  We propose an experiment that would produce and measure a large
Aharonov-Casher (A-C) phase in a solid-state system under macroscopic motion. A
diamond crystal is mounted on a spinning disk in the presence of a uniform
electric field. Internal magnetic states of a single NV defect, replacing
interferometer trajectories, are coherently controlled by microwave pulses. The
A-C phase shift is manifested as a relative phase, of up to 17 radians, between
components of a superposition of magnetic substates, which is two orders of
magnitude larger than that measured in any other atom-scale quantum system.
