Nonlinear two-level dynamics of quantum time crystals.

Autti, S; Heikkinen, P J; Nissinen, J; Mäkinen, J T; Volovik, G E; Zavyalov, V V; Eltsov, V B · Nat Commun · 2022

basic_science · Level V

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Abstract

A time crystal is a macroscopic quantum system in periodic motion in its ground state. In our experiments, two coupled time crystals consisting of spin-wave quasiparticles (magnons) form a macroscopic two-level system. The two levels evolve in time as determined intrinsically by a nonlinear feedback, allowing us to construct spontaneous two-level dynamics. In the course of a level crossing, magnons move from the ground level to the excited level driven by the Landau-Zener effect, combined with Rabi population oscillations. We demonstrate that magnon time crystals allow access to every aspect and detail of quantum-coherent interactions in a single run of the experiment. Our work opens an outlook for the detection of surface-bound Majorana fermions in the underlying superfluid system, and invites technological exploitation of coherent magnon phenomena - potentially even at room temperature.