this post was submitted on 28 Aug 2024
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Science Memes

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Don't look now (lemmy.zip)
submitted 2 months ago by [email protected] to c/[email protected]
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[–] [email protected] 2 points 2 months ago (4 children)

could a record like this be used as a presence detector? Like if there was any observer who collapsed the wave function then we’d get the collapsed lines in the log, otherwise it would have indicated no observers? (obviously even what the hell is an ‘observer’ anyway?)

[–] [email protected] 2 points 2 months ago (1 children)

Yes. This is how motion detectors work. Normally, motion detectors have an IR emitter that acts as a particle, but when someone walks by, the IR emitter works as a wave, triggering the motion detector.

Notably, this doesn't work with dogs, as they have no souls.

[–] [email protected] 1 points 2 months ago (1 children)

Notably, this doesn't work with dogs, as they have no souls.

Which kind of motion detectors? The ones I know work on everything that's moving, including my cats (don't have dogs) or even just throwing something past it

[–] [email protected] 3 points 2 months ago

Oh, you might have one of the newer ones that use interferometry to detect soulless entities.

[–] [email protected] 4 points 2 months ago

Observer here doesn't mean the same as the layman meaning. It's anything that interacts with the system while it's developing.

Interestingly, it actually can be used for a presence detector, at least in a sense. You can use it to transfer cryptographic information. If no-one is listening in, about half your sent numbers are wrong, but you can agree on what ones. However, if someone is listening in, all your data gets randomised.

They actually now use this system to transfer information between banks. They send a random stream of 0s and 1s over a fibre optic cable. They then send (semi publicly) which bits made it properly. If someone spliced into the fibre, they would get the encryption data, but the target bank would not! They know instantly that something is wrong.

[–] [email protected] 2 points 2 months ago

Yes. Trust me, am science guy.

[–] [email protected] 9 points 2 months ago (1 children)

A log is an observance itself. Any measurement changes the state.

[–] [email protected] 4 points 2 months ago (4 children)

How is the unobserved state ever known about, then?

[–] [email protected] 1 points 2 months ago (1 children)

We can observe the end result. E.g. observing the screen only, and you get wavelike behaviour. When you also observe the slit, the wavelike behaviour disappears, and it seems particle like.

Both end in an observation, 1 has an extra observation.

[–] [email protected] 1 points 2 months ago (1 children)

yeah so if I looked at a log of all that, wouldn’t I have a “extra observer” detector, then?

[–] [email protected] 2 points 2 months ago

You could detect decoherence in the system, that doesn't indicate a human observer, however.

That process is, however, used to protect cryptographic keys, transfered between banks. A hostile observer collapses the state early. The observer gets the key instead of the 2nd bank, which is extremely conspicuous to both banks.

[–] [email protected] 0 points 2 months ago

It is "guessed" using whatever mathematical model that matches the system.

Of course, if our whole theory is wrong, then the guess will be wrong and we won't know unless some condition arises where the predicted result and the observed result are different.

[–] [email protected] 5 points 2 months ago

You observe the result, not the experiment while it is running.

[–] [email protected] 4 points 2 months ago

They say, “I’m not peeking” but cross their fingers behind their back.