  We analyze the posibility of employing the mesoscopic-nanoscopic ring of a
normal metal in a doubly degenerate persistent current state with a third
auxihilary level and in the presence of the Aharonov-Bohm flux equal to the
half of the normal flux quantum $\hbar c/e$ as a qubit. The auxiliary level can
be effectively used for all fundamental quantum logic gate (qu-gate) operations
which includes the initialization, phase rotation, bit flip and the Hadamard
transformation as well as the double-qubit controlled operations (conditional
bit flip). We suggest a tentative realization of the mechanism as either the
mesoscopic structure of three quantum dots coherently coupled by mesoscopic
tunnelling in crossed magnetic and electric fields, or as a nanoscopic
structure of triple anionic vacancy (similar to $F_3$ centers in alkali
halides) with one trapped electron in one spin projection state.
