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arXiv · 2011.02054

Floquet exceptional contours in Lindblad dynamics with time-periodic drive and dissipation

John Gunderson·Jacob Muldoon·Kater W. Murch·Yogesh N. Joglekar
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Abstract

The 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 new, potentially preferred route to accessing exceptional points in the transient dynamics towards the Lindblad steady state.

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John Gunderson, Jacob Muldoon, Kater W. Murch, Yogesh N. Joglekar. 2020-11-03. Floquet exceptional contours in Lindblad dynamics with time-periodic drive and dissipation. https://doi.org/10.1103/physreva.103.023718

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