On-Demand Correlated Errors in Superconducting Qubits from a Particle Accelerator

TL;DR

This paper introduces a novel experimental setup coupling a particle accelerator with a dilution refrigerator to study ionizing radiation effects on superconducting qubits, revealing error mechanisms and dependencies crucial for quantum error correction.

Contribution

It presents a new facility that enables controlled, on-demand ionizing radiation exposure to superconducting qubits, allowing detailed study of radiation-induced errors and their dependence on device parameters.

Findings

Radiation causes relaxation, excitation, and detuning errors in qubits.

Error signatures depend on junction placement and superconducting gaps.

The setup mimics cosmic-ray muon energy deposition.

Abstract

Ionizing radiation is a known source of correlated errors in superconducting quantum processors, inhibiting the functionality of quantum error correction surface codes. High-energy photons and charged particles deposit pair-breaking energy into these systems leading to excess quasiparticles near Josephson junctions that increase qubit decoherence. Previous investigations of this problem have relied on ambient, stochastic sources of ionizing radiation or alternative methods of quasiparticle generation. Here, we present a facility that couples an electron linear accelerator (linac) to a dilution refrigerator to study ionizing radiation in quantum systems. A single linac electron closely mimics the energy deposition characteristics of a typical cosmic-ray muon, and we demonstrate the facility's usefulness with a multi-qubit superconducting transmon chip. Characteristic radiation-induced relaxation errors are quickly and easily collected with the speed and timing information of the linac. Additionally, we present qubit excitation and detuning errors that can be difficult to detect without the on-demand source of ionizing radiation. These error signatures are shown to be dependent on the junction placement and surrounding superconducting gaps.