  The effect of temperature on the operation of the elementary quantum-dot spin
gates for single-electron computing is studied theoretically within the
framework of the Hubbard model by the example of the NOT-AND gate. The
calculated values of the uniform external magnetic field necessary to realize
the whole truth table proved to be unreasonably high for the implementation of
the NOT-AND logical function even at the liquid helium temperature. This result
appears to be common to all spin gates. Thus, finite temperatures seem to be a
serious obstacle for the practical realization of ground state calculations in
quantum dot spin gates.
