Quantum Cat

[s pepperchin]

When I took undergrad Physics the cat was used to explain why when we pass light through a double slit we see a diffraction pattern, but if we place a detector at one of the slits to tell us when the particle passes through that particular slit we get a pattern as if there is only one slit.

 

The reason for this is because as long as we give the particle a "choice" of paths then there is a probablity that the particle will pass through each slit, then on to the screen. When we place a detector there then we change the system, this change comes from the fact that we can not detect a particle without causing some change in the particle. and this is the essence of the cat experiment.

 

To recap, there is a probability associated with the cat being alive as well as one with the cat being dead. As soon as we open the box to look inside we see which one it is. I hope my explanation is sufficient.

[swansont]

When I took undergrad Physics the cat was used to explain why when we pass light through a double slit we see a diffraction pattern' date=' but if we place a detector at one of the slits to tell us when the particle passes through that particular slit we get a pattern as if there is only one slit.

 

The reason for this is because as long as we give the particle a "choice" of paths then there is a probablity that the particle will pass through each slit, then on to the screen. When we place a detector there then we change the system, this change comes from the fact that we can not detect a particle without causing some change in the particle. and this is the essence of the cat experiment.

 

To recap, there is a probability associated with the cat being alive as well as one with the cat being dead. As soon as we open the box to look inside we see which one it is. I hope my explanation is sufficient.[/quote']

 

I believe you have the situation backwards, though. The cat isn't being used to explain the "which-path" experiment; QM explains that perfectly well on its own. There is no classical scenario in which you can state that a cat is both alive and dead at the same time. The conundrum of Schroedinger's cat is that we know that if the cat died, it did so (classically) whenever the 50% probability event took place, but the wave function doesn't collapse to that state (or the other) until we open the box and look.

[Connor]

the cat is supposed to make that sort of scenario easier to understand, though, as a thought experiment

[Klaynos]

the cat is supposed to make that sort of scenario easier to understand, though, as a thought experiment

 

I always thought it just conufuses matters, I've only had it mentioned to me as a reason of why QM seems silly on the macro scale, never used it to help understanding and it hasn't been mentioned since starting undergrad degree...

[Dark Photon]

I always thought it just conufuses matters, I've only had it mentioned to me as a reason of why QM seems silly on the macro scale, never used it to help understanding and it hasn't been mentioned since starting undergrad degree...

 

HAHA... quote matters!! do you get it? matter!! HAHAHA

[swansont]

the cat is supposed to make that sort of scenario easier to understand, though, as a thought experiment

 

All I can say is that it has never been presented that way in any class with which I have been associated, either sitting or standing. So my experience differs from yours.

[Specusci]

Sorry to interrupt again...perhaps another thread could be made elsewhere for this...but when people say "Maths", it sounds somewhat...erm...simple. Simple, as in, "Look pa! I gots a fifties in my maths work!". No offense. Its just that I've never seen "maths" used in formal english...math maybe, but the extra S? C'mon...

[Connor]

okay

 

in America, where I live, mathematics is shortened math

in England and elsewhere, it is maths

 

get over it, it's different. I find myself switching between the two

 

just because you're not used to it doesn't make it "simple"

[Sashatheman]

I Dont understand how this cat experiment is ment to explain the quantum uncertainty on a macro level. I dont see how a cat is said to be in a super-position. I understnd that the decay of that particle is absolutly random and we cant be certain if it happened or not. I also agree that before we open the box we are not certain if the cat is dead or alive, but i cant understand why that has to mean that the cat is in super-position.

 

How is this example i am gonna give any differnt to the cat experiment

 

i have a random number generator on the computer, but only generates 0 or 1. i dont know what number is gonna be next, but if it zero then the computer crashes, if its 1 its gonna be fine. why cant we say the computer is in super-position, if that random number event occured when i wasnt in the room.

[5614]

The computer is in a superposition.

 

It is best to stick to the radiation example because radiation is totaly random. Radioactive decay is the only truly random process. A computer must base it's random numbers on something and that something cannot be random and so no computer can ever produce a true random number. It can bring up "random" numbers and they may seem as random as radioactive decay, but it is a computer and it must calculate the "random" number (using some other number) and so it's not technically truly random.

 

What part of the cat don't you understand? How a cat can be alive and dead... or what superposition actually means?

 

Superposition:

This quite simply means that something (maybe a cat) could be in a variety of different states (ie. dead or alive) and we don't know which because we haven't looked at (or observed) it (the cat). Superposition goes further to say that it is NOT that the cat is either dead or alive, superposition says that the cat IS dead AND alive (at the same time).

 

Cat alive and dead:

The problem with this is that when you think of a cat you think using the logic of classical physics. However the experiment is meant to show a quantum mechanics effect. Thinking in the everyday sense of "logically" is pointless because the logic is classical and not quantum. Imagining the cat of alive AND dead at the same time is impossible, because the imagination is also classical.

 

This is where I feel the experiment breaks down, because when you try and explain it to people they can't accept (ie. imagine) that a cat is both dead and alive, if this is the case it may be best to forget the cat and move onto particles - people seem to find it easier to accept that a particle is spinning up and down rather than a cat being dead and alive.

[s pepperchin]

If you want to use the computer as an example than it would work. The reason you could use it is that if the computer is in the other room and you know that there is a probabilty that the computer gets a 1 or 0 than thats all you have is a superposition of the probabilties of 1 or 0. When you open the door and look at the computer than the superposition of probabilities collapses to one of the two outcomes, just like the cat is alive or dead before you look in the box.

[Sashatheman]

i Just dont understand how people can answer this superposition with the theory of multverses where alot of things are very equal, but in one universe the cat is alive, in the other the cat is dead.

 

when i read about this experiment (this was before i came to this thread) , i can amagine the decay being totally random, but i just see the cat as being somethign that gets effected by this random decay, and thats it.

 

 

I dont see how us not knowing the exact result can be justified for many universes.

[5614]

The theory of a multiverse still works.

 

In one multiverse the cat is dead... in another the cat is alive. The trick is that we are in a 3rd or in between the two. We are in a superposition between the two multiverses.

 

When we observe the cat we break the superposition the cat is in and we also break the superposition that we are in (ie. which of the multiverses we are in).

[Dark Photon]

any one know where i can get the equipment used in youngs double slit experiment?

[s pepperchin]

Go here:

 

http://www.pasco.com/

 

They sell all kinds of scientific lab equipment.

[swansont]

The theory of a multiverse still works.

 

In one multiverse the cat is dead... in another the cat is alive. The trick is that we are in a 3rd or in between the two. We are in a superposition between the two multiverses.

 

When we observe the cat we break the superposition the cat is in and we also break the superposition that we are in (ie. which of the multiverses we are in).

 

 

I think one view is that the additional universe is created when the measurement is actually made. You have one universe (looking only at this one scenario) during the superposition, and then one for alive and one for dead.

[s pepperchin]

The idea is that all of the multiverses exist and we are in all of them but everytime we make a decision we take a measurement of sorts. It is that decision which collapses all of the multiverses of the future that share that moment into one.