You’re probably quite familiar with the basic states of matter—solid, liquid, gas—that fill everyday life on Earth. But those three different sorts of matter that each look and act differently aren’t the whole of the universe—far from it. Scientists have discovered (or created) dozens of more exotic states of matter, often bearing mystical and fanciful names: superfluids, Bose-Einstein condensates, and neutron-degenerate matter, to name a few.
In the last few years, physicists around the world have been constructing another state of matter: a “time crystal.” If that seems like B-movie technobabble, it’s technobabble no longer. Using a quantum computer, a few researchers have created a time crystal that, they think, firmly establishes time crystals in the world of physics.
The researchers haven’t yet formally published their research, but last month, they posted a preprint (a scientific paper that has yet-to-be peer-edited) on the website ArXiV.
So what exactly is a time crystal? It might sound like the critical component that makes a time machine tick, some sort of futuristic power source, or perhaps an artifact of a lost alien civilization. But, to scientists, a time crystal is actually something more subtle: a curiosity of the laws of physics.
What defines any bog-standard crystal—such as a diamond, an emerald, or even an ice cube—is that the crystal’s atoms are somehow arranged in repeating patterns in space. There’s three dimensions of space—and a fourth dimension, time. So physicists wondered if a crystal’s atoms could be arranged in repeating patterns in time.
In practice, that works something like this. You create a crystal whose atoms start in one state. If you blast that crystal with a finely tuned laser, those atoms might flip into another state—and then flip back—and then flip again—and so forth, all without actually absorbing any energy from the laser.
If you step back, what you’ve just created is a state of matter that’s perpetually in motion, indefinitely, without taking in any energy.