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

(1)包括量子隐形传态在内的量子信道分类研究通常的光通信使用激光作为信号，用相干态在数学上表示。同时指出，利用相干态压缩得到的压缩态可以实现相当有效的通信。在本研究中，(i)构造了将压缩状态传递到保持压缩特性的输出状态的压缩通道的数学模型，即利用对称Fock空间上定义的压缩酉算子构造了一个守恒能量下的压缩通道；（ii）基于(1)的结果，将量子通信信道分为相干信道、压缩信道、光子数信道等。(2)量子逻辑门结构的研究与或门的不可逆性给普通计算机带来了不可避免的缺点。这一缺点的解决方案之一是Fredkin和Foffoli引入的具有三个输入和三个输出的可逆逻辑门，称为傅立叶变换门。Miburn提出了一种由Mach- Zender干涉仪和Kerr器件构成的FTM栅极的物理模型，称为FTM栅极。我们利用量子通道重新构造了该光纤光栅门，并利用量子互熵研究了该光纤光栅的效率。这种光纤光栅门需要光子数态，而控制门在物理上很难实现。在本研究中，我们使用相干控制态来代替光子数态来构建FTM门，并引入了具有四个分束器的新型量子逻辑门。

(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.