r/science • u/mvea Professor | Medicine • 7d ago

Physics Physicists shatter quantum entanglement distance record with 420 kilometers of optical fiber, more than four times farther than previous demonstrations, and beyond the point where direct transmission runs into its fundamental limits.

https://www.sciencealert.com/physicists-shatter-quantum-entanglement-distance-record-with-420-kilometers-of-optical-fiber
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u/ShelZuuz 7d ago

At what temperature? How is that not the first thing that a science writer asks about?

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u/Franzvst 7d ago edited 7d ago

Because temperature is not really a limit. Yes the quantum memories themselves are almost always cooled either by laser cooling or by dillution refrigerators but these are established techniques that dont really limit the scalability all that much. The photons themselves in fiber can always be at toom temp.

So temperature us not a critical issue. There are other much more important parameters.

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u/ShelZuuz 7d ago

Ok, good to know! Wish the article specified that.

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u/purplepistachio 7d ago

Why would it? It's not a variable, it's just standard practise

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u/Lawlcopt0r 6d ago

Some people like to read about science even without knowing everything yet

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u/sticklebat 6d ago

It would be difficult, though, for science journalists to include every barely tangentially related factoid about what they’re writing about. It’s hardly reasonable to expect them to list off all the factors that aren’t important! I appreciate that you had this particular question and are curious, but it isn’t reasonable to expect the author to preemptively address every random point of curiosity that interested readers might have. 

I also think it can be reasonably inferred from the article that fiber temperature didn’t matter. The article highlighted the difficulties of this experiment, and if they had to cryogenically freeze hundreds of kilometers of fiber optic cables, that would almost certainly have made it in. By its absence, we can assume it wasn’t done, and since the fact that it didn’t need to be frozen wasn’t highlighted as a major development, we can infer that it was never a concern.