Speaker
Description
In this presentation we describe ongoing work at NIST with circuits that combine qubit arrays and superconducting transition-edge sensors (TESs) on the same silicon substrate. The TESs are intended to serve two purposes. Because the TESs are fabricated directly on the silicon, they are sensitive to phonons created in the substrate by background radiation and thus they provide an on-chip, spectroscopic detection capability for background events. In addition, the bias power in the TESs is automatically reduced by negative electrothermal feedback when they are excited, providing a virtual thermal conductance between the TES and the thermal bath. The circuits are designed so that this virtual conductance is significant compared to the physical conductance between the silicon substate and the bath. As a result, the TESs are expected to stabilize the thermal environment of the qubit array after a background event and mature implementations of the circuit could provide protection from disruptive correlated decoherence events. Having recently fabricated devices with both working TESs and qubits, we are now characterizing them. Ongoing measurements include studies of the electromagnetic interactions between TESs and qubits, extraction of the thermal conductances between the TES, chip, and bath, and demonstrations of radiation detection and energy removal by the TESs. We report progress on these varied measurements.