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Explanation and Realisation of Quantum Teleportation and its Applications


Quantum Teleportation is a means to transfer the state of a quantum system over large lengths by using entanglement (Zeilinger, 2007). Since ancient times, it is a desire to be able to travel from one place to another instantaneously. The basic idea of teleportation is that the sender examines the object to be teleported and sends the read information to the receiver, which then uses this information to restructure the object (Bouwmeester et al., 2000). However, success can not be achieved in this manner according to quantum mechanics, since both portray the concept in a different way. Determining the quantum state by measurement is impossible if only one object is within reach. Quantum state represents all probabilistic information about an object and thus making use of quantum entanglement, quantum teleportation can be made possible (Zeilinger, 2007). Experimentally, the teleported thing is the information represented by an object and not the substance, of which it is made. Entanglement can be used for teleportation where sender (Alice) is in control of the teleportee photon in a quantum state, not aware of it, and the receiver (Bob) shares an auxiliary pair of entangled photons, as shown in figure1.
The sender has an original particle and both share an auxiliary entangled pair. Performing the Bell measurement, the sender transmits the random outcome to the receiver who, by performing unitary transformation, can change the ancillary photon into a copy of the original (Zeilinger, 2007). Quantum teleportation is considered to be the basic building block of future quantum computer networks and it would permit the transmission of the quantum output to another quantum computer as a quantum input (Zeilinger, 2007). According to Zhang et al., (2000), quantum teleportation implies the transfer of a state over an absolute spatial distance by manipulating the prearranged entanglement of quantum systems in relation to the transmission of minimum information. Later researchers developed protocols for teleportation with three stages; preparation of Einstein-Podolsky-Rosen (EPR) entangled particle source where sender and receiver share the particle from the source, secondly, performing the Bell-operator measurement by sender on his EPR particle and the target particle with unknown quantum state and finally transmitting the result of measurement to the receiver. After this applying the unitary operation on receiver's EPR particle and the unknown state of particle is removed at sender site and its replica appears on receiver's site. The state of teleportation is not found between the two sites during transfer (Zhang et al., 2000). Noh and Carmichael (2006) considered an optical field for teleportation protocol with a finite bandwidth as input. Figure2. illustrates the teleportation protocol based on the concept of sender and receiver (Zeilinger, 2007).

Theoretical and Experimental Realizations

Many attractive theoretical developments were brought in from the time of publication of protocols especially the one presented by Zhang et al., (2000). According to the research conducted by (Noh and Carmichael, 2006), Vaidman (1994) presented the use of non-local measurements for teleportation of unknown quantum states with continuous variables, also provided a method for two way teleportation. Further to this research, Braunstein & Kimble (1998) analysed to integrate finite degree of correlation between relevant particles and also to include inefficiencies in the process of measurement. Zubairy et al., (2003) dealt with the teleportation of a field state from a high Q cavity to another one. Introducing the interspecies teleportation system Maierle et al., (1998) proposed that the information in a superposition of molecular chiral amplitudes needs to be teleported to a photon. Then presenting the QT as an essential ingredient for quantum computing and implementation of it with a simple circuit, Brassard et al., (2004) pursued QT as a primitive operation in quantum computing (Zhang et al., 2000).

Application of quantum mutual entropy to characterize the quantum teleportation process with the help of nonlinear channel involves the basic concept of quantum teleportation channel based on the original teleportation system which was used along with deriving the mutual entropy for the information transmission in the quantum teleportation channel. As a result the information could be transmitted through the linear quantum teleportation channel but generally the associated channel become nonlinear and the information conservation becomes difficult to be studied (Inoue et al., 1998).

Another application involves the abstraction of quantum teleportation and use of local cloning for splitting of entanglement having multiple senders and receivers (Ghiu, 2007). Moving to another application of quantum teleportation Sherson et al., (2006) discussed the quantum teleportation of light and matter. This was performed as a first successful teleportation between objects of different natures. Previous experiments were performed with two different light beams, then it became possible to transfer attributes of a stored photon to another object of same kind and recently scientists have shown the transfer of quantum states of a light pulse to a macroscopic object, which is a group of 1012 atoms. This provides a way for practical application in realization of quantum computers or transmission of coded data i.e., quantum cryptography.

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