3 ms·

Practically speaking, this means we couldn't use the cyclic process to do work, because that would require it to have excess energy it could transfer. If a time

Practically speaking, this means we couldn't use the cyclic process to do work, because that would require it to have excess energy it could transfer. If a time crystal's periodic behavior were to spin, you couldn't use the rotation to push something. Right?

raattgift 4y ago
Right. Lowest-energy means that you can't pull energy out of a time crystal; there's no excess. Anything you try to attach to a time crystal will transfer energy into the crystal. Practically all we can do with a time crystal is to measure it with the lightest possible touch and hope it doesn't break the periodicity. (So far, afaik, the periodicity has always been broken by the measurement process's energy input). I don't know what we could do with large numbers of time crystals, though. One can't pick up a snowflake in one's bare hands and use it like a buzz saw to cut a sheet of paper (the snowflake melts on contact), but an avalanche of snowflakes can snap trees. Maybe for time crystals that rotate light a predictable amount at a given time t_x, we could create some sort of interesting lens from a large cloud of such time crystals arranged at different distances from a bright light source -- a sort of "anti-fog".
- rpz 4y ago
  If the periodicity is broken by any measurement we have been able to make so far then how do we know the periodicity is there in the first place? Just theory? If it’s not too much of a burden could you outline the proof of the existence of time crystals?
  - raattgift 4y ago
    > how do we know the periodicity is there ... Just theory? Theory guides us, but experimentally you can for example make a whole bunch of time crystals (especially straightfoward for driven time crystals, which have a period that's an integer multiple of the driver, the driving force being laser light or microwaves) with an expected set of states it cycles through, and you can test those states once per time crystal. If you reliably get the states theory predicts, that's good evidence. > could you outline the proof of the existence The excellent <https://physics.aps.org/articles/v10/5 https://physics.aps.org/articles/v10/5> and decent <https://en.wikipedia.org/wiki/Time_crystal#Experiments https://en.wikipedia.org/wiki/Time_crystal#Experiments> (the former is [5] in that wikipedia article) are good starting points, with ample references.

raattgift 4y ago

Right. Lowest-energy means that you can't pull energy out of a time crystal; there's no excess. Anything you try to attach to a time crystal will transfer energy into the crystal. Practically all we can do with a time crystal is to measure it with the lightest possible touch and hope it doesn't break the periodicity. (So far, afaik, the periodicity has always been broken by the measurement process's energy input). I don't know what we could do with large numbers of time crystals, though. One can't pick up a snowflake in one's bare hands and use it like a buzz saw to cut a sheet of paper (the snowflake melts on contact), but an avalanche of snowflakes can snap trees. Maybe for time crystals that rotate light a predictable amount at a given time t_x, we could create some sort of interesting lens from a large cloud of such time crystals arranged at different distances from a bright light source -- a sort of "anti-fog".

rpz 4y ago
If the periodicity is broken by any measurement we have been able to make so far then how do we know the periodicity is there in the first place? Just theory? If it’s not too much of a burden could you outline the proof of the existence of time crystals?
- raattgift 4y ago
  > how do we know the periodicity is there ... Just theory? Theory guides us, but experimentally you can for example make a whole bunch of time crystals (especially straightfoward for driven time crystals, which have a period that's an integer multiple of the driver, the driving force being laser light or microwaves) with an expected set of states it cycles through, and you can test those states once per time crystal. If you reliably get the states theory predicts, that's good evidence. > could you outline the proof of the existence The excellent <https://physics.aps.org/articles/v10/5 https://physics.aps.org/articles/v10/5> and decent <https://en.wikipedia.org/wiki/Time_crystal#Experiments https://en.wikipedia.org/wiki/Time_crystal#Experiments> (the former is [5] in that wikipedia article) are good starting points, with ample references.