Question about superpositions and the cat

[padren]

I searched and found this thread http://www.scienceforums.net/forums/showthread.php?t=15918 somewhat helpful, but there is a lot I don't understand so I have a few questions:

 

 

Schrodinger's cat:

I've read about this in wikipedia and looked at the Copenhagen interpretation as well as the Everett many-worlds interpretation, and there is some stuff I am having trouble clearing up. I think I may have read too many sources with "journalistic interpretation" throwing things off.

 

First, in the Copenhagen interpretation, the term "observer" is not nearly defined well enough for me. I believe the principle is that when you deal with anything Really Really Small the only way to observe it is to hit it with something (like a photon) which changes what the subject was up to in the first place.

If this is the case:

Isn't there a risk of naturally occuring photons altering the experiment in the same way, that are not part of any attempt to make an observation?

 

In the Schrodinger cat experiment, wouldn't the component in the experiment that "triggers the apparatus" imply an automatic observer system within the box?

 

I know it is observing the radiated particle and not the not-decaying/decaying nucleus, but isn't it effectively observing what state the nucleus was just in if it can detect an emmitted particle?

 

Is a superposition a literal state, or a way of mathmatically coping with the fact we can not observe the literal state and must deal with the probable range of states something can be in? (This is something I want to understand the most) I know the double slit experiment allows a photon or buckyball to act like its in two places at once, but is that the literal photon particle or the wave effect influence of the photon that is in two places at once?

 

Did Everett really say something to the effect that "when the box is opened, the universe is split into two separate universes, one containing an observer looking at a box with a dead cat, one containing an observer looking at a box with a live cat" and wouldn't that mean that every time any atom does or does not decays anywhere in the universe at any moment and is observed by impacting something else - that both possibilities would exist in seperate but existing universes?

Is there anything mathmatical on this, because it really sounds like a brain failing to cope and going semi-mystical, but I have trouble assuming Everett would say something like this without being able to back it up.

 

When people talk about quantum cryptography, is it effectively simular to writing a note on highly sensitive photonically/electron-ically combustable paper, where any reading device would cause the section read to burn and be destroyed as quickly as the text is determined?

Couldn't this be corrupted by any micro-interference that has the same overall effect of an observer, since an observer is not actually "a guy with eyes" in the literal sense?

[Klaynos]

First' date=' in the Copenhagen interpretation, the term "observer" is not nearly defined well enough for me. I [i']believe[/i] the principle is that when you deal with anything Really Really Small the only way to observe it is to hit it with something (like a photon) which changes what the subject was up to in the first place.

If this is the case:

Isn't there a risk of naturally occuring photons altering the experiment in the same way, that are not part of any attempt to make an observation?

 

It is always advisable to attempt to sheild your experiment from any outside influences including other photons. Those naturally occuring photons could in many cases be used to make an observation.

 

 

In the Schrodinger cat experiment' date=' wouldn't the component in the experiment that "triggers the apparatus" imply an automatic observer system within the box?

 

I know it is observing the radiated particle and not the not-decaying/decaying nucleus, but isn't it effectively observing what state the nucleus was just in if it can detect an emmitted particle?

[/quote']

I can't remember the exact trigger mechanisim so can't really comment on this, sorry.

Is a superposition a literal state' date=' or a way of mathmatically coping with the fact we can not observe the literal state and must deal with the probable range of states something can be in? [i'](This is something I want to understand the most) I know the double slit experiment allows a photon or buckyball to act like its in two places at once, but is that the literal photon particle or the wave effect influence of the photon that is in two places at once?[/i]

 

It is a superposition state, whilst in this the system is in the state of superposition, the state of not knowing you could say.

 

Did Everett really say something to the effect that "when the box is opened' date=' the universe is split into two separate universes, one containing an observer looking at a box with a dead cat, one containing an observer looking at a box with a live cat"[/i'] and wouldn't that mean that every time any atom does or does not decays anywhere in the universe at any moment and is observed by impacting something else - that both possibilities would exist in seperate but existing universes?

Is there anything mathmatical on this, because it really sounds like a brain failing to cope and going semi-mystical, but I have trouble assuming Everett would say something like this without being able to back it up.

 

I'm not sure of the quote, and often these things become lost to urban myths and here say. What I will say though is that alot of people belive in the idea of a multiverse in which every possibility that could of happened does happen in another universe.

 

When people talk about quantum cryptography' date=' is it effectively simular to writing a note on highly sensitive photonically/electron-ically combustable paper, where any reading device would cause the section read to burn and be destroyed as quickly as the text is determined?

Couldn't this be corrupted by any micro-interference that has the same overall effect of an observer, since an observer is not actually "a guy with eyes" in the literal sense?[/quote']

Again my memory is failing me on the mechanisism of quantum encryption, but again it could be effected by outside influcences chaning the quantum state of componants, but there would be attempts to shild against this and the probablility is probably very low.

[5614]

In the Schrodinger cat experiment, wouldn't the component in the experiment that "triggers the apparatus" imply an automatic observer system within the box?

The trigger is a radioactive sample which if decays sets of a trigger. The reason a radioactive sample is used is because it is random, there is an exact 50% chance it will decay and it is a true random process. What observer is there in something radioactive decaying?

 

Is a superposition a literal state

Sadly yes.

(sadly because it's illogical (and so hard to understand and accept) to our "classical physics" minds).

 

You say you know about the double slit, well that's easiest way to explain the "yes". If the photon went only through one hole and we didn't know which, then it wouldn't produce the right interference pattern. The photon can't interfere with itself if it is only in one place, it must be in two places and those two places interfere with each other, this produces the famous double slit pattern.

 

It can be easier to picture light, in this case, as a wave. So in the image below it appears simple that one wave can go through 2 holes:

 

 

The light is diffracted through the single slit so it can spread out and cover the whole of the double slit screen. Then as you can see each wave will proceed to go through both holes. Similar thing here:

http://img.photobucket.com/albums/v601/5614/doubleslit2.jpg

The problem arises when people try to quantise this image, as in they try to imagine a single photon, a body, a little dot, now how can you imagine a single dot in two places?!? Quite honestly you cannot, and this is why you cannot imagine, as such, quantum physics... it's why QM is hard and some people don't like or want to accept it.

 

Even Einstein disagreed with part of QM (in his famous EPR Paradox)... a while after Einstein's death Bell (in Bells Theorem or Inequality) proved the EPR Paradox and thus Einstein incorrect, so QM is correct.

 

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I don't follow what you mean about the quantum cryptography thing.

[padren]

The trigger is a radioactive sample which if decays sets of a trigger. The reason a radioactive sample is used is because it is random' date=' there is an exact 50% chance it will decay and it is a true random process. What observer is there in something radioactive decaying?

[/quote']

Well, we use detectors of sorts to observe these things, and some sort of detector has to be there to flip the trigger. If the equipment to observe the 50% chance of decay was not inside the box, the trigger could not be set off.

 

Also, by random, I am assuming we mean that the actual causative one way or the other is based on factors too small to measure, and thus probability and "range of possibilties" becomes more useful than just saying we can't observe the cause, as we can then still work with ranges at least.

 

Sadly yes.

(sadly because it's illogical (and so hard to understand and accept) to our "classical physics" minds).

 

You say you know about the double slit' date=' well that's easiest way to explain the "yes". If the photon went only through one hole and we didn't know which, then it wouldn't produce the right interference pattern. The photon can't interfere with itself if it is only in one place, it must be in two places and those two places interfere with each other, this produces the famous double slit pattern.

 

It can be easier to picture light, in this case, as a wave. So in the image below it appears simple that one wave can go through 2 holes:

 

[img']http://img.photobucket.com/albums/v601/5614/doubleslit1.jpg[/img]

 

The light is diffracted through the single slit so it can spread out and cover the whole of the double slit screen. Then as you can see each wave will proceed to go through both holes. Similar thing here:

http://img.photobucket.com/albums/v601/5614/doubleslit2.jpg

The problem arises when people try to quantise this image, as in they try to imagine a single photon, a body, a little dot, now how can you imagine a single dot in two places?!? Quite honestly you cannot, and this is why you cannot imagine, as such, quantum physics... it's why QM is hard and some people don't like or want to accept it.

 

Even Einstein disagreed with part of QM (in his famous EPR Paradox)... a while after Einstein's death Bell (in Bells Theorem or Inequality) proved the EPR Paradox and thus Einstein incorrect, so QM is correct.

 

Thanks for the feedback.

 

In the double slit experiment, if you had the slits cut into a solar panel of sorts, would you find the photon only passed through one of the two slits, or would it also have gotten absorbed by the wall the slits are in too?

 

Even if it is in more than one place at once, it can't, I assume, have more energy than a single photon, or impart less than a single quanta of photon-sized energy into anything that absorbs it.

 

 

So, if I understand, there is a wave form, which is a spatial range of where the photon particle is.

 

How do you throw a single photon in a straight line at one slot, and have it pass through a slot several degrees off course?

 

Do particle accelerators limit the range of this factor? It seems they are very specific and accurate in how they sling particles around, and if the double slit works with buckyballs how does this get factored in accelerators using smaller particles?

 

 

Is it possible a particle is a side effect - a way of reacting - when something that is more generally a wave is impacted by a force large enough to observe it, the wave's energy gets particlized at that point of impact? (wild speculation of course, I am trying to figure out if these behaviors in QM are consistent with anything that makes more general sense to me, but naturally I am sure thats a long shot)

[5614]

Radioactive sample:

 

The trigger is the radioactive sample decaying. If it decays thing it emits (through the decaying process) triggers the trigger.

 

Radioactive decay is a truely random event. That is, it is totaly random. It is probably the single example of true randomness.

 

In the double slit experiment, if you had the slits cut into a solar panel of sorts, would you find the photon only passed through one of the two slits, or would it also have gotten absorbed by the wall the slits are in too?

If the photon is deteced on the detector screen then it must have gone through a hole (or 2, depending on the setup), however obviously when bombarding the 2 slits with photons some of the photons will bounce off the screen, or be absorbed by the solar panels in this case, these photons will not then be detected by the detector screen.

 

Even if it is in more than one place at once, it can't, I assume, have more energy than a single photon, or impart less than a single quanta of photon-sized energy into anything that absorbs it.

It cannot have more energy than one photon, E = hf, energy of a photon is equal to Planck's constant multiplied by the frequency of the photon.

 

How do you throw a single photon in a straight line at one slot, and have it pass through a slot several degrees off course?

It is a wave, not a straight line. And the wave covers both holes. If the experiment was setup that the wave could only get through one slit then it would be a normal one slit diffraction which is observed. Similarly in our double slit experiment there may be thousands of slits thousands of miles away from the 2 we are using, they are irrelevant.

 

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I don't follow you with the particle accelerators. Physicists can accurately guide particles with a known mass and known charge in a particle accelerator because they know the mass and charge they can work out the magnetic field required to move the particle.

 

when something that is more generally a wave is impacted by a force large enough to observe it, the wave's energy gets particlized at that point of impact?

QM doesn't really talk about things being a wave or a particle, QM considers a particle as "something" a combination or both wave and particle properties, there is no such thing as a literal wave-particle duality what really describes particles is a 3rd "thing".

 

So if a wave was impacted by a force (can we assume another wave?) then what happens really does depend on the nature of the waves, their energy, etc.

 

If an electromagnetic wave is big enough it can split into an electron/positron pair... but that isn't really a "wave's energy gets particlized".

 

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Back to the double slit, understand that you can never observe an electron going through both holes at once. As soon as you try to observe where the electron goes (no matter how you try, trust me, physicists have tried damn clever methods trying to trick the electrons!) the electron will, if observed, go through one hole and then you get the normal single slit diffraction results.

 

If you have the two slits and you are observing both slits then each electron again goes through one hole (because when you observe you are taking the electron out of it's superposition, you are collapsing its wavefunction (same as saying it's no longer in superposition)) and the end result is that you get two lots of single slit results ontop of each other. Note this is different from the normal double slit where the waves interfere. If you observe the electron must go through one hole and so cannot go through both and so cannot interfer with itself and so you don't get the unusual double slit results.