A new state of matter known as time crystals which appears to suspend the laws of thermodynamics almost indefinitely, a series of new experiments suggest. The time crystals are essentially a collection of atoms that are far apart but still interacting with one another. At a certain frequency, this form of matter keeps “ticking” indefinitely, without heating up or creating entropy—the natural state of disorder that exists in the universe. This new matter joins a group of other exotic states of matter such as superconductors, quantum spin liquids, and superfluids.
“We have found a new phase of matter,” Soonwon Choi, co-author of the study and a theoretical physics graduate student at Harvard, notes. “It’s something moving in time while still stable.”
This newfound state is more than fascinating—it could also ensure that quantum computers don’t lose information, Choi adds.
The idea of a time crystal was first introduced by physicist Frank Wilczek in the journal Physical Review Letters in 2012. In his study, Wilczek suggested there could be a form of matter that spontaneously breaks “time invariance.” The concept of time invariance is, to put it simply, doing something now will produce the same result as doing the same thing one minute from now (all other conditions being equal). In Wilczek’s proposal, quantum interactions create a state of matter that oscillates in time, breaking that rule. Doing something with that matter now would produce different results from doing the same thing 1 minute from now. So how, exactly, does that work?
Study co-author Norman Yao asks us to think about this like two people holding a jump rope and swinging it for a third person who is jumping. In ordinary states of matter, if the rope makes a circle every second, the person must jump every second. In a time crystal, the jumper could lift his or her feet every other time the rope hits the ground without ever getting entangled in the rope.
The study that followed up on Wilczek’s idea was able to demonstrate that time crystals could not exist in thermal equilibrium (complying with a fundamental principle of thermodynamics). However, researchers showed that time crystals could exist in dynamic states when systems are changing quickly and haven’t yet reached equilibrium. Earlier this year, Yao and his team developed a theoretical paper that identified key signatures of a time crystal, laying out an experimental way to prove their existence. Independently, Choi and colleagues set out to create such a crystal in the lab.
In a pair of studies published in Nature, the researchers showed that time crystals can actually exist in very different systems.
Choi and his colleagues used a diamond filled with 1 million nitrogen-vacancy color centers; spots where nitrogen atoms have replaced carbon atoms, leaving an empty space in the lattice. The nitrogen and the empty space can act together as if they are tiny particles with spins. Using lasers and microwave radiation, the team then periodically pulsed these nitrogen vacancies, which oscillated with a frequency that was half of the frequency of the radiation aimed at them.
In a second and separate experiment, Yao and his colleagues trapped 14 ions of ytterbium using laser beams. Using tightly focused laser beams, they manipulated the ions’ spins. Once again, the material acted like a time crystal, oscillating at half the driving frequency. Despite significant energy being pumped into the system, the material did not heat up, indicating that thermodynamics did not come into play.
According to Yao, the new findings also show that the time crystaldoes not need to be perfectly isolated from heat and entropy to show its repeating-in-time properties. It could be very easy to generate these exotic states of matter, and they have the potential to suspend the laws of physics indefinitely.
Interestingly, these time crystals don’t break the laws of thermodynamics; they just suspend them for the duration of the experiment.
Source: Live Science