“Every particular in nature, a leaf, a drop, a crystal, a moment of time is related to the whole, and partakes of the perfection of the whole.” -Ralph Waldo Emerson
When you think of crystals, you likely think of an interlocked, repeating lattice of atoms or molecules. That’s exactly what a conventional crystal is. But recently, there’s been an exciting new idea, first proposed by Frank Wilczek in 2012: that it would be possible to create a time crystal, an entirely new class of system.
Phase diagram of the discrete time crystal as function of Ising interaction strength and spin-echo pulse imperfections. Image credit: Norman Y. Yao, Andrew C. Potter, Ionut-Dragos Potirniche, Ashvin Vishwanath.
You might think that this means that time — rather than atoms or molecules — are crystallized, but that’s not quite right. Instead, particles that are coupled together would spontaneously return to the same state, breaking the symmetry known as time-translation invariance. A method for building one was proposed just last year, and already two independent teams have made it work!
Ten yttrium atoms with entangled electron spins, as used to first create a time crystal. Image credit: Chris Monroe/University of Maryland.