Bath engineering of a fluorescing artificial atom with a photonic crystal

A quantum emitter decays due to vacuum fluctuations at its transition frequency. By virtue of the entwined nature of dissipation and fluctuations, this process can be controlled by engineering the impedance of the environment. In our experiment, a transmon qubit and a microwave photonic crystal are respectively the emitter and the engineered vacuum environment. The photonic crystal is realized by a step-impedance transmission line which, akin to a Purcell filter, structures the electromagnetic density of states by suppressing vacuum fluctuations over a frequency band. If the emitter's transition frequency is on the photonic band edge, the non-Markovian structured environment allows for drive and dissipation to produce non-trivial steady states.