Gunderson, JohnMuldoon, JacobMurch, Kater W.Joglekar, Yogesh N.2023-08-172023-08-172021-02-22Gunderson, J., Muldoon, J., Murch, K. W., & Joglekar, Y. N. (2021). Floquet exceptional contours in Lindblad dynamics with time-periodic drive and dissipation. Physical Review A, 103(2), 023718. https://doi.org/10.1103/PhysRevA.103.0237182469-9934https://hdl.handle.net/1805/34964The dynamics of an isolated quantum system is coherent and unitary. Weak coupling to the environment leads to decoherence, which is traditionally modeled with a Lindblad equation for the system's density matrix. Starting from a pure state, such a system approaches a steady state (mixed or otherwise) in an underdamped or overdamped manner. This transition occurs at an eigenvalue degeneracy of a Lindblad superoperator, called an exceptional point (EP), where corresponding eigenvectors coalesce. Recent years have seen an explosion of interest in creating exceptional points in a truly quantum domain, driven by the enhanced sensitivity and topological features EPs have shown in their classical realizations. Here, we present Floquet analysis of a prototypical qubit whose drive or dissipator strengths are varied periodically. We consider models with a single dissipator that generate global loss (phase damping) or mode-selective loss (spontaneous emission). In all cases, we find that periodic modulations lead to EP lines at small dissipator strengths and a rich EP structure in the parameter space. Our analytical and numerical results show that extending Lindblad Liouvillians to the Floquet domain is a potentially preferred route to accessing exceptional points in the transient dynamics towards the Lindblad steady state.enPublisher PolicyLindblad dynamicsOpen quantum systemsFloquet analysisArticle10.1103/physreva.103.023718