Observation of a discrete time crystal
In 2012, Nobel-prize winning physicist Frank Wilczek, a professor at the Massachusetts Institute of Technology, proposed something that sounds pretty strange. It might be possible, Wilczek argued, to create crystals that are arranged in time instead of space. The suggestion prompted years of false starts and negative results that ruled out some of the most obvious places to look for these newly named time crystals.
Now, five years after the first proposal, a team of researchers led by physicists at the Joint Quantum Institute and the University of Maryland have created the world's first time crystal using a chain of atomic ions. The result, which finally brings Wilczek's exotic idea to life, was reported in Nature on March 9.
To create their time crystal, researchers activated three types of laser-driven behavior in a chain of ten ytterbium ions. First, each ion was bombarded with its own individual laser beam, flipping an internal quantum property called spin by roughly 180 degrees with each pulse. Second, the ions were induced to interact with each other, coupling their internal spins together like two neighboring magnets. Finally, random disorder—essentially noise—was sprinkled onto each ion, a feature known from previous experiments to prevent the spins from jostling and heating up the chain.
Altogether, this sequence twisted around the ions' spins, and researchers kept track of the orientation of each spin after many repetitions of the sequence. When all three laser-driven behaviors were turned on, the spins of each ion synced up, and they would rhythmically return to their original direction at half the speed of the laser sequence.
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