0 1 2 3 4 5 6 7 8 9 10 0 0.5 1 1.5 n=100 0 n=0 t n  a FIG. 6: The mean photon number in the opto-mechanical cavity versus time showing the effect of the thermal driving of the nanomechanical resonator for ¯ n = 1000, γ = 0 . 9 , κ = 1 . 0 , µ = 0 . 001 and g = 1 . 5. The case of ¯ n = 0 is shown for comparison in the dashed line. We have proposed a novel scheme that allows the coherent exchange of single-photon ex- citations of an optical cavity with a micromechanical resonator. The single-photon coupling is enhanced by a strong pump field that mediates the state transfer, in close analogy to op- tical three-wave mixing. A clear signature of the state transfer between light and mechanics is the oscillation of the added-photon emission probability from the cavity. The scheme can be realized with state-of-the-art optomechanical systems that operate sufficiently close to the quantum ground state. This provides the basis for storage and interacting of optical photons in/via mechanical structures. Note that a similar idea has recently been suggested to create mechanical superposition states [26]. We thank M. Lukin for discussions. GJM wishes to acknowledge the support of the University of Vienna and the Australian Research Council. UA acknowledges the support of the Australian Research Council and the University of Queensland. MA acknowledges support from the Austrian Science Fund (projects P19539, START), the European Commis- sion (project MINOS), the European Research Council (ERC QOM) and the Foundational Acknowledgments 12