Various mesoscopic systems have their own unique characteristics, some of which are of importance due to bridging function over classical and quantum mechanics. It is quite natural that human beings living in macroscopic world could hardly grasp the phenomena occurring in the microscopic world in an intuitive manner. This situation offers a vital sense in the "observation" problem necessarily accompanied with the classical means. The fundamental core of the argument between Einstein-Podolsky-Rosen and Bohr starting in 1935 actually lies in this point. However, recent development of experimental techniques finally comes to suggest the possibility to realise the "Schrodinger-cat states" in a mesoscopic system [I ,2]
