Comment on Electrons

• i_love_FFT@lemmy.ml ⁨5⁩ ⁨weeks⁩ ago

  It’s either up or down whatever the direction.

  If you measure 100%up-0%down then you rotate your frame of reference by 90°, you automatically get 50%up-50%down… (iirc)

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  • Ziglin@lemmy.world ⁨5⁩ ⁨weeks⁩ ago

    Just in case it wasn’t clear you can’t measure anything other than “100%” up or down spin. The quantum state of it being 50/50 is described by 1/sqrt{2} times the up and down vector, when you measure it you have a probability of getting either result calculated by the square of the absolute (||psi||^2) that way you avoid getting a complex probability.

    btw I was too scared to try in case it doesn’t but can I use LaTeX in Lemmy comments? $\psi$

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    • i_love_FFT@lemmy.ml ⁨5⁩ ⁨weeks⁩ ago

      True! Thanks for the clarification, it’s been a while since i played with the maths of quantum physics!

      After you measure a spin as 100% up, the state will be close to that for a while, si the next measurement has higher chance of being up, with this probability slowly decreasing with time.

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      • Ziglin@lemmy.world ⁨5⁩ ⁨weeks⁩ ago

        I think that assuming the particle has no (extra?) energy it’s state does stay the same. That is of course not possible in real life though but the <20 millikelvin in some quantum computers get pretty close.

        Also I think nobody says they measure it as 0/100% up, They just say up or down in my limited experience.

        Does anyone have any good resources on quantum mechanics? (Most of my information comes from a few professors) There’s some useful stuff on chem libretexts (I think that’s what it’s called) for simple wave functions, but it doesn’t seem perfect.

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• Ziglin@lemmy.world ⁨5⁩ ⁨weeks⁩ ago

  At least in the Stern-Gerlach experiment it’s relative to the magnetic field.

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  • Chrobin@discuss.tchncs.de ⁨5⁩ ⁨weeks⁩ ago

    Yeah, quantum mechanics lingo: measurement = interaction

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