Localized infrared light source of quasiparticles in transmon qubits

Improving the capabilities of superconducting circuits as quantum processors relies on furthering our understanding of their decoherence mechanisms. For example, high energy radiation can break Cooper pairs and create so-called Bogoliubov quasiparticles, which can lead to relaxation and decoherence of quantum states. In general, it is believed that the decoherence of a superconducting qubit is proportional to the density of quasiparticles in the device, motivating efforts to avoid any sources of stray electromagnetic radiation that could induce these excitations. Here we present an experiment that takes the opposite approach and controllably introduces infrared light in the vicinity of a 3D aluminum transmon. We use a pulsed telecom band laser as a spatially and temporally localized source of quasiparticles. We show how the absorption of light modifies the lifetime of the transmon and demonstrate a typical recovery time for the qubit that is one order of magnitude faster than in previous experiments with microwave-induced quasiparticles [1]. Our results also have useful implications for the transduction of quantum information between the microwave and telecom domains.