  We describe an electrodynamic mechanism for coherent, quantum mechanical
coupling between spacially separated quantum dots on a microchip. The technique
is based on capacitive interactions between the electron charge and a
superconducting transmission line resonator, and is closely related to atomic
cavity quantum electrodynamics. We investigate several potential applications
of this technique which have varying degrees of complexity. In particular, we
demonstrate that this mechanism allows design and investigation of an on-chip
double-dot microscopic maser. Moreover, the interaction may be extended to
couple spatially separated electron spin states while only virtually populating
fast-decaying superpositions of charge states. This represents an effective,
controllable long-range interaction, which may facilitate implementation of
quantum information processing with electron spin qubits and potentially allow
coupling to other quantum systems such as atomic or superconducting qubits.
