Nonlinear two-level dynamics of quantum time crystals

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. Recent work has reported a realization of a time crystal in the form of the Bose-Einstein condensate of magnons in superfluid He-3. Here, the authors study the dynamics of a pair of such quantum time crystals and show that it closely resembles the evolution of a two-level system, modified by nonlinear feedback.

Automated summary

Time crystals are macroscopic quantum systems that exhibit periodic motion in their ground state. Experimental studies show that time crystals formed by spin-wave quasiparticles can provide detailed insights into quantum-coherent interactions. The dynamics of such quantum time crystals closely resemble that of a two-level system, influenced by nonlinear feedback mechanisms.