  Topological operations have the merit of achieving certain goals without
requiring accurate control over local operational details. To date, topological
operations have been used to control geometric phases, and have been proposed
as a means for controlling the state of certain systems within their degenerate
subspaces[1-8]. More recently, it was predicted that topological operations can
be extended to transfer energy between normal modes, provided that the system
possesses a specific type of degeneracy known as an exceptional point
(EP)[9-11]. Here we demonstrate the transfer of energy between two modes of a
cryogenic optomechanical device by topological operations. We show that this
transfer arises from the presence of an EP in the device's spectrum. We also
show that this transfer is non-reciprocal[12-14]. These results open new
directions in system control; they also open the possibility of exploring other
dynamical effects related to EPs[15,16], as well as the behavior of thermal and
quantum fluctuations in the vicinity of EPs.
