(Phys.org) —There has been a lot of talk recently about the possibility of building what has come to be known as a time crystal. In February 2012, Frank Wilczek originally proposed the idea that under certain conditions, physical structures can move in a repeating pattern without expending any energy. Last June, a group of researchers at Berkeley proposed a time crystal could be realized as a persistently rotating ring of charged atoms. Unfortunately a problem with that approach was pointed out by Patrick Bruno, who noted that to be a time crystal, an object must exhibit perpetual motion in its lowest energy state—the ground state. Commenting in Physical Review Letters in March, Bruno showed that the particular example described by Wilczek was actually one of a system in an excited state, and therefore not a time crystal. Taking advantage of recent breakthroughs in the construction of low noise ion traps, Berkeley researchers now plan to build an ion trap that will satisfy the critics.
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