Speaker
Description
Carbon nanotube (CNT) nanoelectromechanical systems are very sensitive to adsorbed mass and external forces, but accurate readout of CNT vibrational motion is essential for these applications. Conveniently, at cryogenic temperatures a suspended CNT single-electron transistor can self-detect its motion, since the conductance depends on the nanotube’s displacement. However, the ultimate sensitivity depends on how well this small change in conductance can be amplified and read out.
I will show a readout scheme for a CNT mechanical sensor with a Josephson travelling-wave parametric amplifier (TWPA) as primary gain stage. The TWPA is a near-quantum-limited amplifier mounted inside our dilution refrigerator; we have therefore combined technologies for extremely sensitive force detection and state of the art electronic amplification. To make this work, we operate the CNT as a mixer, with frequencies chosen so that the mechanical motion generates sidebands within the 4-7.5 GHz bandwidth of the TWPA.
With this setup, we have achieved fast and sensitive detection of CNT motion. When the vibrating nanotube is operated in the conventional way, as a mechanical resonator, it is a phase-preserving force detector, and we characterize its force sensitivity. We then operate the device as a self-driving mechanical oscillator, and demonstrate phase-sensitive force detection. These results may be promising for future force microscopes based on nanomechanical resonators and harnessing quantum electronics.