We show that an array of polar molecules interacting with Rydberg atoms is a
promising hybrid system for scalable quantum computation. Quantum information
is stored in long-lived hyperfine or rotational states of molecules which
interact indirectly through resonant dipole-dipole interactions with Rydberg
atoms. A two-qubit gate based on this interaction has a duration of 1 μs
and an achievable fidelity of 99.9%. The gate is insensitive to the motional
states of the particles -- the molecules can be in thermal states, the atoms do
not need to be trapped during Rydberg excitation, the gate does not heat the
molecules, and heating of the atoms is irrelevant. Within a large, static
array, the gate can be applied to arbitrary pairs of molecules separated by
tens of micrometres, making the scheme highly scalable. The molecule-atom
interaction can also be used for rapid qubit initialization and efficient,
non-destructive qubit readout, without driving any molecular transitions.
Single qubit gates are driven using microwave pulses alone, exploiting the
strong electric dipole transitions between rotational states. Thus, all
operations required for large scale quantum computation can be done without
moving the molecules or exciting them out of their ground electronic states.Comment: 16 pages, 7 figure