Nonlinear two-level time crystal dynamics

Time crystals are a novel phase of condensed matter, characterised by continuous, repeating motion in their quantum ground state. In our experiments, we explore this new phase using magnetic quasiparticles in the superfluid universe of 3He: We observe the formation of a quantum time quasicrystal and its transformation to a superfluid time crystal - a time supersolid. We then bring two superfluid time crystals to touch each other, creating a time crystal two-level system. The two level system is characterised by AC Josephson/Rabi population oscilltions, a level crossing between the time crystals, and Landau-Zener population transfer between the levels. These ground-breaking experiments substantiate the theoretical excursion started by Frank Wilczek, and provide a novel, magnetic building block for quantum devices and quantum information processing - potentially even at room temperature.

This work has been supported by the European Research Council (Grant Agreements 694248 and 824109), by the UK EPSRC (EP/P024203/1, EP/W015730/1), the Jenny and Antti Wihuri foundation, and the Väisälä foundation of the Finnish Academy of Science and Letters. We acknowledge the computational resources provided by the Aalto Science-IT project.