Two-level system as topological actuator for nanomechanical modes

This work shows how a nano-mechanical oscillator coupled to an open quantum two-level system can exhibit exceptional degeneracy points in its spectrum. By encircling the exceptional point in parameter space, the papers shows the rotation of the polarization of the mechanical modes in real space, which enables a topological and chiral actuation between the modes, even in the presence of strong quantum fluctuations due to the spontaneous emission of the two-level system.