Abstract
A scheme of teleporting a superposition of coherent states |α〉 and |-α〉 using a 4-partite state, a beam splitter and two phase shifters was proposed by N. Ba An (Phys. Rev. A, 68, 022321, 2003). The author concluded that the probability for successful teleportation is only 1/4 in the limit |α|→∞ and 1/2 in the limit |α|→∞. In this paper it is shown that the author's scheme can be altered slightly so as to obtain an almost perfect teleportation for an appreciable value of |α|^2 . We find the minimum assured fidelity i.e., the minimum fidelity for an arbitrarily chosen information state, which we write MAF in this paper, for different cases. We also discuss the effect of decoherence on teleportation fidelity. We find that if no photons are counted in both final outputs, MAF, is still nonzero except when there is no decoherence and the initial state (the state to be teleported) is even coherent state. For non-zero photon counts, MAF decreases with increase in |α|^2 for low noise. For high noise, however, it increases, attains a maximum value and then decreases with |α|^2. The average fidelity depends appreciably on the initial state for low values of |α|^2 only.
Highlights
Quantum entanglement has generated much interest in many ingenious applications in quantum information science such as quantum teleportation [1,2,3,4], quantum computation [5], quantum dense coding [6], quantum cryptography [7] and quantum telecloning [8] as well as fundamental studies in quantum mechanics related to the Einstein-Podolsky-Rosen (EPR) paradox [9]
We find that if no photons are counted in both final outputs, minimum assured fidelity (MAF), is still nonzero except when there is no decoherence and the initial state is even coherent state
By including four parties, the security of the teleportation increases, as David cannot decipher the original information until and unless he gets the results from all Alice, Bob and Clair
Summary
Quantum entanglement has generated much interest in many ingenious applications in quantum information science such as quantum teleportation [1,2,3,4], quantum computation [5], quantum dense coding [6], quantum cryptography [7] and quantum telecloning [8] as well as fundamental studies in quantum mechanics related to the Einstein-Podolsky-Rosen (EPR) paradox [9]. In a recent paper [10], a new idea of two-way quantum communication called “secure quantum information exchange” (SQIE) is introduced. If there are two arbitrary unknown quantum states I A and IB , initially with Alice and Bob, respectively, SQIE protocol leads to the simultaneous exchange of these states between Alice and Bob with the aid of the special kind of six-qubit entangled (SSE) state and classical assistance of the third party, Charlie. Teleportation of a two-mode entangled coherent state encoded with two-qubit information has been studied in a recent paper [11,12,13,14,15]. Teleportation of an entangled multiparticle state and coherent. Entangled coherent states [23,24] have received much attention in the study of quantum entanglement and quantum teleportation. Both the publications involved teleportation between two parties.
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