Thursday, March 09, 2017

Time Crystal

This is quite an astonishing feat. It was only back in 2012 that Frank Wilczek proposed the possibility of a "time crystal", where a certain symmetry repeats in time, rather than in space. This was followed soon enough by a formal proposal for such a crystal. And now, we appear to have two experimental evidence.[1,2]

Potter is part of the team led by researchers at the University of Maryland who successfully created the first time crystal from ions, or electrically charged atoms, of the element ytterbium. By applying just the right electrical field, the researchers levitated 10 of these ions above a surface like a magician’s assistant. Next, they whacked the atoms with a laser pulse, causing them to flip head over heels. Then they hit them again and again in a regular rhythm. That set up a pattern of flips that repeated in time.

Crucially, Potter noted, the pattern of atom flips repeated only half as fast as the laser pulses. This would be like pounding on a bunch of piano keys twice a second and notes coming out only once a second. This weird quantum behavior was a signature that he and his colleagues predicted, and helped confirm that the result was indeed a time crystal.

Like I said, this is quite a feat to come up with a scheme to be able to create and test this.


[1] J. Zhang et al., Nature 543, 217 (2017).
[2] S. Choi et al., Nature 543, 221 (2017).

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