Discrete time crystal physics and related phases may be exploited in future quantum technologies.
While the periodic spatial arrangement of atoms in a crystal (like salt) has been known for a century, the concept of a “discrete time crystal” (DTC) is less than 5 years old. The DTC is an unusual out-of-equilibrium state of matter that may be induced by periodic driving of an interacting quantum spin system. In 2017, two experiments reported a key DTC signature: for long enough interaction times, the system’s response becomes rigidly locked to half of the driving frequency. In 2018, using nuclear magnetic resonance (NMR), we reported finding this DTC signature in the most unexpected system to date: a clean, ordered crystal. This challenges the paradigm that the DTC arises from many-body localization. In addition, a “DTC echo” experiment revealed hidden coherence in the system.
