  We consider theoretically the interplay between Zeeman coupling and
exchange-induced swap action in spin-based quantum dot quantum computer models
in the presence of inhomogeneous magnetic fields, which are invariably present
in real systems. We estimate quantitatively swap errors caused by the
inhomogeneous field, establishing that error correction would, in principle, be
possible in the presence of non-uniform magnetic fields in realistic
structures.

Mesoscale and Nanoscale Physics;Quantum Physics