Just as a crystal consists of a regular array of particles repeated in space, so a space-time crystal should consist of a regular pattern of particles that also repeats cyclically over time. Now, Xiang Zhang at the University of California, Berkeley, and his team have published the first proposal for an experiment that could realize this abstract notion.

The authors' idea is to trap a ring of cold ions in a magnetic field so that they adopt a regular arrangement and then rotate in their lowest energy state, thereby creating temporal repetition. Such a device might be able to store quantum information, and could thus have applications in quantum computing, the researchers say.

Phys. Rev. Lett. 109, 163001 (2012)