Experimental Characterization of a Modular Dissipator for On-Demand Cavity Cooling*

In superconducting qubits, spurious thermal photons in readout cavities are a major source of dephasing error. Properly thermalizing these cavities often involves putting large amounts of attenuation on the microwave lines, suppressing the speed of operations, causing excess cryostat heating, and reducing readout fidelity. We use an alternative approach where dissipation is introduced on-demand to cool a cavity. We have designed and fabricated a hybrid device consisting of a fixed frequency logical qubit with a readout cavity parametrically coupled to a lossy flux-tunable "dissipator," which can induce the removal of thermal photons from the cavity into the environment on-demand. Theoretical and numerical results have already validated the efficacy of this driven dissipative cooling. In this presentation, we show measurement techniques for characterizing the effectiveness of this device, and discuss the experimental results demonstrating the effects of dissipative cooling on the logical qubit in this design.