  The confidence of many authors in the possibility to use superconducting loop
interrupted by Josephson junctions as a basis for quantum bit, flux qubit,
presumes the assumption on superposition of two macroscopically distinct
quantum states with macroscopically different angular momentum. The
contradiction of this assumption with macroscopic realism and the conservation
law must call the numerous publications about flux qubit in question. These
publications uncover misunderstanding by many modern physicists of the essence
of the superposition principle. The Einstein - Podolsky - Rosen (EPR)
correlation or entanglement, introduced in 1935 by opponents of the Copenhagen
interpretation in order to reveal the contradiction of this principle with
realism, has provided a basis of the idea of quantum computation. The problem
of the EPR correlation has emerged thanks to philosophical controversy between
the creators of the quantum theory about the subject of its description.
Therefore it is impossible to solve correctly the problem of quantum computer
creation without the insight into the essence of this philosophical
controversy. The total neglect of the philosophical problems of quantum
foundation results to concrete mistakes, the example of which are the
publications about flux qubit. In order to prevent such mistakes in the future
the philosophical questions about the essence of superposition and entanglement
and about the subject of quantum description are considered.
