Fluxonium: single Cooper pair circuit free of charge offsets

TL;DR

This paper introduces Fluxonium, a superconducting circuit that is immune to offset charges, enhancing stability for quantum computing and metrology applications by using a novel junction configuration.

Contribution

The paper presents a new superconducting circuit design that eliminates offset charge sensitivity, improving coherence and stability for quantum technologies.

Findings

Fluxonium is insensitive to offset charges due to its unique junction configuration.

The energy levels of Fluxonium exhibit anharmonicity suitable for quantum computation.

Experimental realization demonstrates improved charge stability.

Abstract

The promise of single Cooper pair quantum circuits based on tunnel junctions for metrology and quantum information applications is severely limited by the influence of "offset" charges - random, slowly drifting microscopic charges inherent to many solid-state systems. By shunting a small junction with the Josephson kinetic inductance of a series array of large capacitance tunnel junctions, thereby ensuring that all superconducting islands are connected to the circuit by at least one large junction, we have realized a new superconducting artificial atom which is totally insensitive to offset charges. Yet, its energy levels manifest the anharmonic structure associated with single Cooper pair effects, a useful component for solid state quantum computation.