Optomech · Quantum opto-mechanics with photonic and phononic crystals

Quantum opto-mechanics with photonic and phononic crystals

During the 36 months of the project OPTOMECH the underlying goal was to demonstrate quantum experiments with optomechanical systems. While the initial period was more focused on developing techniques, devices and experiments, the second part's focus shifted towards the actual experiments with such meso- and macorscopic mechanical devices. One of the main goals was to realize ground-state cooling of an optomechanical device, which has been achieved, initially in a continuous flow 4He cryostat and using the radiation-pressure interaction in order to side-band cooling into the ground-state [1]. Purely passive cooling of the resonator into its ground-state with the help of a dilution refrigerator has taken longer to realize as it proved very difficult due to surface absorption effects in the silicon device. An improved coupling scheme and several other technical and conceptual improvements have allowed for a recent demonstration of ground-state cooling in a dilution refrigerator [2]. Both experiments were firsts in optomechanical systems and will pave the way for numerous quantum experiments involving such mechanical oscillators. Very recently, we have demonstrated a novel method to detect and understand the phonon statistic of the mechanical oscillator, by mapping it onto the light field through the radiation pressure force and detect it using superconducting single photon detectors [3]. This opens up the possibility of generating non-classical mechanical states [4], as envisioned in the proposal. This exciting goal is within imminent reach and experiments are currently under way that should allow us to demonstrate these quantum effects of mechanical oscillators. We have also demonstrated that, with the help of a highly efficient coupling scheme [5], we were able to alter the statistics of the optical field and perform novel quantum experiments with our optomechanical systems. The continuous measurement of the mechanical oscillators position inside the optomechanical cavity can lead to squeezing of the noise fluctuations of the optical probe field below that of shot-noise, i.e. the vacuum noise of the light itself. We have achieved such squeezing [6], which is normally only observed in non-linear media, in one of our structures. Despite being a slightly different quantum experiment than originally envisioned in the proposal, this experiment constitutes a major milestone in optomechanics. [1] J. Chan, T. P. Mayer Alegre, A. H. Safavi-Naeini, J. T. Hill, A. Krause, S. Gröblacher, M. Aspelmeyer, and O. Painter, Laser cooling of a nanomechanical oscillator into its quantum ground state, Nature 478, 89 – 92 (2011). [2] S. M. Meenehan*, J. D. Cohen*, S. Gröblacher*, J. T. Hill, A. H. Safavi-Naeini, M. Aspelmeyer, and O. Painter, Silicon optomechanical crystal resonator at millikelvin temperatures, Phys. Rev. A 90, 011803(R) (2014). [3] J. D. Cohen*, S. M. Meenehan*, G. S. MacCabe, S Gröblacher, A. H. Safavi-Naeini, F. Marsili, M. D. Shaw, and O. Painter, Phonon counting and intensity interferometry of a nanomechanical resonator, arXiv:1410.1047 (2014). [4] M. R. Vanner, M. Aspelmeyer, and M. S. Kim, Quantum State Orthogonalization and a Toolset for Quantum Optomechanical Phonon Control, Phys. Rev. Lett. 110, 010504 (2013). 5] S. Gröblacher*, J. T. Hill*, A. H. Safavi-Naeini*, J. Chan, and O. Painter, Highly efficient coupling from an optical fiber to a nanoscale silicon optomechanical cavity, Appl. Phys. Lett. 103, 181104 (2013). [6] A. H. Safavi-Naeini*, S. Gröblacher*, J. T. Hill*, J. Chan, M. Aspelmeyer, and O. Painter, Squeezed light from a silicon micromechanical resonator, Nature 500, 185 (2013).

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