No Arabic abstract
We propose a modified protocol of atomic state teleportation for the scheme proposed by Bose et al. (Phys. Rev. Lett. 83, 5158 (1999)). The modified protocol involves an additional stage in which quantum information distorted during the first stage is fully recovered by a compensation of the damping factor. The modification makes it possible to obtain a high fidelity of teleported state for cavities that are much worse than that required in the original protocol, i.e., their decay rates can be over 25 times larger. The improvement in the fidelity is possible at the expense of lowering the probability of success. We show that the modified protocol is robust against dark counts.
We propose a scheme to teleport an entangled state of two $Lambda$-type three-level atoms via photons. The teleportation protocol involves the local redundant encoding protecting the initial entangled state and allowing for repeating the detection until quantum information transfer is successful. We also show how to manipulate a state of many $Lambda$-type atoms trapped in a cavity.
We propose a protocol of the long-distance atomic state teleportation via cavity decay, which allows for high-fidelity teleportation even with currently available optical cavities. The protocol is based on the scheme proposed by Bose emph{et al.} [Phys. Rev. Lett. {textbf{83}}, 5158 (1999)] but with one important modification: it employs non-maximally-entangled states instead of maximally entangled states.
We present a physical scheme for entanglement concentration of unknown atomic entangled states via cavity decay. In the scheme, the atomic state is used as stationary qubit and photonic state as flying qubit, and a close maximally entangled state can be obtained from pairs of partially entangled states probabilistically.
We employ the technique of weak measurement in order to enable preservation of teleportation fidelity for two-qubit noisy channels. We consider one or both qubits of a maximally entangled state to undergo amplitude damping, and show that the application of weak measurement and a subsequent reverse operation could lead to a fidelity greater than $2/3$ for any value of the decoherence parameter. The success probability of the protocol decreases with the strength of weak measurement, and is lower when both the qubits are affected by decoherence. Finally, our protocol is shown to work for the Werner state too.
We propose a protocol to achieve high fidelity quantum state teleportation of a macroscopic atomic ensemble using a pair of quantum-correlated atomic ensembles. We show how to prepare this pair of ensembles using quasiperfect quantum state transfer processes between light and atoms. Our protocol relies on optical joint measurements of the atomic ensemble states and magnetic feedback reconstruction.