4 ms·

Crystallization of time seems like a misnomer to me. Aren't they continually adding laser energy to the system to maintain the "crystal" state? Doesn't crystall

by daveguy 10y ago

Crystallization of time seems like a misnomer to me. Aren't they continually adding laser energy to the system to maintain the "crystal" state? Doesn't crystallization imply a stable state resistant to external energy sources rather than dependent on them?

reptation 10y ago
I tend to agree, but had a lot of trouble understanding the article (I studied different branch of physics). I think this is the key: "The recipe was incredibly complex, but just three ingredients were essential: a force repeatedly disturbing the particles, a way to make the atoms interact with each other and an element of random disorder... More than that, the researchers found that even if they started to flip the system in an imperfect way, such as by slightly changing the frequency of the kicks, the oscillation remained the same."
SomeStupidPoint 10y ago
I think "the quest to crystalize in time" would be a better title.
logfromblammo 10y ago
First, imagine a halite crystal. In halite, ions of sodium+ and chloride- are stacked in an orderly fashion. If you orient the crystal correctly, you can put your mental finger on a sodium ion, and move it in the x dimension, and it will alternate NaClNaClNaCl-.... You can move your mental pointer in any of the spatial dimensions, and the state you encounter will alternate between the two component ions. To turn the halite crystal into a (hypercubic) time crystal, you would need to move your mental pointer in the time dimension and see the ions alternate, just as they did in the spatial dimensions. You could potentially do this by causing those ions to spontaneously transmute into each other, in a cyclic fashion. Or you could oscillate the crystal at just the right orientation and speed. But both of those are currently beyond our technical capabilities. In theory, if ionic attraction behaved similarly in the time dimension as in spatial dimensions, there will be a particular resonant frequency of oscillation that would indicate that the halite had gone from a cubic spatial crystal to a hypercubic spacetime crystal. But that oscillation speed is likely associated with a temperature that would destroy the spatial crystal by melting it. Too bad. You probably can't turn a halite crystal into a spacetime crystal. If you had one already, it might be metastable enough to not melt, but as they say, you can't get there from here. But we can flip the spin of an electron. So instead of making an ionic crystal, you make an electron spin crystal in an existing molecular lattice structure. Then you pulse a laser at it to make all of the spins flip. In that situation, the crystal structure lines up to ensure that the spin-flips occur at a particular rate. If you stop kicking at it, it stops being a crystal, just like going past the physical boundary of an ionic crystal. If you add more sodium and chloride to halite, you can make the crystal grow in spatial dimensions. Adding more laser energy to a spin crystal causes it to grow in the temporal dimension. And like adding the ions, you don't have to line them up exactly before letting them go. You just dump them, and the crystal orders itself. So those sort-of-random kicks give enough extra energy that the time crystal can keep growing in the time dimension. If you stop kicking, the crystal might have enough internal "conductiveness" of that spin-flip energy to keep flipping by itself for a while just from the previous kicks you gave it, or even the ones you haven't given it yet. But crystals have finite boundaries. Eventually, you get to the end of the crystal in the temporal dimension, and it stops flipping. But we have no idea how long you will have to watch it before it stops, since we don't know exactly how time crystals work.

by daveguy 10y ago

reptation 10y ago

I tend to agree, but had a lot of trouble understanding the article (I studied different branch of physics). I think this is the key: "The recipe was incredibly complex, but just three ingredients were essential: a force repeatedly disturbing the particles, a way to make the atoms interact with each other and an element of random disorder... More than that, the researchers found that even if they started to flip the system in an imperfect way, such as by slightly changing the frequency of the kicks, the oscillation remained the same."

SomeStupidPoint 10y ago

I think "the quest to crystalize in time" would be a better title.

logfromblammo 10y ago

First, imagine a halite crystal. In halite, ions of sodium+ and chloride- are stacked in an orderly fashion. If you orient the crystal correctly, you can put your mental finger on a sodium ion, and move it in the x dimension, and it will alternate NaClNaClNaCl-.... You can move your mental pointer in any of the spatial dimensions, and the state you encounter will alternate between the two component ions. To turn the halite crystal into a (hypercubic) time crystal, you would need to move your mental pointer in the time dimension and see the ions alternate, just as they did in the spatial dimensions. You could potentially do this by causing those ions to spontaneously transmute into each other, in a cyclic fashion. Or you could oscillate the crystal at just the right orientation and speed. But both of those are currently beyond our technical capabilities. In theory, if ionic attraction behaved similarly in the time dimension as in spatial dimensions, there will be a particular resonant frequency of oscillation that would indicate that the halite had gone from a cubic spatial crystal to a hypercubic spacetime crystal. But that oscillation speed is likely associated with a temperature that would destroy the spatial crystal by melting it. Too bad. You probably can't turn a halite crystal into a spacetime crystal. If you had one already, it might be metastable enough to not melt, but as they say, you can't get there from here. But we can flip the spin of an electron. So instead of making an ionic crystal, you make an electron spin crystal in an existing molecular lattice structure. Then you pulse a laser at it to make all of the spins flip. In that situation, the crystal structure lines up to ensure that the spin-flips occur at a particular rate. If you stop kicking at it, it stops being a crystal, just like going past the physical boundary of an ionic crystal. If you add more sodium and chloride to halite, you can make the crystal grow in spatial dimensions. Adding more laser energy to a spin crystal causes it to grow in the temporal dimension. And like adding the ions, you don't have to line them up exactly before letting them go. You just dump them, and the crystal orders itself. So those sort-of-random kicks give enough extra energy that the time crystal can keep growing in the time dimension. If you stop kicking, the crystal might have enough internal "conductiveness" of that spin-flip energy to keep flipping by itself for a while just from the previous kicks you gave it, or even the ones you haven't given it yet. But crystals have finite boundaries. Eventually, you get to the end of the crystal in the temporal dimension, and it stops flipping. But we have no idea how long you will have to watch it before it stops, since we don't know exactly how time crystals work.