Time Crystals Created, Suspending Laws of Physics
"We have found a new phase of matter," said study co-author Soonwon Choi, a theoretical physics graduate student at Harvard University. "It's something moving in time while still stable." [The 18 Biggest Unsolved Mysteries in Physics]
While the newfound state of matter is fascinating in itself, it could also pave the way for quantum computers that don't lose information, Choi said.
Physicist Frank Wilczek first proposed the idea of a time crystal in the journal Physical Review Letters in 2012. In that study, he suggested a form of matter that spontaneously breaks "time invariance," a fundamental symmetry in time. The concept of time invariance dictatesthat doing something now would produce the same result as doing the same thing, for example, 1 minute in the future (all other conditions being equal).
In Wilczek's conception, however, the quantum interactions among particles, such as ions or subatomic particles, could create a state of matter that oscillates repeatedly in time, just as a crystal has a structure that repeats in space. That means that if the matter oscillated with a period of 2 minutes, doing something with that matter now would produce different results than doing the same thing 1 minute from now. [Photos: Exotic Time Crystals Created in the Lab]
To understand what this means, imagine two people holding a jump rope and swinging it for a third person doing the jumping. In ordinary states of matter, if the rope makes a circle every second, the person must jump every second. But in a time crystal, it is as if the jumper lifts his or her feet every other time the rope hits the ground, and yet somehow keeps time and does not get entangled in the rope, said study co-author Norman Yao, a physicist at the University of California, Berkeley, who earlier this year developed a theoretical framework for testing time crystals.
More recently, follow-up work that built on Yao's framework showed that time crystals could not exist in thermal equilibrium. (A fundamental principle of thermodynamics is that two objects in contact will eventually wind up at the same temperature at the steady state, or thermal equilibrium, of the system.) But soon after, researchers showed that time crystals could exist in dynamic states, when systems are changing quickly and haven't yet reached thermal equilibrium.
Earlier this year, Yao, with Andrew Potter, a physicist at the University of Texas at Austin, and colleagues, developed a theoretical paper that identified key signatures of a time crystal. That paper predicted what would happen when a such a crystal melts into a more humdrum state of matter, and laid out an experimental way to prove the existence of time crystals. Independently, Choi and colleagues developed their own idea for a method of demonstrating the existence of time crystals, and then set out to create such a crystal in the lab.
In a pair of studies published today (March 8) in the journal Nature, the researchers showed that time crystals can exist in very different systems.