# Realization of a Carbon-Nanotube-Based Superconducting Qubit

## TL;DR

This paper demonstrates a hybrid superconducting qubit utilizing a carbon nanotube Josephson junction, with voltage tunability and strong coupling to a microwave resonator, advancing solid-state quantum computing components.

## Contribution

It introduces a novel hybrid superconducting qubit with a carbon nanotube junction and demonstrates its tunability and strong coupling in a circuit QED setup.

## Key findings

- Achieved voltage tunability of qubit frequency.
- Observed strong dispersive coupling to a microwave resonator.
- Measured qubit relaxation and coherence times of 10-200 ns.

## Abstract

Hybrid circuit quantum electrodynamics (QED) involves the study of coherent quantum physics in solid state systems via their interactions with superconducting microwave circuits. Here we present an implementation of a hybrid superconducting qubit that employs a carbon nanotube as a Josephson junction. We realize the junction by contacting a carbon nanotube with a superconducting Pd/Al bi-layer, and implement voltage tunability of the qubit frequency using a local electrostatic gate. We demonstrate strong dispersive coupling to a coplanar waveguide resonator via observation of a resonator frequency shift dependent on applied gate voltage. We extract qubit parameters from spectroscopy using dispersive readout and find qubit relaxation and coherence times in the range of $10-200~\rm{ns}$.