Time Crystals

[geordief]

Seems like an interesting story

 

" Instead of regularly repeating rows of atoms, a time crystal would exhibit regularly repeating motion."

 

https://www.newscientist.com/article/2119804-worlds-first-time-crystals-cooked-up-using-new-recipe/

 

http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.118.030401

[TheVat]

https://www.quantamagazine.org/first-time-crystal-built-using-googles-quantum-computer-20210730/

Getting around the second law of thermo is pretty cool. 

[swansont]

Nobody has gotten around the 2nd law, which states that entropy of an isolated system can’t decrease, and it hasn’t. 

Usually it increases, and in this case it hasn’t, or at least that’s apparently the case.

[joigus]

I totally concur with @swansont that entropy can never decrease in closed systems, and the next best thing is a system that keeps it constant, which is what this system seems to be.

I assume --and correct me if I'm wrong, Swansont-- that the moment you wanted to amplify the signal or involve any circuitry in any way, the constant-entropy condition would be lost. I suppose it would be like a phenomenally efficient chronometer, rather than your regular timepiece.

[swansont]

10 hours ago, joigus said:

I totally concur with @swansont that entropy can never decrease in closed systems, and the next best thing is a system that keeps it constant, which is what this system seems to be.

I assume --and correct me if I'm wrong, Swansont-- that the moment you wanted to amplify the signal or involve any circuitry in any way, the constant-entropy condition would be lost.

 

That's already the case. The constant entropy condition is the crystal itself, and the state it's in, and ignores all of the equipment necessary to get the crystal into the state where this behavior is possible.

10 hours ago, joigus said:

I suppose it would be like a phenomenally efficient chronometer, rather than your regular timepiece.

The materials identified for these time crystals aren't very precise oscillators, and the things we use for precise clocks (i.e. atoms and ions) aren't candidates for time crystals. That doesn't preclude some candidate being identified in the future, but for now, and talk of time crystals as clocks is a nonstarter, other than as a novelty item.

Plus, as you note above, reading out the oscillations would require interacting with the crystal, and you'd lose the constant-entropy condition. There are classical analogues to this, where you have master-slave pendulums, so the high-precision pendulum is only perturbed slightly, which minimizes the compromise to its behavior.