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Ultracoherent Nanomechanical Oscillators for Quantum Optomechanics: Joint CIQC / Nano Seminar

September 16 @ 2:00 pm - 3:00 pm

Prof. Tobias J. Kippenberg, EPFL Lausanne / Physics & EE
The reduction of mechanical dissipation increases force sensitivity of mechanical oscillators and decreases the thermal decoherence rate of mechanical quantum states. Concomitantly, reduced size allows stronger coupling to other degrees of freedom such as electromagnetic fields. These two demands are conflicting: due to surface losses, smaller size typically leads to increased dissipation. However, the phenomenon ‘dissipation dilution’, where mechanical losses are diluted by stress, breaks the trend.
Over the last decade, dissipation dilution has been exploited to reduce the dissipation of nanomechanical resonators by three orders of magnitude; thereby allowing nanomechanical oscillators to surpass the quality factors of the best macroscopic oscillators. In this seminar, I will show three resonator classes where dissipation dilution is greatly enhanced by engineering the resonator geometry. Our best devices show mechanical quality factors exceeding 3 billion at room temperature, giving decoherence rates approaching those of optically levitated nanoparticles.
Finally, I will present a new material platform for nanomechanics: single-crystal strained silicon—a material developed for implementing high mobility transistors. The strained silicon nanostrings support MHz mechanical modes with Q exceeding 109 at room temperature and 1010 at 6 K, surpassing state-of-the-art implementations in Si3N4. These mechanical resonators are ideal force detectors with thermal-limited force sensitivities beyond those of the best AFM cantilevers and invite application in quantum optomechanical systems.
Tobias Kippenberg did his PhD at Caltech in Applied Physics and postdocs at LMU and MPI-Quantum before joining EPFL. Several early career awards included the EU Young Scientist contest and the Helmholtz Prize. He rose to full professor in 2013 and recently won the RW Wood Prize (2021).


September 16
2:00 pm - 3:00 pm


180 Tan Hall