I don't get Shrodinger's cat scenario, or by extension, quantum physics.

[fuzzybabybunny]

Sooo... the idea is that there's a cat in a box with some poison that could be released at any random time. Until we look inside the box, we don't know if the cat is alive or dead. Thus, when it is in the box, it can exist in two superimposed states, both alive and dead.

I totally don't get this. It seems to me that saying the cat is BOTH alive and dead is simply a way for us to say that we have no idea what's actually going on. We don't *know*.

What's actually going on is that the cat is actually in one of two states, alive or dead. Just because we don't *know* what state it's in doesn't mean that it's *not* in one of these two states. Opening the box and observing it shouldn't magically force it into being in one of two states.

Like... just because we don't know precisely how much fossil fuel we have left on this planet doesn't mean that there isn't a precise amount. It's just that we don't know. We don't know the exact coordinates of a bird flying overhead as we speak, but that doesn't mean that a bird's *not* there, flying overhead, at a certain coordinate. We just don't know about it.

Considering that I don't get this, I have a hard time wrapping my head around quantum mechanics and quantum computing. A single quantum bit (qubit) can be in multiple states at the same time instead of a 0 or a 1, like a classical bit. But how does this make sense? To me, all it means is we have no way of knowing what state it is actually in. It's still in a certain state at any point in time, we just don't know what it is. In quantum computing, how is it possible to use our complete lack of information to do actual computing?

 

[iCyborg]

You should read about double-slit experiment. The state of the cat is tied to the state of the particle, and quantum mechanics says that the particle is literally in *both* states before we observe it. You cannot explain double slit experiment if you assume that it's "actually" in one or another state and we just don't know. It has to be in both, hence the cat is also both dead and alive.

 

[blankslate]

Don't worry in an alternate universe another version of you understands it perfectly....


_____________

 

[flexy]

That's so funny because I JUST wanted to post about this on Discussion Club.

The "problem" understanding QT is that our perception of reality and QT is not exactly compatible.

In our reality, things "are". We form/create our reality by looking at things, observing or measuring.

This doesn't work in the Quantum world since the "looking" or the measuring itself creates the reality ("collapses the wave function") in our example it is the looking into the box.

We say the cat "is" either dead or alive - the problem is that the expression "is" doesn't apply in QT. "Is" refers to things which already HAVE become reality, after we observed them, after the wave function already collapsed.

From that point of view, even the thinking about the "state" of the cat BEFORE we observed it doesn't make sense respective is paradox. When we look at QT, we try to look in front of this veil of our reality, BEFORE things have "become" real, before things "are".

So..the best thing to deal with QT is to get away from applying our reality concepts to it, such as "it is"....because it doesn't work that way. This is how I understand it.

 

[swamplizard]

It is as you believe it is; it isn't as you believe it isn't. Or, not.

 

[flexy]

"We don't know the exact coordinates of a bird flying overhead as we speak, but that doesn't mean that a bird's *not* there"

I know it's hard to imagine this, but this is exactly what QT says, and until now no-one disproved this.

The double slit experiment shows that the outcome whether we measure a wave or a particle is decided by how we arrange the experiment.

There is no real photon that "is" a wave and no real photon that "is" a particle. There is no absolute reality that is "hidden" from us that will be "revealed".

(Which of course leads us to: There is no "real" cat that is either dead or alive)

Schrödinger's cat experiment was meant sort-of as a joke actually to point out the "silliness" of QT. We see and accept in QT that a particle's property/reality is created by measuring it. (In other words: WE create this reality, if you will)

What happens if we create some mechanism (Geiger counter to catch a decaying particle w/ 50% chance, poison, cat in box etc.) where the state of the cat is decided by this particle.? If we CREATE the reality of the particle only at the moment of measuring....logic says that we also create the reality of the cat (dead? alive?) ONLY THEN by "looking" (or measuring whether the particle decayed).

The question about the state of the cat "before" doesn't make sense...because "state of the cat" is a concept of our reality that only applies AFTER observation. The cat "is" not dead, it "is" not not-dead, not "alive", not "not-alive", in the same way as a photon is still not wave or particle BEFORE we check it. There is no hidden "real" state of the cat that we just have to determine. (Of course, common sense would say there is, but experiments like the double slit experiment prove that this thinking is wrong).

Yes it's totally confusing and "far out", but ONLY then if we apply our old-fashioned concepts to it.

 

[thesmokingman]

The cat is gonna die because the whatever poison is radioactive and is decaying. The question is when... boom head assplodes!

 

[KillerBee]

https://www.youtube.com/watch?v=j4XT-l-_3y0

 

[reallyscrued]

More helpful:

https://www.youtube.com/watch?v=DfPeprQ7oGc

 

[Greenman]

I thought the idea was that the cat existed as a probability field?

The entire concept seems rather silly to me, the cat is dead or alive. Open the box and look.

 

[Charmonium]

The double slit experiment shows that the outcome whether we measure a wave or a particle is already fixed, we decide this in how we arrange the experiment.

That's not really true. There are versions of the experiment where you can choose the state a photon is in AFTER it's state should have been determined. This is because in QM, the arrow of time does not apply. Things work just as well in reverse as they do going forward.

I can find some articles if anyone is interested but I'm kind of burnt right now.

 

[flexy]

That's not really true. There are versions of the experiment where you can choose the state a photon is in AFTER it's state should have been determined. This is because in QM, the arrow of time does not apply. Things work just as well in reverse as they do going forward.

I can find some articles if anyone is interested but I'm kind of burnt right now.

You are of course right, my explanation wasn't good, "fixed" is the wrong word in this context and misleading.

 

[Red Squirrel]

Yeah I think it's more a way of identifying the state, it's definitly in one or two states but because it's not known we just label it as being in the 3rd state. Kinda like a tri state transistor, when it's in the 3rd state, it's simply on or off, but we don't know, as opposed to being in a known state due to how much voltage the base is getting.

In a video game it might be different, in that the calculations made to determine the state might actually only happen when you open the box. So say you have a shrodinger's cat box in a game, it might be coded to only run the poison release algorithm and calculations at the time of being opened. It will perform all the delta calculations too, as if it had ran before. (ex: if it takes a certain amount of time for the poison to kill the cat).

In a real life situation you'd also know the cat is dead when it stops meowing and clawing at the box.

 

[werepossum]

You should read about double-slit experiment. The state of the cat is tied to the state of the particle, and quantum mechanics says that the particle is literally in *both* states before we observe it. You cannot explain double slit experiment if you assume that it's "actually" in one or another state and we just don't know. It has to be in both, hence the cat is also both dead and alive.

In a sense, the universe is being created as we need it, like a video game that only renders an object as we get close enough to view it. Until that time, the object exists in all possible states. But in another sense, every time we observe something, we limit its possibilities, so that the more we know about our universe, the less its freedom. Somebody needs to go back and look at all those particles to see if they resumed being waves once we stopped looking at them.

 

[Jaskalas]

More helpful:

https://www.youtube.com/watch?v=DfPeprQ7oGc

That's a great explanation of the dilemma. At a basic level.
Then there's the "blow your mind" next level.
https://www.youtube.com/watch?v=H6HLjpj4Nt4

 

[Jeff7]

Maybe there's something relevant in here somewhere...but I just like listening to this.
Some of his work was in quantum physics.


"...I think I can safely say that nobody understands quantum mechanics."

 

[mikeymikec]

I thought the idea was that the cat existed as a probability field?

The entire concept seems rather silly to me, the cat is dead or alive. Open the box and look.

This may result in Schrödinger's Scientist

 

[SKORPI0]

The entire concept seems rather silly to me, the cat is dead or alive. Open the box and look.

It is silly. You don't have to open the box, just shake the box/give it a kick. If the cat is alive it will meow, if dead no meow.

 

[TheELF]

It is silly. You don't have to open the box, just shake the box/give it a kick. If the cat is alive it will meow, if dead no meow.

Kicking the box will break the vial containing the poison thus killing the cat even if it where alive,that's the whole point of this thought experiment,you don't know the state (there is no state? ) unless you actively look at it.

 

[TheELF]

"...I think I can safely say that nobody understands quantum mechanics."

This!

 

[flexy]

No one denies that the cat "is" (or: becomes) either dead or alive, if we open the box, or when we kick the box. (All those things mean that we check on the state of the cat - how we do it doesn't matter.)

So yes, if we kick the box (or look into it), there will either be a dead cat or it'll be alive.

[Morpheus voice]
But what about the cat BEFORE we checked on it?
[/Morpheus voice]

The cat's well-being depends on the state of the atom (50% chance it decayed in a certain time), and QT proved (double slit experiment etc.) that atoms have no (better: take on a) "real" state UNLESS, and only then, once we look at it.

Since the cat's life depends on what's up with the atom (something we CAN not know before we measure) - so what about the cat? It cannot have a state independent from the atom. (Atom decayed = cat dead, atom not decayed: cat is fine)

 

[fuzzybabybunny]

That's a great explanation of the dilemma. At a basic level.
Then there's the "blow your mind" next level.
https://www.youtube.com/watch?v=H6HLjpj4Nt4

Ok, so to sum up the observations from the double slit experiment:

- photons are shot one at a time at the double slit

- there is a measuring device which determines which slit the photon went through

- with the device absent, the single-shot photons eventually create the interference pattern, indicating a wave. Say that there is an interference pattern of seven stripes. The first shot lands where line #4 is. The second lands where line #1 is, the third where #7 is, etc. It is only after a large number of shots are made that the seven stripe pattern emerges. It seems to me that in the absence of the measuring device, the photon acts like a wave.

- when the measuring device is placed *before* the slits and turned on, a two-stripe pattern emerges, indicating the photons now act like particles.

- when the measuring device is placed *before* the slits and turned off, a seven-stripe pattern emerges, indicating the photons have gone back to acting like waves.

Ok, whatever. Maybe the measuring device is somehow affecting the state of the photon before it reaches the slit, which explains the differences in patterns.

Now here's the weird part:

https://youtu.be/A9tKncAdlHQ?t=413

- when the measuring device is placed *after* the slits and turned on, a two-stripe pattern *still* emerges, indicating a particle, even though the measuring device is placed after the slits, after the slits should have already affected the state of the photon. Somehow the photon went through a slit, got measured, and proceeded to act like a particle.

- when the measuring device is placed *after* the slits and turned off, a seven-stripe pattern emerges. Somehow the photon went through a slit, didn't get measured, and proceeded to act like a wave.

This is where I get a bit lost - the Quantum Eraser

- the measuring device is placed *after* the slit and turned on and measures "which slit" the photon goes through

- the photons are shot and produce the two-stripe pattern

- but if the "which slit" information that the measuring device records is erased or obfuscate before the photon hits the screen, the seven-stripe pattern emerges.

 

[StrangerGuy]

The math is mighty hard but the concept is really straightforward: The act of observation affects the state of the physical system because it is fundamentally a part of the system, not outside of it. IMO it's only hard if you don't accept the fact that there are things that can be real which runs contrary to common sense.

 

[DigDog]

hopefully we will move away from schrodinger's cat because it's wrong; it stipulates that a human observer is different than a non-human observer. unless you believe in god, it's gotta be bullshit.
i'm calling it now like i called black holes destroying information, which hawking admitted is correct.

or we can start praying.

the experiment shows the results of the experiment; it's up to us to interpret it. see how badly we messed up with quantum entanglement - it turns out that the particles are, in fact, connected.


remember .. once upon a time, string theory was a thing.

 

[swamplizard]

This may result in Schrödinger's Scientist

:thumbsup::thumbsup: