Cavity QED offers many tantalising possibilities for interactions between light and matter that may be useful for quantum information processing. In experiments such as those with micromasers, microwave cavities with quality factors in excess of 10^10 have been demonstrated. In these experiments, single Rydberg atoms pass through the cavity and interact with the field. Historically micromasers were built to validate the Jaynes-Cummings model of a two level atom interacting with a single mode field. Modes of a microwave cavity field are an attractive resource for quantum information due to the very high quality of micromaser cavities allowing protection from the environment. Encoding qubits in modes of the field is an obvious step, however it is difficult to conceive of a system that allows a useful interaction between photons whilst keeping the atomic state separable. This is necessary as an atom leaving the cavity after interaction may leak information to the environment.
In this presentation I give a brief description of a micromaser, and show that extensions to the Jaynes-Cummings model can be used to produce effective Hamiltonians that leave the atom separable whilst allowing a universal set of logic gates. These logic gates act on dual-rail qubits, each encoded as a single photon shared in a pair of modes of the field. In such a system, the atoms passing through may be viewed as a clock pulse.