Quantum Teleportation of N qubits with perfect fidelity using maximally entangled states is explained. It is shown that non-maximally entangled states are used the minimum assured fidelity decreases. It is explained how the success 1/2 of teleportation of a superposition of even and odd coherent states suggested by Van Enk and Hirota was modified by Prakash, Chandra, Prakash and Shivani. It is also shown that the decrease in entanglement may sometimes even result in increase in fidelity. so as to make the success nearly 1. It is also explained how decoherence can be taken into account and how such schemes can be applied to similar phenomena of entanglement diversion and entanglement swapping.
Quantum Teleportation of N qubits with perfect fidelity using maximally entangled states is explained. It is shown that non-maximally entangled states are used the minimum assured fidelity decreases. It is explained how the success 1/2 of teleportation of a superposition of even and odd coherent states suggested by Van Enk and Hirota was modified by Prakash, Chandra, Prakash and Shivani. It is also shown that the decrease in entanglement may sometimes even result in increase in fidelity. so as to make the success nearly 1. It is also explained how decoherence can be taken into account and how such schemes can be applied to similar phenomena of entanglement diversion and entanglement swapping.
A scheme of teleporting a superposition of coherent states |α⟩ and | − α⟩ using a beam splitter and two phase shifters was proposed by van Enk and Hirota (2001 Phys. Rev. A 64 022313). The authors concluded that the probability for successful teleportation is 1/2. In this paper, it is shown that the authors' scheme can be altered slightly so as to obtain an almost perfect teleportation for an appreciable value of |α| 2 . For |α| 2 = 5, the minimum of average fidelity, which is the minimum of the sum of the product of probability of occurrence of any case, and the corresponding fidelity is less than 1 by a quantity ∼10 −4 . We also discuss the effect of decoherence on teleportation fidelity. We find that if no photons are counted in both final outputs, the minimum assured fidelity is still non-zero except when there is no decoherence and the information is an even coherent state. For non-zero photon counts, minimum assured fidelity decreases with an 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 information for low values of |α| 2 only.
This paper investigates the theoretical basis and actual methods for teleporting entangled states using multiple particles. Beginning with Bennett et al.'s pioneering work in 1993, which established the notion of quantum teleportation. In this paper, I will discuss the quantum teleportation, quantum entanglement, Entanglement schemes such as Entanglement swapping scheme and will find out the rate of successful teleportation in terms of fidelity. Additionally discussed is minimal assured fidelity, which is the lowest level of fidelity for any unknown quantum information about the states[1]. Additionally, the success rate of teleporting a superposition of odd and even coherent states is demonstrated to be able to be raised from 50% to almost 99%[2]. We discover that by just isolating the vacuum state from the even state, it can virtually transport, divert, and exchange. Key Words: Entanglement, Quantum teleportation, Entanglement swapping scheme, Bell state measurement (BSM), Quantum information.
In the present paper, we will review the methods to produce superposition of entangled coherent state using polarizing beam splitter and Kerr non linearity. These coherent states have many attractive features and can be used in various schemes. Entanglement, refers to the superposition of a multiparticle system and explains a new type of correlations between any two subsystems of the quantum system, which is not existing in the classical physics. The present paper deals with the use of these states in quantum teleportation, entanglement diversion and entanglement swapping schemes. Entanglement diversion and entanglement-swapping refers to a scheme which may entangle those particles which had never interacted before. In the swapping scheme, two pairs of entangled state are taken. One particle from each pair is subjected to a Bell-state-measurement. This would result in projection of the other two outgoing particles in an entangled pair. Quantum Teleportation of two mode and three modes states is also studied with perfect fidelity. Minimum assured fidelity which is defined as the minimum of the fidelity for any unknown quantum information of the states is also discussed. It is also shown how the success rate of teleportation of a superposition of odd and even coherent states can be increased from 50% to almost 100%. The scheme suggested by van Enk and Hirota was modified by Prakash, Chandra, Prakash and Shivani in 2007. We find that an almost teleportation, diversion and swapping is possible by simply separating vacuum state from the even state. The present paper also deals with study of effect of decoherence and noise on these states and the effect of noise on fidelity and minimum assured fidelity. It is also discussed that these schemes can also be applied to the process of entanglement diversion and entanglement swapping.
We consider the problem of teleporting superposed coherent state using non-maximally entangled coherent state as quantum channel and study the effect of entanglement over quality of teleportation. We show that if maximally entangled coherent state (MECS) used by Van Enk and Hirota [Phys. Rev. A 64, 022313 (2001)] and by H Prakash et al. [Phys. Rev. A 75, 044305 (2007)] is replaced by a particular non-maximally entangled coherent state (NMECS), average fidelity of quantum teleportation increases appreciably at small coherent amplitudes. Since it is very challenging to produce superposed coherent states of large coherent amplitudes, the particular NMECS appear to be a good quantum channel for teleportation at small coherent amplitudes for practical implementation.
Quantum teleportation of qudits is revisited. In particular, we analyze the case where the quantum channel corresponds to a nonmaximally entangled state and show that the success of the protocol is directly related to the problem of distinguishing nonorthogonal quantum states. The teleportation channel can be seen as a coherent superposition of two channels, one of them being a maximally entangled state, thus leading to perfect teleportation, and the other, corresponding to a nonmaximally entangled state living in a subspace of the d-dimensional Hilbert space. The second channel leads to a teleported state with reduced fidelity. We calculate the average fidelity of the process and show its optimality.
We consider the scheme proposed by Wang [Phys. Rev. A64 (2001) 022302] for teleporting bipartite entangled states, which is a superposition of coherent states |α,α〉 and |-α,-α〉, with our suggested modification [Phys. Rev. A75 (2007) 044305] and discuss the effect of decoherence on teleportation fidelity. We find that if no photons are counted in both final outputs, the minimum assured fidelity (MAF), which is the minimum of the fidelity for any arbitrary information), is still nonzero except for the case when there is no decoherence and the information is in even coherent state. For non-zero photon counts, MAF decreases with increase in |α|2 for low noise but in the case of high noise, it increases, attains a maximum value and then decreases with |α|2. We discuss the variation of average fidelity with |α|2 and show that it depends appreciably on the information for low values of |α|2 only.