Accessing the role of quantum jumps on non-Hermitian dynamics of a superconducting qubit*

We study the dynamics of a dissipative transmon superconducting qubit whose dissipation comes into two parts: a fast coherent nonunitary dissipation (energy loss) and a slow decoherence due to quantum jumps within the qubit. We observe that the coherence damping rate is enhanced near the exceptional point. Together with the effect of non-Hermitian gain/loss, the decoherence also leads to breakdown of adiabatic evolution under the slow-driving limit. Our study shows the critical role of quantum jumps in generalizing the applications of classical non-Hermitian systems to open quantum systems from sensing to control.