Time Crystals Explained | Answers With Joe

I recently did a live stream about the subject of time crystals, but there was much more to talk about. So here you go.

When you hear the term Time Crystals, you immediately think of something cool and sci-fi like something from Doctor Who, but spoilers… Not so much. That doesn’t mean they’re not interesting, they’re super-interesting, just… Not what powers a Tardis. The explanation that we keep hearing is that time crystals are crystals whose atomic structures repeat in space and in time. Like the reason crystals become crystals is the way the atoms of particular elements bond with each other in certain patterns that repeat over and over again. That’s repeating in three dimensions. But time crystals repeat in four dimensions. They also repeat in time. Time as a construct relies on cause and effect, one thing preceding the other, always working toward equilibrium, or a zero energy state. If you have a row of atoms repeating in a crystal, and you send energy along that line, it will pass through one atom, then another, all the way down until the system returns to equilibrium, or zero point energy. But with time crystals, atoms are connected through quantum entanglement in repeating patterns so that atoms down the chain would feel the effect before the cause, so energy sent down the line would repeat over and over again, making it impossible to return to equilibrium. That’s why they’re also called non-equilibrium matter. And that’s also why you hear so many people describe it as jello that never stops jiggling. Because even in its lowest energy state, the atoms never stop moving. Now, one question I got asked a lot in the livestream was if this breaks the law of conservation of momentum. And the answer is… Yes. It very does. Which is why this was such a big deal. And it’s something I don’t think I fully grasped in the livestream. There’s an even more fundamental law of the universe known as time translation symmetry which states that the laws of physics must work the same way everywhere at all times. And if you have matter that moves without using any energy, that sounds a lot like the laws of physics working differently. But when Nobel-prize winning physicist Frank Wilczek introduced the idea in 2012, he proposed a loophole. He stated that if symmetry is broken explicitly, then the laws of nature do not have symmetry anymore. But he argued that there’s such a thing as spontaneously broken symmetry, which means that the laws of nature still has symmetry, but nature chooses a system that does not. In other words, if the laws of nature allow these atoms to arrange in this way, then they’re still being loyal to the laws of nature. Regardless, the idea is tantalizing enough that teams of researchers have been working on it since then, and just this year, two different teams announced that they’d pulled it off. The first team from the University of Maryland, lead by Chris Monroe, took 10 ytterbium atoms and used one laser to create an electromagnetic field around the atoms, which entangled the various atoms, before blasting it with a second laser that jostled the atoms. And as predicted, once the energy was introduced, it never stopped. In fact, it started jiggling at a different rate than the laser introduced into it. This was a non-equilibrium state. But the team at Harvard did it a totally different way, by using molecules from nitrogen vacancy centers, which are tiny flaws in diamonds. But the fact that they used such different methods is encouraging, it may be that these aren’t that hard to produce and there may be hundreds of ways to do it. Which is great because there really are some cool applications for this. First of all, it makes the perfect timepiece. If you have a type of matter that oscillates at a specific frequency naturally, that’s about as accurate as you can get. But the most exciting application is for quantum computing because the entangled atoms in the atomic structure could allow stable qubits of information to be stored. Now, as always, we have to take these kinds of announcements with grains of salt. These kinds of major discoveries often have ways of falling apart under scrutiny, so we’ll have to wait and see how this holds up to peer review and future experimentation, but still… pretty exciting stuff.