  A novel approach is proposed for realizing an arbitrary-operation gate with a
SQUID qubit via pulsed-microwave manipulation. In this approach, the two
logical states of the qubit are represented by the two lowest levels of the
SQUID and an intermediate level is utilized for the gate manipulation. The
method does not involve population in the intermediate level or tunneling
between the two logical qubit states during the gate operation. Morever, we
show that the gate can be much faster than the conventional two-level gate. In
addition, to take the advantage of geometric quantum computing, we further show
how the method can be extended to implement an arbitrary quantum logic
operation in a SQUID qubit via geometric manipulation.
