  We carry out a systematic analysis of a pair of coupled qubits, each of which
is subject to its own dissipative environment, and argue that a combination of
the inter-qubit couplings which provides for the lowest possible decoherence
rates corresponds to the incidence of a double spectral degeneracy in the
two-qubit system. We support this general argument by the results of of an
evolutionary genetic algorithm which can also be used for optimizing
time-dependent processes (gates) and their sequences that implement various
quantum computing protocols.
