These physicists have never properly acknowledged the prior work of Otis Eugene Ray on this subject. How typical!
Physicists have filmed the oscillation of a time crystal
21–30 of 111 posts
Re: Physicists have filmed the oscillation of a time crystal
#22How do Time Crystals differ from the quartz crystals used for time keeping in electronics? Is the only difference that Time Crystals oscillate without needing an electric field?
From my very limited knowledge of physics, time crystals can theoretically oscillate forever without any excitation at their ground state, though laws of theromodynamics are not broken and energy cannot be extracted from their oscillations. In a normal crystal oscillater, power is needed to keep the crystal oscillating.
Re: Physicists have filmed the oscillation of a time crystal
#23>filmed at up to 40 billion frames per second that's quite a feat on anyone's watch
It probably was filmed on a camera not a watch.
Re: Physicists have filmed the oscillation of a time crystal
#24>"Now, if crystals can interact not only in space but also in time, we add another dimension of possible applications. The potential for communication, radar or imaging technology is huge."
Could anyone expand on this in an accessible way? What kinds of changes could we see in imaging or communication technology?
Re: Physicists have filmed the oscillation of a time crystal
#25Since the article doesn't do a good job of explaining what a time crystal is, here's my attempt at summarizing the Wikipedia article [0].
Normally, a system which is driven by an external frequency oscillates at the same, or a multiple of the driving frequency. This is because the external conditions are symmetric under a time translation (i.e. a delay) by the period duration. This symmetry is normally preserved by the system.
A time crystal, however, will oscillate with a fraction (or rational multiple) of the driving frequency. This breaks the original time translation symmetry.
The analogy with normal 'spatial' crystals is through this symmetry breaking: Empty space is symmetric under all translations, but a crystal spontaneously breaks the symmetry group down to the smaller set of 'translations by a multiple of the lattice constant'.
The continuous symmetry of time translations cannot be spontaneously broken, due to thermodynamic arguments. Instead, we explicitly break down the time translation symmetry to 'delays by a multiple of the period duration'. A time crystal then spontaneously breaks the symmetry down even further, by multiplying the period duration / dividing the frequency.
Re: Physicists have filmed the oscillation of a time crystal
#26In the experiment, the crystals were driven by RF excitation. Do time crystals generally require a constant energy source to oscillate? I would assume not, since they're called crystals... Also, is the oscillation frequency temperature dependent?
Unfortunately, time crystals do require an external excitation. The key is that the excitation does not have the same frequency as the time crystal.
Re: Physicists have filmed the oscillation of a time crystal
#27Since the article doesn't do a good job of explaining what a time crystal is , here's my attempt at summarizing the Wikipedia article [0]. Normally, a system which is driven by an external frequency oscillates at the same, or a multiple of the driving frequency. This is because the external conditions are symmetric under a time translation (i.e. a delay) by the period duration. This symmetry is normally preserved by…
How does this compare to the behavior of nonlinear optical crystals like lithium triborate? They are also pumped at a lower frequency (e.g. 1064nm photons) but lase at twice that (532nm).
Re: Physicists have filmed the oscillation of a time crystal
#28Another scummy website that hijacks the back button. I wish there were a way to block domains from the results I see on HN.
Re: Physicists have filmed the oscillation of a time crystal
#29I wonder how this links in to optical crystals? KTP, used in solid state lasers, will halve the frequency of a IR laser (1064nm) to produce green light (532nm).
I suppose this is equivalent to adding electrical energy to a crystal to make it oscillate.
Re: Physicists have filmed the oscillation of a time crystal
#30Since the article doesn't do a good job of explaining what a time crystal is , here's my attempt at summarizing the Wikipedia article [0]. Normally, a system which is driven by an external frequency oscillates at the same, or a multiple of the driving frequency. This is because the external conditions are symmetric under a time translation (i.e. a delay) by the period duration. This symmetry is normally preserved by…
How does this compare to the behavior of nonlinear optical crystals like lithium triborate? They are also pumped at a lower frequency (e.g. 1064nm photons) but lase at twice that (532nm).
In some way, it's the inverse: a nonlinear optical system can multiply frequencies, while a time crystal divides a frequency. That's not as easy as multiplying, due to the symmetry concerns I mentioned.
It's basically a frequency divider, but as a system of cold atoms instead of an electronic circuit, and in a different frequency regime.