Recent experimental result has revealed that the Bohr’s quantization violates symmetry between opposite directions on the macroscopic level. This breach of symmetry is connected with challenge to the law of momentum conservation and the second law of thermodynamics.
After the brief discussion of the internal degrees of freedom of atomic systems, we give an overview of how these variables can acquire nonvanishing average values in an ensemble of atoms. Optical pumping was one of the first experimental schemes that allowed physical systems to be pushed far from equilibrium through the interaction with light, a direct consequence of angular momentum conservation and the symmetry properties of the interaction between atoms and radiation. Principle and overview Phenomenology Optical pumping (Happer 1972) is one of the earliest examples wherein optical radiation qualitatively modifies the properties of a material system. In its original implementation, it corresponds to a selective population of specific angular momentum states, starting from thermal equilibrium. In the idealised process depicted in Figure 5.1, the light brings the atomic system from the initially disordered state, in which the populations of degenerate levels are equal, into an ordered state where the internal state of all atoms is the same. If we consider only the material system, it appears as if the evolution from the initially disordered state into an ordered state, where the population of one level is higher than that of another level, violated the second law of thermodynamics. This process does not proceed spontaneously, however. It is the interaction with polarised light that drives the system and increased disorder in the radiation field compensates for the increase in the population difference in the material system (Enk and Nienhuis 1992).
In order to have a chance to make a real quantum computer it is important to find the entanglement phenomenon on mesoscopic level since technology can not be able in the visible future to work on atomic level. It is known that the entanglement (the EPR correlation) violates the principle of local realism. Existence of EPR correlation on a level higher than atomic one violates both local and macroscopic realism. In order to clear possibility of this violation the fundamental difference between applications of the principles of quantum mechanics on atomic and higher level is considered. Mysterious nature of some macroscopic quantum phenomena is accentuated. Experimental verification of the entanglement possibility in superconductor structure is proposed.