[HN Gopher] For precision, the sapphire clock outshines even the...
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       For precision, the sapphire clock outshines even the best atomic
       clocks
        
       Author : ystad
       Score  : 46 points
       Date   : 2021-08-19 11:43 UTC (1 days ago)
        
 (HTM) web link (spectrum.ieee.org)
 (TXT) w3m dump (spectrum.ieee.org)
        
       | jjoonathan wrote:
       | Hah, the editor must have banned the term "phase noise"!
       | 
       | Impressive accomplishment.
        
         | a9h74j wrote:
         | No way to infer a Q, either.
        
         | spot5010 wrote:
         | Indeed. No mention of Allan deviation, and no links to
         | references. I found this old reference
         | 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 for 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.
        
       | PoignardAzur wrote:
       | The headline is the perfect blend of sci-fi and fantasy.
        
       | mbertschler wrote:
       | > But for some applications, accuracy is less important than
       | precision. Precision has to do not with delineating the perfect
       | second but rather with creating extremely regular ticks, or
       | oscillations.
       | 
       | I don't follow here, doesn't accuracy follow if you have a
       | precise oscillator? What is the difference between an accurate or
       | a precise clock?
        
         | nightfly wrote:
         | It implies that the "tick" intervals in atomic clocks aren't
         | always the same length in time, they just average out very
         | well. While the new sapphire clocks have a more consistent tick
         | interval.
        
           | tehbeard wrote:
           | So.... Cesium clock is "guaranteed" 10 ticks in X timespan,
           | but the distribution is not perfectly equidistant? Do I
           | understand that correct?
        
       | ticktockkasdf wrote:
       | The distinction between precision and accuracy in the article
       | leaves a lot to be desired. Couldn't we just redefine the second
       | to be X number of ticks of this clock?
        
         | rtkwe wrote:
         | There could be issues with creating accurate copies of this.
         | You could still get very precisely spaced ticks but not get an
         | accurate measure that could be replicated around the world. A
         | standard doesn't work well if there's one extant copy you can
         | compare against. That's why they're working so hard to create a
         | new standard kilogram where it could in theory be replicated
         | without reference to the original.
        
         | totallyabstract wrote:
         | Presumably two different instances of this clock would have
         | different tick rates due to the specific crystal used and it's
         | very difficult to produce two identical crystals.
         | 
         | An atomic clock is very consistent across devices as it
         | exploits the properties of an element which is much more
         | repeatable (just have to have a quantity of the element).
        
       | fjfaase wrote:
       | I wonder if this could also be used to more accurately time
       | pulsar signals and be used to detect gravitational waves?
        
         | Anon854 wrote:
         | Yes, it can. Andre's PhD was using this on a bar detector.
        
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