Clean carbon nanotubes coupled to superconducting impedance-matching circuits.

V Ranjan,M Muoth,C Schönenberger,M Jung,T Hasler,G Puebla-Hellmann,C Hierold,A Wallraff,A Nunnenkamp

doi:10.1038/ncomms8165

Abstract

Coupling carbon nanotube devices to microwave circuits offers a significant increase in bandwidth (BW) and signal-to-noise ratio. These facilitate fast non-invasive readouts important for quantum information processing, shot noise and correlation measurements. However, creation of a device that unites a low-disorder nanotube with a low-loss microwave resonator has so far remained a challenge, due to fabrication incompatibility of one with the other. Employing a mechanical transfer method, we successfully couple a nanotube to a gigahertz superconducting matching circuit and thereby retain pristine transport characteristics such as the control over formation of, and coupling strengths between, the quantum dots. Resonance response to changes in conductance and susceptance further enables quantitative parameter extraction. The achieved near matching is a step forward promising high-BW noise correlation measurements on high impedance devices such as quantum dot circuits.

Highlights

Coupling carbon nanotube devices to microwave circuits offers a significant increase in bandwidth (BW) and signal-to-noise ratio
A key advance in this hybrid-carbon nanotubes (CNT) device is the implementation of a mechanical transfer at ambient conditions
We have operated a radio frequency (RF) superconducting impedancematching circuit to measure CNT quantum dots in a hybrid device fabricated using a mechanical transfer of CNTs

Summary

Introduction

Coupling carbon nanotube devices to microwave circuits offers a significant increase in bandwidth (BW) and signal-to-noise ratio. The circuit offers bandwidths (BW) in the MHz range even for device impedances on the order of 1 MO These features, on one hand, allow us to perform high-BW measurements for deducing both conductance and susceptance changes in the quantum device at GHz frequencies, and on another hand, provide near unity collection of emitted radiation power for fast shot noise measurements. Through a mechanical transfer process[27], we place the CNT on the finished microwave device in the last step Such a selective assembly technique[13] allows us to address the mentioned fabrication and yield issues while obtaining clean transport spectra in combination with low microwave loss circuits. By performing simultaneous measurements of resistance and complex impedance, we observe good quantitative agreement between direct current (DC) conductance and RF measurements

Methods

Results

Conclusion