Demonstration of a capacitively shunted superconducting granular aluminum nanowire qubit

At feature sizes of nanometer scale, superconducting wires made from a material with a high normal conducting sheet resistance show a pronounced nonlinear microwave response. If such a nanowire is embedded in a self-resonating... [ view full abstract ]

At feature sizes of nanometer scale, superconducting wires made from a material with a high normal conducting sheet resistance show a pronounced nonlinear microwave response. If such a nanowire is embedded in a self-resonating circuit, the nonlinearity can be observed even at very low photon numbers. Unfortunately, these materials often show a rather high photon loss, which makes them unusable for long lived quantum circuits. Granular aluminum is a new material for superconducting quantum circuits which features not only a very high kinetic inductance but also high quality factors. [1]

We demonstrate a new type of superconducting qubit, exploring the potential of nanowires fabricated from granular aluminum. Replacing the Josephson tunnel junction in a transmon qubit, the granular aluminum nanowire is operated in a high-impedance Josephson weak-link regime.

[1] H. Rotzinger, et al., Supercond. Sci. Technol. 30, 025002 (2016)