Energy Transfer in a System of Coupled Superconducting Qubits

We investigate energy transfer in a system of three capacitively coupled transmon qubits. Qubits 1 and 2 interact with a coplanar-waveguide transmission line, through which the system is energized, and qubit 3 with a large decay rate resonator through which its Purcell-limited decay is measured. We study the power spectral density of microwave radiation emitted back into the transmission line and into the resonator in dependence on various system parameters and interpret the results.