. The fidelity of the quantum teleportation with an uncontrollable phase is calculated for a coherent state. Furthermore, the mutual information of the quantum dense coding of continuous variables is obtained when classical information is encoded on arbitrary phase quadrature variables. The result is compared with that of the communication system, where information is transmitted using coherent and squeezed states.     

Electrical and optical control of entanglement entropy in a coupled triple quantum dot system

We investigated theoretically the entanglement creation through tunneling rate and fields in a four-level triple quantum dot molecule based on InAs/GaAs/AlGaAs heterostructure in both steady state and transient state. We demonstrate that the entanglement entropy among the QDM and its spontaneous emission fields can be controlled by coherent and incoherent pumping field and tunnel-coupled electronics levels. The results may provide some new possibilities for technological applications in solid-state quantum information science, quantum computing, teleportation, encryption, compression codec, and optoelectronics.     

A general method of controlled bidirectional quantum teleportation of qudit state

Based on tensor representation and d-dimensional Bell basis measurements, we obtained a necessary condition for realizing controlled bidirectional quantum teleportation of qudit states. To verify its theoretical feasibility, we further give a general and simple method of selecting quantum channels for teleporting the ququart state.     

Proposal for optical parity state re-encoder

We propose a re-encoder to generate a refreshed parity encoded state from an existing parity encoded state. This is the simplest case of the scheme by Gilchrist et al. [Phys. Rev. A 2007 75, 052328]. We give a detailed experimental arrangement for the re-encoder and show that it is possible to experimentally demonstrate with existing technology parity encoded quantum gates and teleportation.     

Entanglement and quantum teleportation with multi-atom ensembles

Atomic ensembles containing a large number of atoms have been proved to be an effective medium for quantum-state (quantum information) engineering and processing via their coupling with multi-photon light pulses. The general mechanism of this coupling, which involves continuous quantum variables for light and atoms, is described. The efficient quantum interface between light and atoms has led to the recent demonstration of an entangled state of two macroscopic atomic objects, more precisely two caesium gas samples. Based on this result, a proposal for teleportation of an entangled state of two atomic samples (entanglement swapping) is presented.     

Perfect Quantum Teleportation via Bell States

Quantum mechanics shows superiority than classical mechanics in many aspects and quantum entanglement plays an essential role in information processing and some computational tasks such as quantum teleportation (QT). QT was proposed to transmit the unknown states, in which EPR pairs, the entangled states, can be used as quantum channels. In this paper, we present two simple schemes for teleporting a product state of two arbitrary single-particle and an arbitrary two-particle pure entangled state respectively. Alice and Bob have shared an entangle state. Two Bell states are used as quantum channels. Then after Alice measuring her qubits and informing Bob her measurement results, Bob can perfectly reconstruct the original state by performing corresponding unitary operators on his qubits. It shown that a product state of two arbitrary single-particle and an arbitrary two-particle pure entangled state can be teleported perfectly, i.e. the success probabilities of our schemes are both 1.     

Hyper-entangled states

Abstract

Entangled states are key ingredients to the new field of quantum information, including quantum dense coding, teleportation, and computation. However, only a relatively small class of entangled states has been investigated experimentally, or even discussed extensively. In particular, efforts to date have focused on two particles entangled in a single degree of freedom, for example polarization, or energy, or momentum direction. Novel phase-matching arrangements in spontaneous parametric down-conversion allow the preparation of pairs of photons that are simultaneously entangled in all of these. We shall call such a multiply-entangled state ?hyper-entangled‘. In addition, an even more general state–-a non-maximally entangled state–-should be realizable, in which the amplitudes of the contributing terms are not equal.     

Biased EPR entanglement and its application to teleportation

Abstract

We consider pure continuous variable entanglement with nonequal correlations between orthogonal quadratures. We introduce a simple protocol which equates these correlations and in the process transforms the entanglement onto a state with the minimum allowed number of photons. As an example we show that our protocol transforms, through unitary local operations, a single squeezed beam split on a beam splitter into the same entanglement that is produced when two squeezed beams are mixed orthogonally. We demonstrate that this technique can in principle facilitate perfect teleportation utilizing only one squeezed beam.     

Comment: There is no unmet requirement of optical coherence for continuous-variable quantum teleportation

Abstract

It has been argued that continuous-variable quantum teleportation at optical frequencies has not been achieved because the source used (a laser) was not ‘truly coherent’. Here it is shown that ‘true coherence’ is always illusory, as the concept of absolute time on a scale beyond direct human experience is meaningless. A laser is as good a clock as any other, even in principle, and this objection to teleportation experiments is baseless.     

The signal recovery of continuous variable quantum communication system

In this paper, a novel continuous variable quantum teleportation (CVQTS) scheme based on quantum neural network (QNN) is proposed to implement the high-efficient and communication security. To achieve the teleportation in two-dimensional Hilbert space, the continuous variable quantum states are split into N modes by an array of N ? 1 beam splitters (N-splitter) in the continuous variable quantum teleportation channel (CVQTC). The QNN is applied to trace and restore the distortion signals. It used QNN training indirectly to obtain the weight parameters. In order to ensure the communication security, only a small number of information is extracted as training expectation. The results demonstrate that our scheme is capable of enhancing the fidelity close to 1 for almost all teleported information. Due to the simple structure of QNN, CVQTS scheme based on QNN can be applied to any other inputs and improves the maneuverability and realizability in the experiment.     

21世纪电子学的若干前沿课题

文章讨论了进入21世纪时物理学和电子学的现状和若干前沿课题,涉及真空能、电子负质量、量子势、虚粒子、超弦理论、快子,以及EPR思维实验、量子交缠与量子远距传物、量子信息学、量子计算机等方面的最新研究进展与成果。     

Perfect transmission of the sub-poissonian character of a field via continuous-variable teleportation

Abstract

We optimize the transmission of quantum features in light fields, such as squeezing and antibunching, using continuous variable teleportation and tuning the variable gain in Bob's output.     

Scheme for the generation of entangled solitons for quantum communication

Abstract

Quantum-communication needs a source of entanglement which is accessible to non-local measurements. It is shown that an entangled pair of light beams may be generated from two bright amplitude squeezed beams. This is applicable to light pulses and to optical solitons in fibres. A possible experimental scheme for stroboscopic quantum teleportation is discussed.