A comparative study of energy sensing schemes for qubit-based detectors

The interaction between superconducting qubits and quasiparticles that tunnel across the Josephson junction can be leveraged to detect quasiparticle-generating energy depositions, making them promising platforms for sub-eV phonon/photon sensing. Each tunneling event flips the qubit charge parity and may also result in energy transfer between the qubit and the quasiparticle. We present a comparative study of the sensitivities of various energy sensing methods that detect energy depositions by monitoring the quasiparticle tunneling rate. The charge sensitivity of superconducting qubits serves as another channel through which energy depositions can be observed. For this, we present a study on the dynamics of the offset charge states of a tantalum qubit on a sapphire substrate, as observed through multilevel qudit measurements.