5 ms·

The Exquisite Precision of Time Crystals

83 points by laurex 7y ago

laserWizard 7y ago
tldr; In 1962, research for prototypical time crystals revealed when applying a constant voltage across an insulating junction separating two superconducting materials (a Josephson junction) an alternating current with a frequency proportionate to the voltage will flow across the junction. The nature of this frequency being proportional and consistent is said to be crystalline. In March of 2017, using ytterbium ions and nitrogen vacancy centers in flawed diamonds, the spin direction of atoms were manipulated to oscillate at fractional intervals within a rate of either laser pulses or microwave pulses. The pulsed inputs were operated manually by researchers, to produce the periodic intervals. END tldr; And with that, I'd like to complain about a certain type of quackery in millennial science. Specifically regarding the selection of names for principals. Here we have a certain sort of name selected for a principal, such that it elicits a sensation of WOO or hype. It's this thing, where underwhelming navel gazing seems to get dressed up in glitzy, tacky outfits, because no one would pay attention to it or fund it, if it didn't sound like a jaw-dropping breakthrough. Time crystals. So we focused beams of pulsed energy at materials, and noticed some interesting quantum effects of a given duration. We measured the duration of the effect, and then adjusted the timing of the beam pulses accordingly. Time crystals. Yeah.
blattimwind 7y ago
Timing crystals are also exquisitely precise. For example, top-of-the-line ovenized crystals achieve uncertainties of around 1 part per billion. This seems somewhat surreal for an effect that is based on mechanical resonance.
- antisemiotic 7y ago
  Time crystals mentioned in TFA are an entirelly different thing from crystal oscillators.
  - dicktwat 7y ago
    Yup, and that's why it's a stupid name.
  - ngvrnd 7y ago
    hence the "also" in the comment, one imagines.
    - antisemiotic 7y ago
      Sorry, I misunderstood then. But still, personally I think it's about as relevant as if the post was about dark matter, and someone commented "well, dark chocolate is also quite hard to detect if the fridge light goes off".
      - Accujack 7y ago
        Also technically correct.
        brylie 7y ago
        And potentially yummy, if discovered.
  - jfengel 7y ago
    Can you help me understand that? The concept of "temporal symmetry breaking" sounds exactly like oscillators. Is it that it's a quantum-scale effect, creating a truly identical system at each cycle, as opposed to the approximate classical-scale system of a conventional oscillator?
    - GistNoesis 7y ago
      If I understand the article correctly, it is a less strong constraint on the signal than being periodic, like an oscillator would be. The signal is only periodic for specific value of time, in between those value of time the signal is not periodic. To give a music analogy, the constraint is like always play the same chord on the first beat of each measure. In between you are free to play whatever chords you like. How does a physical system can acquire such property? I have no idea that's the mystery a physicist will have to explain.
- jdietrich 7y ago
  You might be interested in this documentary from 1943, which shows the manufacture of quartz timing crystals from start to finish. The amount of skilled labour required to produce a single finished crystal was utterly staggering and highlights just how essential radio communication was to the war effort. https://archive.org/details/6101_Crystals_Go_to_War_01_20_16_21 https://archive.org/details/6101_Crystals_Go_to_War_01_20_16...
  - 8bitsrule 7y ago
    Viewing the film caused me to look around for the history of the crystal oscillator (happens). Which led my to this 1948 Bell document ... ' The Evolution of the Quartz Crystal Clock' ... which starts at 1500 B.C. (They were very thorough back then.) https://web.archive.org/web/20110717061023/http://www.ieee-uffc.org/main/history.asp?file=marrison https://web.archive.org/web/20110717061023/http://www.ieee-u...
- willis936 7y ago
  Double ovenized crystal oscillators have lower phase noise (short term variations) than rubidium standard oscillators. Atomic oscillators are ridiculously cool and it's quite surprising to me that they perform worse in phase noise than a mechanical system that is thousands of times larger. The best explanation I've heard is that the signal that comes out of the physics package is a weakly modulated light source that has a (relatively) low SNR. This isn't a big deal because that signal is used to discipline a series of other oscillators. If each of those disciplined oscillators were very low phase noise you'd probably have a very nice rubidium standard, though you'd be paying many thousand dollars. https://www.youtube.com/watch?v=ymV9LwhD0W0 https://www.youtube.com/watch?v=ymV9LwhD0W0 In my last days at a test lab I examined the effect of an external reference clock on jitter noise floor measurements. It was a new BERT (1 year old) and an equivalent time oscilloscope that had not been serviced in 4 years. The external clock was a NIST TMAS rubidium standard. The measured jitter was lowest when using the instrument internal oscillators, implying the instruments have pretty excellent oscillators (no surprise) and that the effect of aging/lack of calibration had not been a serious issue. There is also the possibility that the external clock training circuits were not as nice as the internal clock training circuits.
benj111 7y ago
'Time Crystals' sounds very retro Sci fi. I'm sure Dr Who has fought a rubber masked alien or 2 over Time Crystals.
- krapp 7y ago
  There was an entire season arc where the Fourth Doctor collected the pieces of the Key to Time, which were "crystals" that assembled into a little plastic cube...
  - benj111 7y ago
    Isn't that the plot to Through the Dragons Eye[1]? Although that came 15 years later, it could just be ripping off a combination of The Chronicles of Narnia, and The Dark Crystal though. [1] https://m.youtube.com/watch?v=v9MXx9xej10 https://m.youtube.com/watch?v=v9MXx9xej10 (I remember the special effects being a lot better) Bonus points for guessing how old I am from those references.
    - krapp 7y ago
      Yeah, "collect all the pieces of the macguffin[0]" is a really common plot device, especially in anime and obviously RPGs. It's a really simple way to show "progress" without needing to bother with character development or power scaling. Bonus points if each piece of the thing has a unique power that turns out to be the cause of the conflict of the week. [0]https://tvtropes.org/pmwiki/pmwiki.php/Main/DismantledMacGuffin https://tvtropes.org/pmwiki/pmwiki.php/Main/DismantledMacGuf...
samirillian 7y ago
I like that his idea arose when he was going to teach a course on symmetry in physics. Nice reminder that teaching is absolutely useful to a person whose job it is to think.
mensetmanusman 7y ago
https://blog.mathspace.co/stones-and-apples/ https://blog.mathspace.co/stones-and-apples/ This is a useful description of space time.

83 points by laurex 7y ago

tldr; In 1962, research for prototypical time crystals revealed when applying a constant voltage across an insulating junction separating two superconducting materials (a Josephson junction) an alternating current with a frequency proportionate to the voltage will flow across the junction. The nature of this frequency being proportional and consistent is said to be crystalline. In March of 2017, using ytterbium ions and nitrogen vacancy centers in flawed diamonds, the spin direction of atoms were manipulated to oscillate at fractional intervals within a rate of either laser pulses or microwave pulses. The pulsed inputs were operated manually by researchers, to produce the periodic intervals. END tldr; And with that, I'd like to complain about a certain type of quackery in millennial science. Specifically regarding the selection of names for principals. Here we have a certain sort of name selected for a principal, such that it elicits a sensation of WOO or hype. It's this thing, where underwhelming navel gazing seems to get dressed up in glitzy, tacky outfits, because no one would pay attention to it or fund it, if it didn't sound like a jaw-dropping breakthrough. Time crystals. So we focused beams of pulsed energy at materials, and noticed some interesting quantum effects of a given duration. We measured the duration of the effect, and then adjusted the timing of the beam pulses accordingly. Time crystals. Yeah.

blattimwind 7y ago

Timing crystals are also exquisitely precise. For example, top-of-the-line ovenized crystals achieve uncertainties of around 1 part per billion. This seems somewhat surreal for an effect that is based on mechanical resonance.

antisemiotic 7y ago
Time crystals mentioned in TFA are an entirelly different thing from crystal oscillators.
- dicktwat 7y ago
  Yup, and that's why it's a stupid name.
- ngvrnd 7y ago
  hence the "also" in the comment, one imagines.
  - antisemiotic 7y ago
    Sorry, I misunderstood then. But still, personally I think it's about as relevant as if the post was about dark matter, and someone commented "well, dark chocolate is also quite hard to detect if the fridge light goes off".
    - Accujack 7y ago
      Also technically correct.
      - brylie 7y ago
        And potentially yummy, if discovered.
- jfengel 7y ago
  Can you help me understand that? The concept of "temporal symmetry breaking" sounds exactly like oscillators. Is it that it's a quantum-scale effect, creating a truly identical system at each cycle, as opposed to the approximate classical-scale system of a conventional oscillator?
  - GistNoesis 7y ago
    If I understand the article correctly, it is a less strong constraint on the signal than being periodic, like an oscillator would be. The signal is only periodic for specific value of time, in between those value of time the signal is not periodic. To give a music analogy, the constraint is like always play the same chord on the first beat of each measure. In between you are free to play whatever chords you like. How does a physical system can acquire such property? I have no idea that's the mystery a physicist will have to explain.
jdietrich 7y ago
You might be interested in this documentary from 1943, which shows the manufacture of quartz timing crystals from start to finish. The amount of skilled labour required to produce a single finished crystal was utterly staggering and highlights just how essential radio communication was to the war effort. https://archive.org/details/6101_Crystals_Go_to_War_01_20_16_21 https://archive.org/details/6101_Crystals_Go_to_War_01_20_16...
- 8bitsrule 7y ago
  Viewing the film caused me to look around for the history of the crystal oscillator (happens). Which led my to this 1948 Bell document ... ' The Evolution of the Quartz Crystal Clock' ... which starts at 1500 B.C. (They were very thorough back then.) https://web.archive.org/web/20110717061023/http://www.ieee-uffc.org/main/history.asp?file=marrison https://web.archive.org/web/20110717061023/http://www.ieee-u...
willis936 7y ago
Double ovenized crystal oscillators have lower phase noise (short term variations) than rubidium standard oscillators. Atomic oscillators are ridiculously cool and it's quite surprising to me that they perform worse in phase noise than a mechanical system that is thousands of times larger. The best explanation I've heard is that the signal that comes out of the physics package is a weakly modulated light source that has a (relatively) low SNR. This isn't a big deal because that signal is used to discipline a series of other oscillators. If each of those disciplined oscillators were very low phase noise you'd probably have a very nice rubidium standard, though you'd be paying many thousand dollars. https://www.youtube.com/watch?v=ymV9LwhD0W0 https://www.youtube.com/watch?v=ymV9LwhD0W0 In my last days at a test lab I examined the effect of an external reference clock on jitter noise floor measurements. It was a new BERT (1 year old) and an equivalent time oscilloscope that had not been serviced in 4 years. The external clock was a NIST TMAS rubidium standard. The measured jitter was lowest when using the instrument internal oscillators, implying the instruments have pretty excellent oscillators (no surprise) and that the effect of aging/lack of calibration had not been a serious issue. There is also the possibility that the external clock training circuits were not as nice as the internal clock training circuits.

benj111 7y ago

'Time Crystals' sounds very retro Sci fi. I'm sure Dr Who has fought a rubber masked alien or 2 over Time Crystals.

krapp 7y ago
There was an entire season arc where the Fourth Doctor collected the pieces of the Key to Time, which were "crystals" that assembled into a little plastic cube...
- benj111 7y ago
  Isn't that the plot to Through the Dragons Eye[1]? Although that came 15 years later, it could just be ripping off a combination of The Chronicles of Narnia, and The Dark Crystal though. [1] https://m.youtube.com/watch?v=v9MXx9xej10 https://m.youtube.com/watch?v=v9MXx9xej10 (I remember the special effects being a lot better) Bonus points for guessing how old I am from those references.
  - krapp 7y ago
    Yeah, "collect all the pieces of the macguffin[0]" is a really common plot device, especially in anime and obviously RPGs. It's a really simple way to show "progress" without needing to bother with character development or power scaling. Bonus points if each piece of the thing has a unique power that turns out to be the cause of the conflict of the week. [0]https://tvtropes.org/pmwiki/pmwiki.php/Main/DismantledMacGuffin https://tvtropes.org/pmwiki/pmwiki.php/Main/DismantledMacGuf...

samirillian 7y ago

I like that his idea arose when he was going to teach a course on symmetry in physics. Nice reminder that teaching is absolutely useful to a person whose job it is to think.

mensetmanusman 7y ago

https://blog.mathspace.co/stones-and-apples/ https://blog.mathspace.co/stones-and-apples/ This is a useful description of space time.