[HN Gopher] Two atomic clocks have been quantum entangled for th...
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       Two atomic clocks have been quantum entangled for the first time
        
       Author : lysp
       Score  : 12 points
       Date   : 2022-09-09 15:29 UTC (7 hours ago)
        
 (HTM) web link (www.newscientist.com)
 (TXT) w3m dump (www.newscientist.com)
        
       | colejohnson66 wrote:
       | From /r/science[0]: https://news.mit.edu/2020/atomic-clock-time-
       | precise-1216
       | 
       | [0]:
       | https://old.reddit.com/r/science/comments/x8khxg/two_atomic_...
        
       | rolph wrote:
       | MIT news:
       | 
       | https://news.mit.edu/2020/atomic-clock-time-precise-1216
       | 
       | seems to be the better link, also reveals subject is a 2020
       | discovery, was also published in Nature:
       | 
       | https://www.nature.com/articles/s41586-022-05088-z [paywall]
       | 
       | "Abstract
       | 
       | Optical atomic clocks are our most precise tools to measure time
       | and frequency1,2,3. Precision frequency comparisons between
       | clocks in separate locations enable one to probe the space-time
       | variation of fundamental constants4,5 and the properties of dark
       | matter6,7, to perform geodesy8,9,10 and to evaluate systematic
       | clock shifts. Measurements on independent systems are limited by
       | the standard quantum limit; measurements on entangled systems can
       | surpass the standard quantum limit to reach the ultimate
       | precision allowed by quantum theory--the Heisenberg limit.
       | Although local entangling operations have demonstrated this
       | enhancement at microscopic distances11,12,13,14,15,16,
       | comparisons between remote atomic clocks require the rapid
       | generation of high-fidelity entanglement between systems that
       | have no intrinsic interactions. Here we report the use of a
       | photonic link17,18 to entangle two 88Sr+ ions separated by a
       | macroscopic distance19 (approximately 2 m) to demonstrate an
       | elementary quantum network of entangled optical clocks. For
       | frequency comparisons between the ions, we find that entanglement
       | reduces the measurement uncertainty by nearly \\(\sqrt{2}\\), the
       | value predicted for the Heisenberg limit. Today's optical clocks
       | are typically limited by dephasing of the probe laser20; in this
       | regime, we find that entanglement yields a factor of 2 reduction
       | in the measurement uncertainty compared with conventional
       | correlation spectroscopy techniques20,21,22. We demonstrate this
       | enhancement for the measurement of a frequency shift applied to
       | one of the clocks. This two-node network could be extended to
       | additional nodes23, to other species of trapped particles or--
       | through local operations--to larger entangled systems.
       | 
       | "
        
       | kalupa wrote:
       | https://archive.ph/VVwbl
       | 
       | EDIT: ah, dang, also doesn't work
        
       | dtx1 wrote:
       | paywalled. 12ft.io doesnt help.
        
         | alexalx666 wrote:
         | 12ft is awesome, thanks!
        
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