Doesn't Schrodingers cat make it plausible that some humans are walking around with their own wave functions...

No. Wave functions "collapse" on their own through any interaction with the environment; it's why quantum computers are so hard to build. The process is known as decoherence, and big warm messy objects like humans and cats which are constantly emitting and absorbing photons and interacting with zillions of air molecules decohere basically instantly.

According to some interpretations of quantum mechanics, all apparent wavefunction collapse due to "observation" is just decoherence, because measuring instruments and humans are big and decohere rapidly.

Decoherence is not the same as collapse, you morons.

This is called the "measurement problem" of quantum mechanics.
plato.stanford.edu/entries/qt-measurement/

No. See:
plato.stanford.edu/entries/qm-decoherence/
> Thus, decoherence as such does not provide a solution to the measurement problem,

I was specifically referring to the Many-Worlds interpretation, where there really is only decoherence and no collapse; if you observe a quantum superposition, the state of your brain/mind becomes entangled with its state, you decohere, and the result is two non-interfering, essentially wholly independed and classical-seeming states, one in which you observed each eigenvalue. From within, this appears exactly identical to the state "collapsing" to a single randomly-picked eigenvalue with the rest of the superposition vanishing. You are now, in effect, observing the superposition from the *inside*.

Consistent-histories and "Quantum Bayesian" frameworks are similar; if Many-Worlds is the natural extension of the Schrodinger wave-mechanics formulation of QM, Consistent Histories is a similar extension of the Feynmann path-integral formulation.

> Thus, decoherence as such does not provide a solution to the measurement problem,
You forgot the next bit:
>...at least not unless it is combined with an appropriate interpretation of the theory (whether this be one that attempts to solve the measurement problem, such as Bohm, Everett or GRW

That is why I deliberately specified
>According to some interpretations of quantum mechanics

Because yes, decoherence on its own with no framework for interpretation does not address the measurement problem. Within some frameworks for interpetation, however, it does.

>I don't know what Schrodingers cat is
>I don't know even basic high school chemistry/physics
Schrodingers cat was made to show how stupid quantum mechanics would be on the large scale and why it doesn't work.
It was made sarcastically.

I did learn something new from the link, and you. Thanks.

you obviously don't want a real answer, but I'm curious as to how large a system can be while maintaining an uncollapsed wave function. and if it can be large does that correspond to a smaller difference in possible outcomes

...

Schrodinger's cat was never intended to be a tool or metaphor for understanding the implications of observation in a quantum system.

nor was it "sarcastic"... more like a genuine and serious challenge (those guys did not speak to each other as if on 4 chan)

Personally, i think the cat would count as an observer and never be in a dual dead/ alive state..
Someone should also point out that the superimposition of quantum states is a firm, not even really debatable, aspect of QM that has been experimentally demonstrated. It is not a "fringe" or "hotly debated" part of QM. Superimposition is probably the biggest thing that makes solving quantum equations different than solving classical equations. Its in the math itself, and it allows us to predict quantum phenomena with great accuracy (accounting of course, for the fact that these predictions are probabilistic) - and if your about to shit on the probabilistic part.... remember that the probabilities people love to hate on here at Veeky Forums can and do work out to 100% in certain situations

it mostly comes back to a particle taking all possible paths until "measured". that bit implies most of the rest in entanglement superposition and wave collapse if you're interested in connecting everything and having an intuitive understanding

yes, and the possible paths interfere with each other in "potentia" , and the results are consistent and measurable in real experiments. This is the point that never seems to get through here on Veeky Forums and it kind of drives me mad. Its established physics. Thanks for being on the reasonable team

Explaining the measurement problem can be hard. Using that name, and linking to an article about it, is suggested.

Well, the impulse of a human is too big to get altered by a photon. De Boglie: Wavelength = h/p.

is the measurement problem not just an interaction problem?

Can you explain how it is an actual problem?

In short:
Imagine a situation where we create a particle that is a 50-50 superposition of two states. Imagine we have a device in the lab that measures the state of that particle, with a pointer that points to the left for one state, and points to the right for the other state.

In common quantum mechanics talk, it is said that this measuring device performs and observation, collapses the wave function, and we get one definite result. We see the macroscopic pointer either pointing to the left or pointing to the right.

However, the lab device itself is composed of quantum particles that themselves obey quantum mechanics. If we simply and naively apply Schrodinger's wave equation to the situation, we find that the particles that make up the measuring device also enter a quantum superposition of states. The pointer is in a 50-50 superposition of states, one state where the pointer is pointing to the left, and one state where the pointer is pointing to the right. Obviously, we never see that, so we want to solve this problem.

Again, the conventional solution that everyone uses now is the following:

Step 1: Apply the Schrodinger wave equation.

Step 2: At ill-defined points in the mathematical process, collapse the wave function.

This has been true for the whole history of quantum mechanics. Go back to the earliest writings, and you will see this "2 step" or "2 action" process, and you will also see all of the greats of quantum mechanics complaining about this horrible state of affairs.

The process works. We get incredibly accurate results that match experimental data. However, the process is also incomplete and ill-defined. There is no proper rule that tells us when to stop the time evolution according to Schrodinger's wave equation, and collapse the wave function. In other words, there is no proper definition of what constitutes a "measurement" or "observation" for the purpose of collapsing the wave function.

So, the problem is: We never see our macroscopic measuring devices in a superposition of states, but if one would apply the math straightforwardly, it tells us that our macroscopic measuring device will end up in a superposition of states. Ergo, at the beginning of quantum mechanics, they invented the second rule "when a macroscopic observation happens, the wave function collapses".

The question then becomes: Is that "real"? Does the wave function really collapse? When does it collapse? Under what circumstances, exactly?

Common solutions to this problem are the following:

The Everett interpretation, aka the many-worlds interpretation, plus decoherence. I'm probably going to butcher this, but in short, every quantum possibility happens in parallel, the wave function of the universe never collapses, and our conscious first-person awareness picks one of the classical paths at random. With decoherence, almost all of the paths follow a path where the macroscopic measuring device is not in a superposition, and we always see a well defined result of "pointing left" or "pointing right".

Bohmian mechanics. You can create a deterministic description of quantum mechanics, but you have to give up locality. The math of this approach is not as well developed as the standard quantum theory math. It's defined to give equivalent predictive results.

to be continued

Spontaneous collapse models. The general idea is that superpositions never happen for macroscopic objects, because every quantum particle will randomly provoke a collapse of any superposition that it is part of at random intervals, similar to spontaneous nuclear radioactive decay. The math is not as well developed as the math of the standard quantum mechanics interpretation. Finally, this option has the added benefit that it's not just another "interpretation" of quantum mechanics. It makes different predictions, which means it's actually a different theory, and we can actually test if it's right or wrong. It makes almost the same predictions as quantum mechanics, but it differs slightly. To test the differences is very, very hard, so hard that it hasn't been done yet, but it is in principle testable, and it might be tested in our lifetimes.

This post prolapsed my ass function

How quantum systems measurements are taken? What device used? This is more mystery than Schrodinger cat

Your post collapsed my cancer's wave function :(

The detector is the observer. This kills the wave.

lmao dude 420 weed

This comic is stupid and based on another pop sci misinterpretation. Schrödinger's cat wasn't invented with the intent of criticizing the Copenhagen interpetation.

"Schrödinger did not wish to promote the idea of dead-and-alive cats as a serious possibility; on the contrary, he intended the example to illustrate the absurdity of the existing view of quantum mechanics.[1]"

1. Schrödinger, Erwin (November 1935). "Die gegenwärtige Situation in der Quantenmechanik (The present situation in quantum mechanics)". Naturwissenschaften 23 (48): 807–812. Bibcode:1935NW.....23..807S. doi:10.1007/BF01491891.

No, that's the opposite of the case.
Schrödinger didn't like how quantum mechanics worked, because it predicts that a cat can be dead and alive at the same time (more specifically in a superposition of alive and dead). That is something that quantum mechanics does actually predict, and he constructed the example to show how ridiculous quantum mechanics is.
Of course, it is now understood that he had nothing to be worried about, and his cat experiment should probably not be mentioned any more.

Quantum mechanics is a meme.

I read the original paper, you fucking retard. You should do so as well. Because the cat was not about the Copenhagen interpretation. On the contrary he addressed a misunderstanding of said interpretation.

>Schrödinger didn't like how quantum mechanics worked, because it predicts that a cat can be dead and alive at the same time
Oh look, another retard who didn't read Schrödinger's original paper.

I FUCKING LOVE SCIENCE

I'm just a stupid ass law student but what the fuck is the truth about the Schrödinger's cat then? Was it an example, joke, criticism or something else?

>I was specifically referring to the Many-Worlds interpretation, where there really is only decoherence and no collapse; if you observe a quantum superposition, the state of your brain/mind becomes entangled with its state, you decohere, and the result is two non-interfering, essentially wholly independed and classical-seeming states, one in which you observed each eigenvalue. From within, this appears exactly identical to the state "collapsing" to a single randomly-picked eigenvalue with the rest of the superposition vanishing. You are now, in effect, observing the superposition from the *inside*.
But to actually explain decoherence you need to have some description of measurement. Decoherence is an approximation to this fundamental measurement, which one still needs to postulate in many-worlds in the form of "splitting" the universe, or collapse in Copenhagen. This is why many-worlds isn't really more intuitive or philosophically pleasant than any other interpretation, and the approximation of decoherence cannot side-step the fact that quantum mechanics is not a realist theory.

I should point out that it is very much incorrect to say that interaction causes collapse (be that with the environment or otherwise, the distinction between the two being a subjective choice); collapse is caused by measurement. Measurement is whatever causes you to update your information about the system. Particles interact with each other all the time with nothing collapsing, and you can cause collapse without any interaction taking place.
Take the double slit experiment: if you place a detector in front of one slit, the interference pattern disappears completely. If the detector is on the left slit and the electron goes through the right you still see no interference, because the detector not going off still allows you to update your information about which way it went. If interaction caused collapse, you'd only collapse the wavefunction when it went through the detector.

particles spin spin spins spin spin pspin spins pin spin spin spinspsjnpsns psjn

It was meant to highlight a certain misunderstanding people at that time used to have about the Copenhagen interpretation.

He calls the situation ridiculous, and says that the definition of measurement is not without its faults, which he then outlines.

No he doesn't. He says that this presents a problem for "a 'blurred model' for representing reality, i.e. the Copenhagen interpretation. His claim is that if we accept the Copenhagen interpretation on the atomic scale we must also accept it when it leaks into the macroscopic world, which is problematic.

tuhh.de/rzt/rzt/it/QM/cat.html#sect5

>He calls the situation ridiculous
Of course he does, you fucking retard, because he wants to highlight a misunderstanding. He does not criticize the Copenhagen interpretation, which at this point he - as one of its founding fathers - still supports.

>"a 'blurred model' for representing reality, i.e. the Copenhagen interpretation
You don't know shit about QM, I see.

Give me link to the practical aspect of quantum mechanics. How measuruments are actually taken?

>You don't know shit about QM, I see.
Considering you have not backed up your claims with a single piece of reasoning, I think you're projecting. It's clear that Schrodinger is talking about the Copenhagen interpretation which was the new standard at the time he wrote this article. But feel free to actually give an argument about what he was *really* talking about, and go ahead and correct wikipedia while you're at it.

Schrödinger was one of the creators of the Copenhagen interpretation. He was the main force behind the wavefunction formalism. His point with the cat was that at no point the actual cat is in superposition. The Copenhagen interpretation does not state that things are "blurred" or "smeared", it only gives a mathematical formalism for computing probabilities of measurement outcomes. This is exactly the misunderstanding Schrödinger wanted to address with his cat thought experiment. Now please go back to your retarded pop sci youtube channels for children, you braindamaged cretin.

THANK YOU.

>Schrödinger was one of the creators of the Copenhagen interpretation. He was the main force behind the wavefunction formalism.
Now I am fairly certain YOU don't know what you're talking about. There are many ways to interpret what the wavefunction means, and the Copenhagen interpretation is just one of them. Schrodinger was only a "founder" insofar as his work serves as a jumping off point for Heisenberg and Bohr, who were the true proponents of the Copenhagen interpretation. So your argument rests on a factually incorrect assumption, that Schrodinger was a proponent of the Copenhagen interpretation simply because some of his ideas were used in it.

>His point with the cat was that at no point the actual cat is in superposition.
Yes, that's the absurdity of the thought experiment. If we take the Copenhagen interpretation as true, that the atomic system does not have definite properties until it is measured, then this implies that what it determines does not also have definite properties until it is measured, i.e. the cat is neither alive nor dead (or in his words, both alive and dead). Schrodinger's point is that it is absurd to think this way, that macroscopic objects should have definite properties even before measured.

So far you have failed to give a reason why we should assume this is not a criticism of the Copenhagen interpretation. If you can't formulate a coherent argument, you should be able to find some physicist who can. Surely, since I am allegedly completely ignorant of QM and you are not, there should be many experts who agree with you?

Thanks.

You seem to be confusing the Copenhagen interpretation with QM in general. The wavefunction is simply a mechanism (as you said, it's a mathematical formalism). The Copenhagen interpretation is an *interpretation* of what those formalisms "physically mean".

I'm sorry to hear that you have only a pop sci understanding of the Copenhagen interpretation. The CI does not make any statement about the ontological status of the wavefunction prior to collapse. And this was the point of Schrödinger's cat. To demonstrate the absurdity of mistaking the CI for "hurr durr the physical object is smeared/blurred". What he criticized was not CI but a common misunderstanding of CI. Your lack of literacy is worrisome.

>The CI does not make any statement about the ontological status of the wavefunction prior to collapse.
Where did I say it does? What I said: "If we take the Copenhagen interpretation as true, that the atomic system does not have definite properties until it is measured"

Instead of agreeing or disagreeing, you attacked a strawman argument.

>To demonstrate the absurdity of mistaking the CI for "hurr durr the physical object is smeared/blurred"
He is stating that this is what the CI implies. I cannot find a single reputable source who thinks that Schrodinger was promoting the CI in this article. Your opinion is unsubstantiated and fringe.

en.wikipedia.org/wiki/Quantum_decoherence

Decoherence is derived from the math of quantum mechanics itself; it's not a philosophical concept, and it's not a property of Many-Worlds; decoherence is an observed phenomenon which objectively, experimentally happens in all interpretations, and Many-Worlds just takes the position that it can explain all observations of "collapse". To give a very loose description, as the environment interacts with a quantum superposition, the entire environment becomes entangled with that quantum state (Popsci: the "quantumness" "leaks out" from the small isolated system into a much larger system with a lot more degrees of freedom, "diluting" it), and the two states (mostly) stop interfering with each other. That is what is meant by Many-Worlds "splitting" the universe - the wavefunction of the system and environment considered as a whole never collapses, but the entire world is now in a sort of superposition, and the component states of that superposition no longer interfere with each other.

This is why it's not correct that decoherence is caused by interaction in general, and it's not an all-or-nothing process like "collapse". You can read a better description on the page than I could explain well here.

The reason people say this could explain the measurement problem is that humans - and human brains, and thus human minds - are part of the environment, and the very concept of a "measuring device" could basically be rephrased as "a device for entangling the state of a human mind with that of a quantum system". And this whole process, whereby interacting with a superposition in a way that entangle it with a large macroscopic system that happens to house our mind causes it to appear to suddenly turn into a single isolated component state with the rest of the superposition suddenly vanishing, seems to look a whole lot like what we'd expect decoherence to look like from the inside.

>He is stating that this is what the CI implies.
But that's wrong, you retard. He does not mention CI at all in his paper.

And, just for balance, here's some serious problems of interpretation that Many-Worlds does not solve:

>The basis problem

>Why the Born probabilities?

These are both pretty big problems, and are why while Many-Worlds has some very nice features it's very far from universally accepted.

Side-stepping your argument here, I would point out that Schrödinger ultimately became dissatisfied with Copenhagen. Whether he was indirectly criticising it, did not intend to criticise it, or changed his mind later is a biographical matter that we'll probably never know the answer to.

So an article titles "The Present Situation in Quantum Mechanics" does not mention with what was then the newly minted standard interpretation of QM?

And he is criticizing a certain view of the Copenhagen interpretation, but does not mention the Copenhagen interpretation? Your argument is absurd. Find a source for your ridiculous claims or fuck off.

>I would point out that Schrödinger ultimately became dissatisfied with Copenhagen
Yes, this is well-known but has nothing to do with the cat.

Just read the fucking paper and stop being stupid.

>another thread where people invoke QM in their stupid philosophy
This stuff sounds like Biblical fundamentalism

>Just read the fucking paper and stop being stupid.
I read the paper already. You have no argument. You lose.

Then show me where it mentions Copenhagen. Protip: The word doesn't appear even once.

The term "Copenhagen interpretation" was not used to describe it until the 50s, you absolute moron.

Good, we're gettting closer to educating you dumbass. Now please show me where and how he describes what you believe to be the Copenhagen interpretation.

you sound like an absolute smug retard to be honest. i don't know why the fuck the user is bothering to please your idiotic ass

So we've gone from

>Schrodinger was defending the CI

to

>Schrodinger never mentioned the CI

to

>Schrodinger never mentioned the word "Copenhagen"

But I'm the one who didn't read the article...

Start reading at "4. Can One Base the Theory on Ideal Ensembles?" where he explains what he means by "blurred reality" (which is a colloquial)

These three are not mutually exclusive. You are grasping at straws because you fail to substantiate your claim. There is no evidence that the paper aimed to criticize Copenhagen interpretation. Said interpretation is neither directly nor indirectly mentioned. Schrödinger explicitly explains which misconception he aims to address with the cat analogy, and this misconception is not the CI.

And?

Veeky Forums - Science & Math

Philosophy isn't a real science.

>Decoherence is derived from the math of quantum mechanics itself; it's not a philosophical concept, and it's not a property of Many-Worlds; decoherence is an observed phenomenon which objectively, experimentally happens in all interpretations, and Many-Worlds just takes the position that it can explain all observations of "collapse".
That's exactly what I was saying.

>These three are not mutually exclusive.
They are mutually exclusive in this context. The first is unlikely given the second, and once one reads the article and sees that Schrodinger is thoroughly discussing the development of QM up to the present, it becomes absurd to hold both at the same time. And then both become false when you read sections 4 and 5. The third is simply a non-sequitur.

>You are grasping at straws because you fail to substantiate your claim.
You are projecting.

Once you read this you understand that the context of Schrodinger's discussion is the EPR paradox, which is another criticism of the CI. The "blurred reality" is clearly a reference to the superposition. Schrodinger's intent was clearly to criticize the concept of the superposition by showing it could be extrapolated to macroscopic phenomenon. Every source discussing Schrodinger's cat describes this. Provide a source for your claims or fuck off.

>They are mutually exclusive in this context.
Are you trolling?

>The "blurred reality" is clearly a reference to the superposition
Holy fuck, you can't be serious. Throughout the thread I explained to you why this is wrong.

>Schrodinger's intent was clearly to criticize the concept of the superposition
He INVENTED the very concept of superposition.

>Are you trolling?
Notice how he did not respond to anything I said.

>Holy fuck, you can't be serious. Throughout the thread I explained to you why this is wrong.
You: His point with the cat was that at no point the actual cat is in superposition.

What does "blurred reality" mean in this context? Provide a source. Or just fuck off already.

>He INVENTED the very concept of superposition.
Holy fuck you're dense. Schrodinger did not invent the Copenhagen interpretation, which states that a quantum system is in superposition until it is measured. This is what Schrodinger's cat attempts to show is absurd.

Ah. I'm sorry for miscommunicating, then; this argument has therefore been totally pointless and created by unclear writing on my part.

>What does "blurred reality" mean in this context?
It refers to the misconception of mistaking the wave function for the physical object itself. The wave function is a mathematical entity. The Copenhagen interpretation makes no claim about its ontological status. With "blurred variables" Schrödinger meant the wrong pop sci picture of thinking the wavefunction in superposition is identical with the actual cat being in superposition. This idea becomes absurd when considering the cat to be alive and dead "at the same time". In no way this disproves the formalism of wavefunctions however, only a wrong understanding of it. Why do I have to spell this out again, retard troll?

>Schrodinger did not invent the Copenhagen interpretation
Schrödinger introduced the concept of superposition to quantum mechanics. This is a historical fact you can find in any textbook.

>which states that a quantum system is in superposition until it is measured
The wavefunction is in superposition. Loosely speaking we say the quantum system is in superposition, but what we mean is the wavefunction, a mathematical object. As the cat shows, it is absurd to think of this mathematical object as being exactly the physical object instead of being merely a simplified abstract description of some of its properties. But then again you seem to be incapable of abstraction, so my posts are pearls before the swine.