It may sound like science fiction, but it’s not: Scientists have created the first time crystal, using a chain of ions. Just as a standard crystal repeats in a regular spatial pattern, a time crystal repeats in time, returning to a similar configuration at regular intervals.
“This is a remarkable experiment,” says physicist Chetan Nayak of Microsoft Station Q at the University of California, Santa Barbara. “There is a ‘wow factor.’”
Scientists at the University of Maryland and the University of California, Berkeley created a chain of 10 ytterbium ions. These ions behave like particles with spin, a sort of quantum mechanical version of angular momentum, which can point either up or down. Using a laser, the physicists flipped the spins in a chain of ions halfway around, from up to down, and allowed the ions to interact so that the spin of each ion would influence the others. The researchers repeated this sequence at regular intervals, flipping the ions halfway each time and letting them interact. When scientists measured the ions’ spins, on average the ions went full circle, returning to their original states, in twice the time interval at which they were flipped halfway.
This behavior is sensible — if each flip turns something halfway around, it takes two flips to return to its original position. But scientists found that the ions’ spins would return to their original orientation at that same rate even if they were not flipped perfectly halfway. This result indicates that the system of ions prefers to respond at a certain regular period — the hallmark of a time crystal — just as atoms in a crystal prefer a perfectly spaced lattice. Such time crystals are “one of the first examples of a new phase of matter,” says physicist Norman Yao of UC Berkeley, a coauthor of the new result, posted online September 27 at arXiv.org.
To read more, click here.