Rabi oscillations in a superconducting nanowire circuit

Yannick Schön,Sebastian T Skacel,Jan Nicolas Voss,Jared H Cole,Martin P Weides,Hannes Rotzinger,Micha Wildermuth,Alexey V Ustinov,Andre Schneider

doi:10.1038/s41535-020-0220-x

Abstract

We investigate the circuit quantum electrodynamics of anharmonic superconducting nanowire oscillators. The sample circuit consists of a capacitively shunted nanowire with a width of about 20 nm and a varying length up to 350 nm, capacitively coupled to an on-chip resonator. By applying microwave pulses we observe Rabi oscillations, measure coherence times and the anharmonicity of the circuit. Despite the very compact design, simple top-down fabrication and high degree of disorder in the oxidized (granular) aluminum material used, we observe lifetimes in the microsecond range.

Highlights

Quantum electrodynamics experiments with superconducting circuits usually feature one or more Josephson tunnel junctions embedded in a circuit
We report on a quantum circuit which employs a superconducting nanowire as a nonlinear element
The first option aims at minimizing the amount of high kinetic inductance material, for instance, by using a conventional low kinetic inductance superconductor like aluminum for the capacitive parts. This approach has the advantage that the geometric requirements for the nanowire are less stringent[20,21]

Summary

INTRODUCTION

Quantum electrodynamics experiments with superconducting circuits (cQED) usually feature one or more Josephson tunnel junctions embedded in a circuit. Using the powerful cQED approach, material properties arising at the nanometer scale are studied by directly observing measures like inductance, nonlinearity, or coherence We demonstrate that such a simple circuit has a rather long (~μs) excited state lifetime. The nanowires considered in this paper instead have a lower normal state resistance and, due to the short coherence length (ξ = (8 ± 0.4) nm ≃ w17), the superconducting phase is well defined in the wire This means that Cooper pairs can tunnel coherently along the wire up to its critical current Ic. Ignoring the local structure of the wire, this behavior is rather well described by a mean field approach of the Kulik–Omelyanchuk (KO) model[17,18], which relates Ic to the wire’s superconducting gap and normal state resistance. This would give access to intrinsic dynamics and their contributions to the anharmonicity in disordered one-dimensional systems

RESULTS AND DISCUSSION

CONCLUSION

METHODS

CODE AVAILABILITY