  We consider stimulated Raman adiabatic passage (STIRAP) processes in tripod
systems and show how to generate purely geometric phase changes of the quantum
states involved. The geometric phases are controlled by three laser fields
where pulse shapes, relative field strength and phases can be controlled. We
present a robust set of universal gates for quantum computing based on these
geometric phases: a one-qubit phase gate, a Hadamard gate and a two-qubit phase
gate.
