Speaker
Description
Superconducting qubits are susceptible to transient energy deposition arising from cosmic rays and environmental radioactivity. High-energy phonons generated by particle interactions in the qubit chip substrate can create quasiparticles that temporarily degrade qubit coherence.
We investigate the qubit response under controlled irradiation using a proximal Radium-224 source. To identify radiation-induced events, we develop and implement a robust data-selection protocol capable of discriminating signal events from background noise. The observed event rate scales with source activity and exhibits an exponential decay consistent with the radioactive decay of Radium-224.
In addition, we expose the qubit to purely thermal pulses generated by a silicon heater and to optical pulses from an LED source, with the aim of characterizing the device response to different types of energy deposition.
Furthermore, we explore the use of multiple qubits as phonon-mediated detectors, aiming to maximize the signal-to-noise ratio through simultaneous readout. Finally, we correlate the qubit response with that of a well-established cryogenic sensor, namely a neutron transmutation doped (NTD) germanium thermistor, capable of reconstructing the energy deposited in the substrate.
We present recent results and outline future prospects for the development of radiation-resilient quantum devices and phonon-based detection techniques.
