Concentric transmon qubit featuring fast tunability and an anisotropic magnetic dipole moment

TL;DR

This paper introduces a novel concentric transmon qubit design with fast tunability and enhanced magnetic dipole moment, demonstrating promising coherence times and potential for site-selective qubit coupling in quantum simulation.

Contribution

The paper presents a new concentric transmon qubit architecture with a gradiometric SQUID loop enabling rapid frequency tuning and increased magnetic dipole moment, advancing quantum circuit control.

Findings

Qubit lifetimes and coherence times around 10 microseconds.

Systematic characterization of loss channels.

Enhanced magnetic dipole moment compared to conventional designs.

Abstract

We present a planar qubit design based on a superconducting circuit that we call concentric transmon. While employing a straightforward fabrication process using Al evaporation and lift-off lithography, we observe qubit lifetimes and coherence times in the order of 10us. We systematically characterize loss channels such as incoherent dielectric loss, Purcell decay and radiative losses. The implementation of a gradiometric SQUID loop allows for a fast tuning of the qubit transition frequency and therefore for full tomographic control of the quantum circuit. Due to the large loop size, the presented qubit architecture features a strongly increased magnetic dipole moment as compared to conventional transmon designs. This renders the concentric transmon a promising candidate to establish a site-selective passive direct Z coupling between neighboring qubits, being a pending quest in the field of quantum simulation.