All-nitride superconducting qubits based on atomic layer deposition

TL;DR

This paper demonstrates the fabrication of superconducting qubits using atomic layer deposition of NbN/AlN/NbN trilayers, achieving high coherence times at elevated temperatures, and establishing ALD as a scalable technique for quantum circuits.

Contribution

It introduces all-nitride superconducting qubits fabricated via ALD, showing their potential for high-temperature operation and scalable quantum device manufacturing.

Findings

Josephson tunneling with varied barrier thicknesses

Microsecond-scale relaxation times above 300 mK

ALD as a viable low-temperature deposition method

Abstract

The development of large-scale quantum processors benefits from superconducting qubits that can operate at elevated temperatures and be fabricated with scalable, foundry-compatible processes. Atomic layer deposition (ALD) is increasingly being adopted as an industrial standard for thin-film growth, particularly in applications requiring precise control over layer thickness and composition. Here, we report superconducting qubits based on NbN/AlN/NbN trilayers deposited entirely by ALD. By varying the number of ALD cycles used to form the AlN barrier, we achieve Josephson tunneling through barriers of different thicknesses, with critical current density spanning seven orders of magnitude, demonstrating the uniformity and versatility of the process. Owing to the high critical temperature of NbN, transmon qubits based on these all-nitride trilayers exhibit microsecond-scale relaxation times, even at temperatures above 300 mK. These results establish ALD as a viable low-temperature deposition technique for superconducting quantum circuits and position all-nitride ALD qubits as a promising platform for operation at elevated temperatures.