Interpreting Liouvillian Eigenmodes: Quantized Orbits in Dissipative Systems
Ashlin V Thomas, Felix Fritzsch, Masudul Haque +1 more
In closed quantum dynamics, energy eigenstates represent physical excitations which, for systems with a classical limit, localize on quantized orbits in phase space. Such a picture is lacking in open systems: Liouvillians have distinct right and left eigenstates that decay with time and are difficult to interpret. We recover a physical correspondence by introducing a gauge-invariant quasiprobability measure combining right and left eigenstates that interprets a Liouvillian mode as a set of coherences, allowing one to visualize the modes as quasiprobability distributions in a ``doubled'' phase space. Using this measure we show that, remarkably, a damped oscillator retains its quantized ``orbits'' for a large class of linear and nonlinear loss, with measurable signatures. A thermal bath broadens these orbits, similar to energy levels, leading to a characteristic multistage relaxation. This provides an experimentally accessible open-system analog of the eigenstate-orbit correspondence underlying semiclassical quantization. For quadratic systems, our results yield dissipative analogs of invariant tori - a central concept in Hamiltonian systems.
quant-pharXiv:2606.20271•Jun 19, 2026•0 citations