Creating Correlated Errors on Transmon Qubits Using an Electron Linear Accelerator

Superconducting transmon qubits are known to be susceptible to errors due to ionizing radiation from ambient radioactive decay and cosmic ray sources (muons). Here, we use an electron linear accelerator (linac) as an on-demand high-energy particle source to study deleterious effects on a multi-qubit transmon system. The linac provides a pulsed, microsecond burst of ~20 MeV electrons that are redirected at a modified dilution refrigerator. We show how single electron collisions with the quantum chip mimic the energy deposition from a typical cosmic ray muon and cause correlated qubit errors. The error dynamics of individual qubits and the system as a whole can be easily and quickly extracted due to the on-demand nature of our radiation source. Though radiation-induced quasiparticle tunneling primarily results in transient relaxation errors, this experimental scheme also reveals excitation and frequency detuning errors. We also present differences in error behavior due to qubit design and state preparation. This new facility enables the systematic study of novel qubit designs and packaging techniques for radiation-induced error mitigation.