Tunable Superconductor Insulator Transition in a Quantum Phase Slip Interference Device

The duality between quantum phase slip nanowires and Josephson junctions has triggered a variety of theoretical and experimental works. However, many aspects of these fluctuations are still not fully understood, especially when interference effects are considered.

We present a realization of a quantum phase slip interferometer based on two strongly coupled granular aluminum nanowires connected in series. In the experiment, the interference is controlled by a gate voltage and manifests as a periodic modulation of the critical Coulomb blockade voltage. Our data show that the modulation amplitude depends on the homogeneity of the wires. To improve the wire homogeneity, we employ the intrinsic electromigration technique ([1]) which allows to adjust the resistances and thus the Coulomb blockade of the individual wires. We observe a strong destructive interference of quantum phase slips, displaying a transition from the insulating to a superconducting state. The circuit is analyzed in detail and future applications are proposed.

[1] J. N. Voss, Y. Schön, M. Wildermuth, D. Dorer, J. H. Cole, H. Rotzinger and A. V. Ustinov, ACS Nano 15 (2021)