Showing papers on "No-teleportation theorem published in 1997"

Experimental quantum teleportation

Abstract: Quantum teleportation — the transmission and reconstruction over arbitrary distances of the state of a quantum system — is demonstrated experimentally. During teleportation, an initial photon which carries the polarization that is to be transferred and one of a pair of entangled photons are subjected to a measurement such that the second photon of the entangled pair acquires the polarization of the initial photon. This latter photon can be arbitrarily far away from the initial one. Quantum teleportation will be a critical ingredient for quantum computation networks.

Sending classical information via noisy quantum channels

Abstract: This paper extends previous results about the classical information capacity of a noiseless quantum-mechanical communication channel to situations in which the final signal states are mixed states, that is, to channels with noise.

Substituting quantum entanglement for communication

Abstract: We show that quantum entanglement can be used as a substitute for communication when the goal is to compute a function whose input data are distributed among remote parties. Specifically, we show that, for a particular function among three parties (each of which possesses part of the function's input), a prior quantum entanglement enables one of them to learn the value of the function with only two bits of communication occurring among the parties, whereas, without quantum entanglement, three bits of communication are necessary. This result contrasts the well-known fact that quantum entanglement cannot be used to simulate communication among remote parties.

Information-theoretic interpretation of quantum error-correcting codes

Abstract: Quantum error-correcting codes are analyzed from an information-theoretic perspective centered on quantum conditional and mutual entropies. This approach parallels the description of classical error correction in Shannon theory, while clarifying the differences between classical and quantum codes. More specifically, it is shown how quantum information theory accounts for the fact that “redundant” information can be distributed over quantum bits even though this does not violate the quantum “no-cloning” theorem. Such a remarkable feature, which has no counterpart for classical codes, is related to the property that the ternary mutual entropy vanishes for a tripartite system in a pure state. This information-theoretic description of quantum coding is used to derive the quantum analog of the Singleton bound on the number of logical bits that can be preserved by a code of fixed length which can recover a given number of errors.

Quantum teleportation and the non-locality of information

Abstract: A two–state quantum system (a qubit) can carry one bit of classical information. If two bits are not encoded into two qubits separately, but only into their joint properties, entangled states result. It is shown explicitly how quantum teleportation utilizes this feature and how the randomness of the individual quantum event prohibits instantaneous communication.

Scheme for reducing decoherence in quantum computer memory by transformation to the coherence-preserving states

Abstract: If quantum bits (qubits) couple to the same environment, it has been found the qubits decohere coherently. An interesting result from this phenomenon is that, for a kind of input states, i.e., the coherence-preserving states, coherence of the qubits can be preserved perfectly in quantum memory. In this paper, we propose a feasible scheme to transform an arbitrary unknown input state to the corresponding coherence-preserving state. The transformed state undergoes no decoherence in the noisy memory and, after that, it can be transformed back into the original state with decoherence much reduced. This scheme involves the use of an analogy of the ideas of quantum teleportation.