Showing papers on "No-teleportation theorem published in 1999"

Quantum secret sharing

Abstract: Secret sharing is a procedure for splitting a message into several parts so that no subset of parts is sufficient to read the message, but the entire set is. We show how this procedure can be implemented using Greenberger-Horne-Zeilinger (GHZ) states. In the quantum case the presence of an eavesdropper will introduce errors so that his presence can be detected. We also show how GHZ states can be used to split quantum information into two parts so that both parts are necessary to reconstruct the original qubit.

Cost of Exactly Simulating Quantum Entanglement with Classical Communication

Abstract: We investigate the amount of communication that must augment classical local hidden variable models in order to simulate the behavior of entangled quantum systems. We consider the scenario where a bipartite measurement is given from a set of possibilities and the goal is to obtain exactly the same correlations that arise when the actual quantum system is measured. We show that, in the case of a single pair of qubits in a Bell state, a constant number of bits of communication is always sufficient---regardless of the number of measurements under consideration. We also show that, in the case of a system of $n$ Bell states, a constant times ${2}^{n}$ bits of communication is necessary.

Disentangling Nonlocality and Teleportation

Abstract: Quantum entanglement can be used to demonstrate nonlocality and to teleport a quantum state from one place to another. The fact that entanglement can be used to do both these things has led people to believe that teleportation is a nonlocal effect. In this paper it is shown that teleportation is conceptually independent of nonlocality. This is done by constructing a toy local theory in which cloning is not possible (without a no-cloning theory teleportation makes limited sense) but teleportation is. Teleportation in this local theory is achieved in an analogous way to the way it is done with quantum theory. This work provides some insight into what type of process teleportation is.

Quantum State Teleportation Understood Through the Bohm Interpretation

Abstract: Quantum state teleportation has focused attention on the role of quantum information. Here we examine quantum teleportation through the Bohm interpretation. This interpretation introduced the notion of active information and we show that it is this information that is exchanged during teleportation. We discuss the relation between our notion of active information and the notion of quantum information introduced by Schumacher.

Active Information and Teleportation

Abstract: In this paper I want to examine quantum teleportation (Bennett et al. 1993, Bouwmeester et al. 1997) from a point of view that is different from that normally considered. This will enable us to gain a new perspective into what is involved in the process of teleportation. It is clear that, at least in the case where particles are involved, it is not the particle that is transported, but rather the information contained in the wave function. This idea in itself is not new, but the central question that requires clarification is the nature of this information. This paper provides a new insight into this question.

On the Teleportation of Continuous Variable

Abstract: The measurement procedures used in quantum teleportation are analyzed from the viewpoint of the general theory of quantum-mechanical measurements. It is shown that to find the teleported state one should only know the identity resolution (positive operator-valued measure) generated by the corresponding instrument (quantum operation describing the system state change caused by the measurement) rather than the instrument itself. A quantum teleportation protocol based on a measurement associated with a non-orthogonal identity resolution is proposed for a system with non-degenerate continuous spectrum.

Entanglement teleportation

Abstract: Summary form only given. Quantum teleportation is a transportation process of a quantum state where the quantum state is copied at a remote place while the original state id eliminated. We generalize the scheme of the quantum teleportation for "N-body" quantum states. Many-body quantum states are classified into uncorrelated and entangled states. An uncorrelated state can be factorized to the direct product of one-body states. The quantum teleportation of the uncorrelated state can be performed by teleporting its "one-body" states sequentially. Thus, teleporting uncorrelated states is trivial since it is practically equivalent to teleporting one body states. An entangled state, to the contrary, can not be factorized to the product of one-body states due to its entanglement.

A role of antiquantum bits for superdense coding and quantum computing

Abstract: We define an anti-quantum bit state via analogous way as the anti-state in Particle PhysicsWe show the quantum information Feymann diagrams for the teleportations and superdense coding, which preserve the information flow The role of information vacuum and anihilation between error information and anti-information is mentioned for the stability of quantum computing

Enhanced information capacity in dense coding quantum communication

Abstract: Dense coding is a new concept of quantum communication using the nonlocal feature of quantum entangled states. Bob, the information receiver, prepares polarization-entangled photon twins and sends one of them to Alice, the information sender, while retaining the other. She can prepare each of the four Bell states by operating an appropriate manipulation only on the transmitted photon and thus she can encode 2 bits of information. To decode the 2 bits, Bob must execute a joint measurement of the returned and retained photons with a Bell-state analyzer, such as a Hong-Ou-Mandel type of two-photon interferometer. The information capacity of the transmitted photon is limited by the number of usable nonlocal quantum states which can be prepared through the local operation on one photon. A question arises as to whether Alice can enhance the capacity or not, by adopting an additional degree of freedom by use of pulse position modulation or optical frequency modulation for the transmitted photon. At a glance, capacity enhancement appears to be possible by introducing another degree of freedom. The question here is, however, whether or not it is possible by manipulating only one of photon twins. In the paper, however, we show that the information capacity in dense coding can be enhanced from the reported 2 bits to 3 bits provided that photon twins have spectral correlation and a perfect Bell state analyzer is available.