Observer Effect

>>9102651
I guess you can think about it loosely in terms of entanglement. 'Free' particles have limited entanglement and so exhibit wavelike properties. The probabilistic pattern occurs through slits when particles are not sufficiently entangled with other matter. When they do become sufficiently entangled (aka observed), the probabilistic pattern ceases. In essence, everything about macroscopic matter is highly entangled and it's why weird quantum effects don't manifest themselves outside of very specific situations.

>>9102673
I'm not quite sure what you mean by entanglement (and entangled enough) here. I thought entanglement was only between particles? Doesn't observation cause decoherence?

To observe is to interact.(((period)))

>>9102821
Yeah, so would prohibit entanglement

Not op, but can someone explain this to me assuming a normie amount of knowledge in entanglement?

>>9103262
OP here. Afaik, entanglement is when a system has one or more particles 'linked' to another. By linked I mean that you cannot treat them individually/independently so have to look at the wavefuncion of the systems as a whole (Wfcns are a way of describing how a QM system/particle evolves)

>>9103374
If you know Dirac notation then if you were looking at spin say of 2 entangled photons you could not treat them independently but you'd have to use the wavefcn of the whole system which is a sum over possible states of the two photons i.e.

[eqn]|\Psi_{sys}> \space= \sum_{states} |A>|B> \space= |\uparrow_{A}>|\uparrow_{B}> +|\downarrow_{A}>|\downarrow_{B}>[/eqn]

(I may have gotten the spins wrong, it might be up paried with down for A & B I cant remember.)

NB If anyone knows how to do non-gross bra-ket notation on /sci/ let me know, you don't seem to be able to import the physics package I'm used to.

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>>9103395
No idea why that eqn didnt work so here's it from the preview pane

>>9103401

use \langle and \rangle

moreover I what do you mean by the product of a ket with another ket?

When you fuck up the plating on the dish you were going to give to your gf, but do the rest of plates just fine it may appear that a strange force is acting against you and everything you love. But in reality it is because you cared, you wanted it to be perfect that then overcomplicated the plating, did 1001 forced little tweaks that ended fucking up everything; when acting normally was just fine.

So, you try to give the experiment optimal conditions at the moment, you interact with its surroundings and end up interacting with the object

TL:DR >>9102821

>>9103433
Tyvm. Ah yeah I omitted my tensor products, sorry for the confusion.

>>9103675
I get that interactions == observations. I guess a clearer way of formulating my question is given the non-locality of a particle's wavefunction how can we deem it to only interact with one 'thing' at a time.

>>9103675
Wait.

Can you explain that again in some other way? How can I (observer) change what happens just because I looked at it? And what does it mean looking at it? A photograph can be an observation indirectly.

>>9103708
Liken it to taking a photograph in the dark. You can't do it without shining a light on the object. This light allows you to make an observation, but fundamentally interacts (and so changes) the object.

>>9103708
Two ways
You either use something to make your observations >>9103734
Or how I said, you may not try to make observations at the moment, but your very presence makes it very likely for you to make changes, either moving the flask to a "better place" white it reacts; or trying to control at the very moment some variables thinking that you are making it more "natural" when in actuality you are affecting the subject

>>9103828
I forgot
If you want to get very anal about it then the simple act of knowing changes the subject, or at least our perception of that object

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>>9102651

>Not doing path integrals in high school

Point and laugh

>>9103734
In that case light changes the particles and since light is energy that energy causes the particles to change.

We are bound to observation through our 5 senses and everything that we need to reflect on the particles to make observation will modify the particles state.

So what can we do to make observation without shining something on what can be changed by it? I always think of the example that something only truly exist if its causality and non-observation can actually kill you. So you can die of something that you never experienced/observed. It actually becomes confusing in a way that you don't know how you were born either like a dream where you don't remember how you got there. But you are sure you were born since you know you are existing at this moment.

>>9103837
I've done calculus of variations plenty of times. Feynman path integrals did not come up in any of my QM courses. We used operator notation for this sort of stuff.

If you can't tell the difference between path integrals and actual action-angle calculations dealing with locally restricted (on shell) QFTs then maybe you need to go back to education

>>9103837
FPIs require complex analysis - not done in high school