Probing Rotational Decoherence with a Trapped-Ion Planar Rotor.

The quantum rotor is one of the simplest model systems in quantum mechanics, but only in recent years has theoretical work revealed general fundamental scaling laws for its decoherence. For example, a superposition of orientations decoheres at a rate proportional to the sine squared of the angle between them. Here, we observe scaling laws for rotational decoherence dynamics for the first time, using a 4  μm diameter planar rotor composed of two Paul-trapped ions.