Circuit quantum electrodynamics with carbon-nanotube-based superconducting quantum circuits

Dr Matthias Mergenthaler, Professor Andrew Briggs and colleagues from Oxford Physics, the University of Basel and the University of Lancaster worked on developing a hybrid superconducting qubit using a carbon nanotube as a Josephson junction.

The junction was realised by contacting a carbon nanotube with a superconducting Pd/Al bilayer, and implementing voltage tunability of the quantum circuit's frequency using using a local electrostatic gate.

In their paper 'Circuit Quantum Electrodynamics with Carbone-Nanotube-Based Superconducting Quantum Circuits' published in Physical Review Applied, the team demonstrate a strong dispersive coupling to a coplanar waveguide resonator by investigating the gate-tunable resonator frequency.  The qubit parameteres were extracted from spectroscopy using dispersive readout, and the team found the qubit relaxation and coherence times were in the 10-200 ns range.