  Hybrid quantum systems have been developed with various mechanical, optical
and microwave harmonic oscillators. The coupling produces a rich library of
interactions including two mode squeezing, swapping interactions, back-action
evasion and thermal control. In a multimode mechanical system, coupling
resonators of different scales (both in frequency and mass) leverages the
advantages of each resonance. For example: a high frequency, easily manipulated
resonator could be entangled with a low frequency massive object for tests of
gravitational decoherence. Here we demonstrate coherent optomechanical state
swapping between two spatially and frequency separated resonators with a mass
ratio of 4. We find that, by using two laser beams far detuned from an optical
cavity resonance, efficient state transfer is possible through a process very
similar to STIRAP (Stimulated Raman Adiabatic Passage) in atomic physics.
Although the demonstration is classical, the same technique can be used to
generate entanglement between oscillators in the quantum regime.
