Narrow Results

The standard quantum teleportation scheme is deconstructed, and those aspects of it that appear remarkable and “non classical” are identified. An alternative teleportation scheme, involving only classical states and classical information, is then formulated, and it is shown that the classical scheme reproduces all of these remarkable aspects, despite the fact that they had seemed non classical. This leads to a re examination of quantum teleportation, which suggests that its significance depends on the interpretation of quantum states.

In response to a recently published protocol for classical teleportation of classical states [1], Hrasko [2] has made some remarks in connection with the impossibility of precise quantum teleportation if a classical mixture is used in place of the EPR state, and with regard to the epistemological interpretation of quantum states. The purpose of this note is to attempt to clarify these issues and their relevance for the argumentation presented in [1].

We investigate controlled quantum teleportation of an arbitrary entangled state. It is shown [Man et al., J. Phys. B 40 (2007) 1767] that by using EPR and GHZ states, an unknown N-qubit entangled state can be teleported from a sender to a receiver, under control of a third party. This protocol is studied in more details in our work. The protocol is simulated for a small number of qubits. It is found that a W state, instead of the GHZ state, should be used for a successful teleportation of an entangled state. The difference between the initial state to be teleported and the final state reproduced is studied for different amount of entanglement of the W-like state.

We review the working principle of a liquid-state Nuclear Magnetic Resonance (NMR) quantum computer where spins of nuclei in isolated molecules dissolved in a solvent work as qubits and they are controlled by radio frequency magnetic field pulses. Then, we show some of our recent experimental results, "generation and suppression of artificial decoherence" and "quantum teleportation without irreversible detection".

Non-Markovian dynamics of quantum entanglement and teleportation process with continuous variables carried by accelerated observers under the influence of the environment is studied. In the full time nonperturbative evolution of quantum entanglement, the environment is found to play a dual role: It creates multipartite entanglement among observers, while suppressing them via decoherence. Motivated by the black hole information problem, we consider quantum teleportation between static and accelerated observers. Acceleration of the observer suppresses fidelity of teleportation. Information can escape outside of the horizon in the form of bipartite and tripartite entanglement during the teleportation process. Time dependence of information loss is calculated. In addition to the loss due to the interaction with the environment, the intrinsic loss in a measurement process was analysed.