Observation of strong coupling between a micromechanical resonator and an optical cavity field

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Achieving coherent quantum control over massive mechanical resonators is a current research goal. Nano- and micromechanical devices can be coupled to a variety of systems, for example to single electrons by electrostatic1,2 or magnetic coupling3,4, and to photons by radiation pressure5,6,7,8,9 or optical dipole forces10,11. So far, all such experiments have operated in a regime of weak coupling, in which reversible energy exchange between the mechanical device and its coupled partner is suppressed by fast decoherence of the individual systems to their local environments. Controlled quantum experiments are in principle not possible in such a regime, but instead require strong coupling. So far, this has been demonstrated only between microscopic quantum systems, such as atoms and photons (in the context of cavity quantum electrodynamics12) or solid state qubits and photons13,14. Strong coupling is an essential requirement for the preparation of mechanical quantum states, such as squeezed or entangled states15,16,17,18, and also for using mechanical resonators in the context of quantum information processing, for example, as quantum transducers. Here we report the observation of optomechanical normal mode splitting19,20, which provides unambiguous evidence for strong coupling of cavity photons to a mechanical resonator. This paves the way towards full quantum optical control of nano- and micromechanical devices.

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Figure 1: Experimental set-up and characterization of the uncoupled mechanical and optical oscillator.
Figure 2: Optomechanical normal mode splitting and avoided crossing in the normal-mode frequency spectrum.


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We are grateful to T. Corbitt, C. Genes, S. Goßler, P. K. Lam, G. Milburn, P. Rabl and P. Zoller for discussions. We also thank M. Metzler, R. Ilic and M. Skvarla (CNF), and K. C. Schwab and J. Hertzberg, for microfabrication support, and R. Blach for technical support. We acknowledge financial support from the Austrian Science Fund FWF, the European Commission and the Foundational Questions Institute. S.G. is a recipient of a DOC fellowship of the Austrian Academy of Sciences; S.G. and M.R.V. are members of the FWF doctoral programme Complex Quantum Systems (CoQuS).

Author Contributions All authors have made a significant contribution to the concept, design, execution or interpretation of the presented work.

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Correspondence to Markus Aspelmeyer.

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Gröblacher, S., Hammerer, K., Vanner, M. et al. Observation of strong coupling between a micromechanical resonator and an optical cavity field. Nature 460, 724–727 (2009) doi:10.1038/nature08171

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