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Nanotube mechanical resonators with quality factors of up to 5 million

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 Added by Joel Moser
 Publication date 2015
  fields Physics
and research's language is English




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Carbon nanotube mechanical resonators have attracted considerable interest because of their small mass, the high quality of their surface, and the pristine electronic states they host. However, their small dimensions result in fragile vibrational states that are difficult to measure. Here we observe quality factors $Q$ as high as $5times10^6$ in ultra-clean nanotube resonators at a cryostat temperature of 30 mK, where we define $Q$ as the ratio of the resonant frequency over the linewidth. Measuring such high quality factors requires both employing an ultra-low noise method to detect minuscule vibrations rapidly, and carefully reducing the noise of the electrostatic environment. We observe that the measured quality factors fluctuate because of fluctuations of the resonant frequency. The quality factors we measure are record high; they are comparable to the highest $Q$ reported in mechanical resonators of much larger size, a remarkable result considering that reducing the size of resonators is usually concomitant with decreasing quality factors. The combination of ultra-low size and very large $Q$ offers new opportunities for ultra-sensitive detection schemes and quantum optomechanical experiments.



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We describe the fabrication and measurement of microwave coplanar waveguide resonators with internal quality factors above 10 million at high microwave powers and over 1 million at low powers, with the best low power results approaching 2 million, corresponding to ~1 photon in the resonator. These quality factors are achieved by controllably producing very smooth and clean interfaces between the resonators aluminum metallization and the underlying single crystal sapphire substrate. Additionally, we describe a method for analyzing the resonator microwave response, with which we can directly determine the internal quality factor and frequency of a resonator embedded in an imperfect measurement circuit.
130 - Y. Tao , J. M. Boss , B. A. Moores 2012
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