3 ms·

Hah, the editor must have banned the term "phase noise"! Impressive accomplishment.

a9h74j 5y ago
No way to infer a Q, either.
spot5010 5y ago
Indeed. No mention of Allan deviation, and no links to references. I found this old reference https://ieeexplore.ieee.org/abstract/document/918181/ https://ieeexplore.ieee.org/abstract/document/918181/ Which claims a short term Allan deviation of 5.4e-16/sqrt(tau) for 1-4s. This is pretty impressive and is comparable to Rb or Cs clocks for short time scales. The best optical clocks achieve something like 1e-18/sqrt(tau). Of course, since the sapphire oscillator is not locked to an absolute reference they drift after a few tens of seconds.
- jjoonathan 5y ago
  Yeah, let's throw some dBc/Hz @ 10kHz offset too for good measure, just to confound the editor :} Aren't stability units grand? Hey, I'm just glad we heard from them before they got body snatched. (Context: since you can drop a low-phase-noise clock into a radar and improve the performance, this area of research is one that the spooky defense types pay active attention to. Many physics departments have legends about projects like this suddenly vanishing into classified status.)
  - spot5010 5y ago
    Interesting. I’m guessing for radar applications it’s really the phase noise above a certain frequency that matters.
nextaccountic 5y ago
What do you mean?
- segfaultbuserr 5y ago
  The article used simplified explanations and analogies, such as > Tick, tick, tick. The rhythm of clocks is universal. But how exactly alike are those ticks? > [...] Precision has to do not with delineating the perfect second but rather with creating extremely regular ticks, or oscillations. Imagine a game of darts. Atomic clocks are able to land all their darts, or oscillations, broadly around the bull's-eye so that the average position is right on target, even though any given dart might be a centimeter or two away from dead center. Luiten's device doesn't aim for the bull's-eye: instead, it is able to land all its darts at exactly the same point on the dartboard. In other words, each tick is really, really, really just like another. But didn't even once mention the technical term for that in the entire article, making it more difficult to see what the author is talking about for people with an engineering background. This is simply known as jitter, or phase noise. It's especially funny given that the IEEE Spectrum's audience is engineering-minded readers.
  - nextaccountic 5y ago
    Ok thank you! Jitter is a term I'm familiar with, but I've never heard phase noise before (but it makes sense)

No way to infer a Q, either.

Indeed. No mention of Allan deviation, and no links to references. I found this old reference https://ieeexplore.ieee.org/abstract/document/918181/ https://ieeexplore.ieee.org/abstract/document/918181/ Which claims a short term Allan deviation of 5.4e-16/sqrt(tau) for 1-4s. This is pretty impressive and is comparable to Rb or Cs clocks for short time scales. The best optical clocks achieve something like 1e-18/sqrt(tau). Of course, since the sapphire oscillator is not locked to an absolute reference they drift after a few tens of seconds.

jjoonathan 5y ago
Yeah, let's throw some dBc/Hz @ 10kHz offset too for good measure, just to confound the editor :} Aren't stability units grand? Hey, I'm just glad we heard from them before they got body snatched. (Context: since you can drop a low-phase-noise clock into a radar and improve the performance, this area of research is one that the spooky defense types pay active attention to. Many physics departments have legends about projects like this suddenly vanishing into classified status.)
- spot5010 5y ago
  Interesting. I’m guessing for radar applications it’s really the phase noise above a certain frequency that matters.

nextaccountic 5y ago

What do you mean?

segfaultbuserr 5y ago
The article used simplified explanations and analogies, such as > Tick, tick, tick. The rhythm of clocks is universal. But how exactly alike are those ticks? > [...] Precision has to do not with delineating the perfect second but rather with creating extremely regular ticks, or oscillations. Imagine a game of darts. Atomic clocks are able to land all their darts, or oscillations, broadly around the bull's-eye so that the average position is right on target, even though any given dart might be a centimeter or two away from dead center. Luiten's device doesn't aim for the bull's-eye: instead, it is able to land all its darts at exactly the same point on the dartboard. In other words, each tick is really, really, really just like another. But didn't even once mention the technical term for that in the entire article, making it more difficult to see what the author is talking about for people with an engineering background. This is simply known as jitter, or phase noise. It's especially funny given that the IEEE Spectrum's audience is engineering-minded readers.
- nextaccountic 5y ago
  Ok thank you! Jitter is a term I'm familiar with, but I've never heard phase noise before (but it makes sense)