Abstract
The lineup of the subjects of physics at Juntendo University are first introduced and particle and wave motions in classical theory is reviewed by using video clips of teaching materials. Then, the necessity of quantum theory for the subatomic physics are discussed in terms of the equipartition theorem, blackbody radiation, atomic spectra, and stability of atom. The two characteristic features of quantum theory are the particle-wave duality due to the superposition principle and EPR phenomena in entangled states of composite systems. Owing to recent progress in experimental techniques, the superposition principle of quantum theory is exemplified by a beautiful interference experiment of electron, and the violation of Bell's inequality in an entangled state is verified in favor of quantum theory. The new development in quantum theory, the environmental decoherence theory and logical framework of consistent history, provided a unified description of the classical as well as quantum physics, and motivated the research of technology based on fundamental principle of quantum theory. As a new development of the quantum theory, quantum computer and quantum key distribution to guarantee secure communication, which may as well be considered direct verification of quantum principles, are briefly explained.
