Anomalous Temperatures of Superconducting Qubits

We present qubit temperature measurements on several superconducting transmon qubits coupled to compact resonators. By addressing multiple transitions of the artificial atom and cavity system, we measured the temperature as a function of qubit and cavity frequency and cavity Q. For high cavity Q and large detuning, qubit temperatures were found to be greater than 120mK, well in excess of the dilution refrigerator base temperature of 15mK. This unanticipated effect can be explained by the decoupling of the qubit to the cold load damping the cavity. We will present our attempts to produce lower qubit temperatures with additional filtering and dynamical cooling experiments.