What are time crystals and why will they be important in the future?

Time crystals are being described as a new phase of matter. Ordinary crystals, like diamonds and quartz, have an atomic structure that repeats in space, however, these newly discovered crystals also have a structure that repeats in time.

“Let’s start with a thought experiment.” Dr Von Keyserlingk says. “Imagine partly filling a box with many coins, and those coins have two sides: heads or tails. If a coin within the box is heads up, I’ll say it’s pointing upwards, and if that coin is heads down, I’ll say it’s pointing downwards.”

“If I was to shake that box a few hundred times, you wouldn’t be very surprised if I told you that after shaking the box, approximately half of the coins will be pointing up and the other pointing down. If I had a box which had most coins pointing up, after I shook that box a few million times, the system would probably forget that most of the coins were initially facing up, so, half of the coins will be pointing up and the other pointing down. Time crystals are an example of a system, a quantum mechanical example of a system for which this doesn’t hold.”

“In a time crystal, instead of having coins, we have things called spins – intrinsic quantum mechanical objects that behave similar to coins in that they can point up or down. Within a time crystal, if the spins were initially pointing up, then after a million shakes, they all point up again. After a million and one shakes, they all point down. Time crystals are special as they remember what the system was doing originally, and exhibit this regular, even odd, pattern of behaviour in time as you continue to shake the box.”

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