Rabi Oscillations in a Superconducting Nanowire Circuit

At feature sizes of nanometer scale, superconducting wires made from a material with high normal state resistance show a pronounced nonlinear microwave response.
Disordered oxidized (granular) aluminum is a new material for superconducting quantum circuits, featuring not only a very high kinetic inductance but also microwave resonators with high quality factors [1,2]. Microscopically, it can be described as a disordered network of nano-scale aluminum grains, coupled via the Josephson effect [3].
We investigate the circuit quantum electrodynamics of 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 granular aluminum material, we observe lifetimes in the microsecond range. [4]

[1] H. Rotzinger, et al., Supercond. Sci. Technol. 30, 025002 (2016).
[2] L. Grünhaupt, et al., Nat. Mater. 18, 816 (2019).
[3] N. Maleeva, et al., Nat. Commun. 9, 3889 (2018).
[4] Y. Schön, et al., (2019), arXiv:1907.04107 [cond-mat.supr-con].