Developing active protection of superconducting qubits from background radiation with on-chip transition-edge sensors

Excess quasiparticles are widely observed in superconducting devices and are known to be a source of decoherence in superconducting qubits. We are developing qubits with additional robustness to quasiparticle excitations by adding features to actively suppress energy transients and to detect quasiparticle generation sources such as cosmic rays. Our approach uses the negative electrothermal feedback of transition edge sensors (TESs) to both remove excess energy and serve as on-chip detectors.

In this talk, we present the design and measurements of a chip with co-fabricated transmon qubits and AlMn TESs. We characterize the performance of the qubits and demonstrate simultaneous operation of the qubits and TESs. We investigate how energy added to the chip, for example through on-chip heating, can be actively removed by biasing the TES in the transition. Further, we discuss how the TESs can be used for spectroscopic detection of background events that impact the qubit coherence through concurrent measurements of the TESs and qubits.