STUDIES ON CLASSIFICATION OF QUANTUM CHANNEL INCLUDING QUANTUM TELEPORTATION AND FORMULATION OF QUANTUM LOGIC GATES

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(1)Study of classification of a quantum channel including quantum teleportationUsual optical communication uses laser as a signal, which is represented by coherent state mathematically. By the way, it is remarked that quite effective communication will be realized by using the squeezed states obtained by squeezing the coherent states. In this study, (i)we construct the mathematical model of squeezing channel which transmits the squeezed states to the output states keeping squeezing property, that is, we construct a squeezing channel under the energy conservation using a squeezing unitary operator defined on symmetric Fock space ; (ii)based on the results of (1), we classified the quantum communication channels such as the coherent channel, the squeezing channel, the photon number channel and so on.(2)Study of construction of quantum logic gateThe irreversibility of the AND and OR gates gives an unavoided demerit in usual computer. One of the solutions of this demerit is a reversible logic gate with three inputs and three outputs introduced by Fredkin and Foffoli, which is called a FT gate. Miburn proposed a physical model of FT gate constructed by a Mach- Zender interferometer and a Kerr device, which is called a FTM gate. We reformulated this FTM gate by using the quantum channel and studied the efficiency of this FTM by means of the quantum mutual entropy. This FTM gate needs the photon number state which might be difficult to realize physicaly for the control gate. In this study, we construct FTM gate using coherent control states instead of the photon number state and we also introduced the new quantum logic gate with four beam splitters.