High coherence fluxonium manufactured with a wafer-scale uniformity process

TL;DR

This paper presents a wafer-scale fabrication process for fluxonium qubits that achieves high uniformity and yield, enabling scalable production of high-coherence quantum processors with millisecond relaxation times.

Contribution

Introduces a novel overlap fabrication process for Josephson junctions that ensures near 100% yield and uniformity across large wafers, facilitating scalable fluxonium qubit production.

Findings

Achieved fluxonium qubits with relaxation times over 1 ms.

Demonstrated uniformity with less than 5% variation in junction parameters.

Enabled scalable fabrication compatible with CMOS processes.

Abstract

Fluxonium qubits are recognized for their high coherence times and high operation fidelities, attributed to their unique design incorporating a superinductor, which is typically implemented using an array of over 100 Josephson junctions. However, this complexity poses significant fabrication challenges, particularly in achieving high yield and junction uniformity with traditional methods. Here, we introduce an overlap process for Josephson junction fabrication that achieves nearly 100% yield and maintains uniformity across a 2-inch wafer with less than 5% variation for the phase slip junction and less than 2% for the entire junction array. We use a compact junction array design that achieves state-of-the-art dielectric loss tangents and flux noise levels, as confirmed by multiple devices. This enables fluxonium qubits to reach energy relaxation times exceeding 1 millisecond at the flux frustration point. This work paves the way for scalable high coherence fluxonium processors using CMOS-compatible processes, marking a significant step towards practical quantum computing.