Don't look now
Don't look now
26 comments
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For those confused, it's worth noting the difference between observed as a layman concept and as a quantum mechanical one.
In QM, to observed is to couple the observer to the "system" being observed. Think of it like "observing" your neighbour, over a fence using a BB gun. When you hit flesh, you know where your neighbour is. Unfortunately, the system has now been fundamentally changed. In a classical system, you could turn down the power, until your neighbour doesn't notice the hits. Unfortunately, QM imposes fundamental limits on your measurements (heisenburg and his uncertainty principal). In order to observe your neighbour accurately, you need to hit them hard enough that the will also feel it and react differently.
QM behaves in a similar way. Initially, the system is just a single particle, and is not very restrained. This allows it to behave in a very wave like manner. When you observe it, the system now includes the whole observation system, as this coupling propagates, more and more atoms etc get linked. The various restraints cause an effect called decoherence. The system behaves ever more like a classical physical system.
In short, a quantum mechanical "observer" is less sneaky watching, and more hosing down with a machine gun and watching the ricochets.
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Thanks! I’ve never fully grasped the concept and this really helps.
I’ve always heard it that observing was actually “measuring” and still wasn’t sure why that would impact anything but chalked it up to the quantum world being other-worldly.
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Honestly physicists don't actually know what measuring is either. We don't know when exactly the system is considered "measured" in the chain of entanglement, this is called the Measurement Problem.
Answers range from "shut up don't think about it" to "there's an infinite amount of universes split from each other for each quantum event!".
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To be honest I still chalk it up to that.
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Thank you for the explanation! Almost got into an argument a while back because someone was conflating the layman definition with the QM definition as proof of some kinda metaphysical effect of the human consciousness.
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Sure, but that still means the photons derender when nobody is watching them
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“Greg, we got an order for a lot of unobserved results. Take the rest of the week off.”
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in a nutshell: punch particles in the face, get surprised they behave differently
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I observe what you did there.
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2060 job posting, Quantum Stability Engineer.
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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?)
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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.
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Yes. Trust me, am science guy.
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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.
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26 comments