Single atom-scale diamond defect allows a large Aharonov-Casher phase

We propose an experiment that would produce and measure a large Aharonov-Casher (AC) 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 nitrogen-vacancy (N-V) defect, replacing interferometer trajectories, are coherently controlled by microwave pulses. The AC 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. ©2009 The American Physical Society