  We investigate a hybrid quantum circuit where ensembles of cold polar
molecules serve as long-lived quantum memories and optical interfaces for solid
state quantum processors. The quantum memory realized by collective spin states
(ensemble qubit) is coupled to a high-Q stripline cavity via microwave Raman
processes. We show that for convenient trap-surface distances of a few $\mu$m,
strong coupling between the cavity and ensemble qubit can be achieved. We
discuss basic quantum information protocols, including a swap from the cavity
photon bus to the molecular quantum memory, and a deterministic two qubit gate.
Finally, we investigate coherence properties of molecular ensemble quantum
bits.
