  We present Monte Carlo wavefunction simulations for quantum computations
employing an exchange-coupled array of quantum dots. Employing a combination of
experimentally and theoretically available parameters, we find that gate
fidelities greater than 98 % may be obtained with current experimental and
technological capabilities. Application to an encoded 3 qubit (nine physical
qubits) Deutsch-Josza computation indicates that the algorithmic fidelity is
more a question of the total time to implement the gates than of the physical
complexity of those gates.
