Speaker
Description
Correlated error bursts causing decoherence in superconducting qubits have been detrimental to quantum error correction schemes, with recent work by Google showing approximately once per hour correlated bursts in their qubits. Over the past decade, it has been shown that ionizing radiation contributes to this effect, with cosmic rays being commonly identified. However, with advent of bandgap-engineering, the reduced sensitivity to energy depositions in a substrate implies that only the highest energy events should be the problem, but it has not yet been definitively shown which type of ionizing radiation is the culprit.
At PNNL, we have fabricated custom alpha sources from the Po-210 isotope with activities of 10 or less decays per minute. These sources have been placed with direct line of sight to a 4 cm$^2$ sapphire substrate patterned with an array of nine superconducting detectors (MKIDs) operating at 10 mK. We have measured the multiplexed response of these resonators to different sources of ionizing radiation, for which alphas demonstrate a specific signature when interacting with the substrate via high-amplitude, highly correlated events. In this talk, we will discuss these results as they pertain to superconducting qubits, as well as outline the next steps in fully disentangling signatures due to different types of ionizing radiation.
