  Quantum-circuit optimization is essential for any practical realization of
quantum computation, in order to beat decoherence. We present a scheme for
implementing the final stage in the compilation of quantum circuits, i.e., for
finding the actual physical realizations of the individual modules in the
quantum-gate library. We find that numerical optimization can be efficiently
utilized in order to generate the appropriate control-parameter sequences which
produce the desired three-qubit modules within the Josephson charge-qubit
model. Our work suggests ways in which one can in fact considerably reduce the
number of gates required to implement a given quantum circuit, hence
diminishing idle time and significantly accelerating the execution of quantum
algorithms.
