Persistent, controllable circulation of a polariton ring condensate

Persistent circulation is a canonical effect of superfluidity. In previous experiments, quantized circulation has been observed in polariton condensates, usually far from equilibrium, but persistent circulation without stirring has not. We report here the direct observation of quantized circulation of a polariton condensate in a well-controlled steady state. We can cause the condensate to circulate in either direction on demand using a short laser pulse; after this short pulse, the condensate continues to circulate for dozens to hundreds of rotations around the ring without any further stimulation. Our theoretical model successfully shows how the pulse causes the circulation.