Reality exists when observed, but who is the observer?

[ExNihilo]

Hi,

Reading about quantum mechanics, the probability wave is so that a particle can be everywhere. But when observed, it's probability wave collapses and the particle has to take a definite state.

The example were given for Schrödinger's cat, which is either alive or dead only after we open the box to look at it. Other examples could be that the moon might not exist in the sky if no one look at it. Or a tree falling in the forest is not really falling if no one checks it.

What is the power of the observer to dictate a behavior to a quantum particle? In other words, why would the state of dead/alive of Schrödinger's cat materializes only when I look at it while the cover of the box was actually staring at it the whole time?

In the case of the moon, how come it materializes at the same position while there are billions of different of conscious observers? And on top of that, its position is even predictable.

Thanks for any clarification.

 

[mathman]

You shouldn't take these examples too literally. What collapses a wave function is an interaction with something. The "looking" idea is meaningful in that it is necessary to shine a "light" on something to see it.

 

[pallidin]

The "looking" idea is meaningful in that it is necessary to shine a "light" on something to see it.

The solar cells on my house in no way changes the original or subsequent emission of photons from the sun itself.
"That's my story and I'm sticking to it.."

 

[Drakkith]

Does a cat count as an observer? It does to me. As does all life. Even particles themselves are "observers" to me. I don't believe that there is something special that somehow makes us the masters of reality compared to the rest of the universe.

 

[ExNihilo]

Does a cat count as an observer? It does to me. As does all life. Even particles themselves are "observers" to me. I don't believe that there is something special that somehow makes us the masters of reality compared to the rest of the universe.

That is exactly what I wondered. Looking at something doesn't alter in any way the energy of the observed particle. And how does it know it is observed by someone or something? For example, a star distant at X light years away has no idea if it is observed.

BTW, the argument of shining light is not convincing. From Earth, no one can look at the dark side of the moon and there is plenty of light there. From the number of craters all over the moon, it did exist well before anyone can look at it.

It is more probable that I didn't fully understand what I read. I really have hard time to see how the act of observing could transform a probable reality to a permanent and unalterable one.

 

[coelho]

Well... when we think we are starting to understand something about quantum mechanics, it confuses us again... look at:

http://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser

 

[Pezmo]

Dimensions = Direction of awareness. A 4th dimensional (spatial time) awareness exists on a 5 dimensional plane of possibilities. A 4th dimensional entity touches down into the 3rd dimension, swiping itself through time, whos awareness gets enveloped into the conscious beings that exist on the 3D plane giving a sense of "me" or "I" through the ego (self consciousness is awareness being drawn from outside, in). Manifestation and "free will" happen when the conscious being strongly wishes, urges or feels a certain way, swaying the 4th dimensional awareness to move through the 5 dimensional plane of possibility.

Everything exists always, there is a perceived beginning and end if perceiving time, however everything ever that is 3 dimensional exists on its plane of existence, through infinite timeless moments and paralleling timeless possibilities. the conscious observer as one is moving through time (at the same speed because it is one) thus we all have a reality to share in this "now" that is infinitely long and eternally fleeting. It doesn't matter if there is a conscious observer to see if something happens or not, if a conscious being happens to be there though, he sees the timeless moments strung together into a film to be observed as an experience through our brains neurons who reach threshold up to 100 times a second (one hundred conscious moments a second = average speed of 4th dimensional awareness through time) who is only aware of roughly 40 timeless moments per second unless awareness is heightened through adrenaline or drugs (this causes us to perceive time slower due to perceiving more timeless moments a second)

 

[skippy1729]

There is no universal agreement on the answers to your questions. If you are looking for a popular answer, you will not find it here. This is the one that works for me:

"In our description of nature the purpose is not to disclose the real essence of the phenomena but only to track down, so far as it is possible, relations between the manifold aspects of our experience" Niels Bohr

MY wavefunction of the cat is based on all the information I have about the classical experimental apparatus including MY knowledge of the preparation of the isotope used for the trigger &ct. I will calculate probabilities for cat-alive and cat-dead as functions of time. You may calculate YOUR wavefunction, based on all of YOUR information. It may or may not be identical to mine. You may have slightly different information. When I open the box I will acquire new information, namely cat-alive or cat-dead. I will use my new information to update MY wavefunction to a pure state |cat-alive> or |cat-dead>. If you happen not to be in the room YOUR wavefunction will not change. You might come into the room later and update YOUR wavefunction to a pure state. You might call me on the telephone and get new information. Based on this information you could update YOUR wavefunction to a pure state (if you trust me) or to a new mixed state (if you have reservations about my honesty).

The "cover of the box" doesn't have a wavefunction as it is incapable acquiring and processing the information to build one.

MY wavefunction is about MY information. YOUR wavefunction is about YOUR information. THE wavefunction exists only as a mathematical abstraction in school-book exercises: "Given a hydrogen atom in the ground state, calculate...".

Advantages of this viewpoint:

1. Less sleepless nights dwelling on non-problems.

2. More sleepless nights dwelling on real problems.

3. If there are aspects of quantum theory which cannot be explained by this approach then they might contain a clue to the underlying physical phenomena.

4. There are no, in principle or in fact, unobservable metaphysical entities to cloud our picture of the world.

As for the moon, I agree with Von Weizsacker:

"What is observed certainly exists, about what is not observed we are still free to make suitable assumptions. This freedom is then used to avoid paradoxes."

I use my freedom to assume that the moon is there when I am not looking. So far, this has not lead to a paradox.

Skippy

 

[unusualname]

The simple answer to your question, is that reality exists even if it is not observed, but it is a probabilistic reality, so if no one observes it, no one can know what it is. If an amoeba observes it then that just isn't so great, since the amoeba can't create a subsequent macroscopic record like a paper on arXiv to explain its observation or even a discussion in starbucks.

 

[San K]

Observation does not collapse the wavefunction. It's various kinds of "interactions/setups" that collapse it.

 

[pallidin]

"Constrained" probability likely exists in reality.
Else a free-for-all would be present; which we do not see at all.

 

[Dmitry67]

another example how Copenhagen Int does more harm than good...

 

[skippy1729]

another example how Copenhagen Int does more harm than good...

Here is a 30 second discussion of CI that you will enjoy. It is a hoot!

 

[Varon]

There is no universal agreement on the answers to your questions. If you are looking for a popular answer, you will not find it here. This is the one that works for me:

"In our description of nature the purpose is not to disclose the real essence of the phenomena but only to track down, so far as it is possible, relations between the manifold aspects of our experience" Niels Bohr

MY wavefunction of the cat is based on all the information I have about the classical experimental apparatus including MY knowledge of the preparation of the isotope used for the trigger &ct. I will calculate probabilities for cat-alive and cat-dead as functions of time. You may calculate YOUR wavefunction, based on all of YOUR information. It may or may not be identical to mine. You may have slightly different information. When I open the box I will acquire new information, namely cat-alive or cat-dead. I will use my new information to update MY wavefunction to a pure state |cat-alive> or |cat-dead>. If you happen not to be in the room YOUR wavefunction will not change. You might come into the room later and update YOUR wavefunction to a pure state. You might call me on the telephone and get new information. Based on this information you could update YOUR wavefunction to a pure state (if you trust me) or to a new mixed state (if you have reservations about my honesty).

The "cover of the box" doesn't have a wavefunction as it is incapable acquiring and processing the information to build one.

MY wavefunction is about MY information. YOUR wavefunction is about YOUR information. THE wavefunction exists only as a mathematical abstraction in school-book exercises: "Given a hydrogen atom in the ground state, calculate...".

Advantages of this viewpoint:

1. Less sleepless nights dwelling on non-problems.

2. More sleepless nights dwelling on real problems.

3. If there are aspects of quantum theory which cannot be explained by this approach then they might contain a clue to the underlying physical phenomena.

4. There are no, in principle or in fact, unobservable metaphysical entities to cloud our picture of the world.

As for the moon, I agree with Von Weizsacker:

"What is observed certainly exists, about what is not observed we are still free to make suitable assumptions. This freedom is then used to avoid paradoxes."

I use my freedom to assume that the moon is there when I am not looking. So far, this has not lead to a paradox.

Skippy

On a monday I thought of what you just described. But on a tuesday I entertain Many Worlds where the Wave function is literal and the cat being alive and dead really occurs. On a wednesday. I entertain Bohmian Mechanics where wave function has ontological reality but just informaiton... I'm so fickled minded when it comes to Interpretations. I can't seem to decide what to choose.

About what your describe above that it's just information of the observer. But there is interaction with the observed. For example. In the absence of measurement to determine its position, the electron has no position. And your information update of the wave function should be more complicated (than what you described) because it is interactive with something that appear only when observed. Incidentally, I read what you described is called the Ignorance Interpretations proposed at Solvay Congress 1927 and debunked by Dirac because of what I just mentioned.

 

[Fredrik]

another example how Copenhagen Int does more harm than good...

I couldn't agree more.

(I'm assuming that we're defining the CI as "QM plus the assumption that a wavefunction is a complete description of all the properties of a single system", or something very similar to that).

People need to start thinking of QM as an assignment of probabilities to possible results of experiments, instead of as a description of what's actually happening. QM doesn't have a measurement problem. The CI, as defined above, does.

 

[Varon]

I couldn't agree more.

(I'm assuming that we're defining the CI as "QM plus the assumption that a wavefunction is a complete description of all the properties of a single system", or something very similar to that).

People need to start thinking of QM as an assignment of probabilities to possible results of experiments, instead of as a description of what's actually happening. QM doesn't have a measurement problem. The CI, as defined above, does.

But accepting this QM as mere assignment of probabilities to possible results of experiments won't tell you why a particle can interfere with itself in the double slit. So your proposal is trying to suppress other information by focusing only on the primary one. It may work but this is incomplete physics.

 

[Fredrik]

But accepting this QM as mere assignment of probabilities to possible results of experiments won't tell you why a particle can interfere with itself in the double slit. So your proposal is trying to suppress other information by focusing only on the primary one. It may work but this is incomplete physics.

There's no reason to think that QM contains an answer to the question of why a particle "interferes with itself". (Actually, I wouldn't say that a particle does interfere with itself. I would say e.g. that all the paths from the emitter to the detector must be included in the calculation of the total amplitude for detection. Your way of saying it suggests very strongly that we have identified the wavefunction with the actual particle, and that's exactly what I don't want to do, because that's the assumption that's causing most of the confusion about QM).

If you're going to make unjustified assumptions that change QM into something that does contain the answer, then what are you really accomplishing? This is like having a statement "B" that you're uncomfortable leaving unproved, and you know that "A implies B" is true, but you don't know if "A" is true, so you just assume that "A" is true and then claim that you have derived "B" as a theorem. How is it better to assume "A" instead of "B"?

 

[Varon]

There's no reason to think that QM contains an answer to the question of why a particle "interferes with itself". (Actually, I wouldn't say that a particle does interfere with itself. I would say e.g. that all the paths from the emitter to the detector must be included in the calculation of the total amplitude for detection. Your way of saying it suggests very strongly that we have identified the wavefunction with the actual particle, and that's exactly what I don't want to do, because that's the assumption that's causing most of the confusion about QM).

If you're going to make unjustified assumptions that change QM into something that does contain the answer, then what are you really accomplishing? This is like having a statement "B" that you're uncomfortable leaving unproved, and you know that "A implies B" is true, but you don't know if "A" is true, so you just assume that "A" is true and then claim that you have derived "B" as a theorem. How is it better to assume "A" instead of "B"?

Let's this is how it can be scrutinzed.. by analyzing a one particle at a time double slit experiment. Instead of the particle also being wave and interfering with itself. You mentioned about "all the paths from the emitter to the detector must be included in the calculation of the total amplitude for detection", so instead of the particle turning into a wave. It literally takes all path and the final interference of the single particle is caused by this? This is even more bizarre than the particle turning into wave. If you'd say it is just mathematical. Pls. explain why it could be since an actual particle is emitted. Unless only measurement make sense because somehow the universe before measurement is in some processing unit in some distant surface boundary courtesy of the Holographic Principle.

 

[Fra]

There's no reason to think that QM contains an answer to the question of why a particle "interferes with itself".
...
If you're going to make unjustified assumptions that change QM into something that does contain the answer, then what are you really accomplishing?

This is the issue again of "pure interpretations". I agree that at the end of the day these pure interpretations makes no difference.

But if we think QM needs modification and generalisation in order to solve the open issues of QG and unification, then I think there is something to accomplish. But it's not evident as long as the discussions stays at the "interpretation-only" level.

IMHO, there is one very SIMPLE way to actually understand what interfering with yourself means:

In my tweaked version of the information interpretation, the action of an observing system depends on the systems own EXPECTATIONS of the future. This is a little bit like the master always says to the student in old martial arts movies :) "The enemy is not in front of you, he is in your head". This is actually partly true, because your own actions really ARE influence by your OWN expectations of your environmen. You can CHANGE the behaviour of a system, simply by chancing it's expectations of you.

This is how I think of this, and self-interference makes good sense.

Then what difference it makes, is I think not obvious at this point but this is the only way I've found to try to generalize measurment theory to one that is intrinsic and applies also to cosmological scale scenarios.

/Fredrik

 

[Varon]

This is the issue again of "pure interpretations". I agree that at the end of the day these pure interpretations makes no difference.

But if we think QM needs modification and generalisation in order to solve the open issues of QG and unification, then I think there is something to accomplish. But it's not evident as long as the discussions stays at the "interpretation-only" level.

IMHO, there is one very SIMPLE way to actually understand what interfering with yourself means:

In my tweaked version of the information interpretation, the action of an observing system depends on the systems own EXPECTATIONS of the future. This is a little bit like the master always says to the student in old martial arts movies :) "The enemy is not in front of you, he is in your head". This is actually partly true, because your own actions really ARE influence by your OWN expectations of your environmen. You can CHANGE the behaviour of a system, simply by chancing it's expectations of you.

This is how I think of this, and self-interference makes good sense.

Then what difference it makes, is I think not obvious at this point but this is the only way I've found to try to generalize measurment theory to one that is intrinsic and applies also to cosmological scale scenarios.

/Fredrik

Translate this to a single particle double slit experiment. So the observing system is the detector. And you said "the action of an observing system depends on the systems own EXPECTATIONS of the future." You make it sound like the particle is alive. Just explain how the particle can form destructive interference after million of single hits. The devil is at the details as they say. So you are like saying "the action of the detector depends on the particle own EXPECTATIONS of the future"?? So in your view, a particle can think? You didn't make much sense.

 

[Fra]

Translate this to a single particle double slit experiment. So the observing system is the detector. And you said "the action of an observing system depends on the systems own EXPECTATIONS of the future." You make it sound like the particle is alive. Just explain how the particle can form destructive interference after million of single hits. The devil is at the details as they say. So you are like saying "the action of the detector depends on the particle own EXPECTATIONS of the future"?? So in your view, a particle can think? You didn't make much sense.

With particles EXPECTATIONS and the detectors EXPECTATIONS I mean what's implicit in the physical STATE of the particle and the detector.

I'm using the analogy with humans to illustrate the principle only. No I don't suggest observers "think". The particles action is completely random. From the inside view I think the partilces just does a "random walk", it does not think at all of course. But, the random walk takes place relative to the system of mictrostructures that defines the particle itself.

> "the action of the detector depends on the particle own EXPECTATIONS of the future"

I think the INSTANT action of the detector depends on the DETECTORS expectations of the particle. The finite action of the detector depends on the full "interaciton" between particle and detector. I think the "potentialities" for the interference is there always in a single particle, due to the idea that the system responds to it's own expectations (instantly or infinitesimally), but it's still true that in order for use to see it, we need many particles. But this is no more weird that the fact that you need to throw a dice several times to see it's prior. One or two throws does not reveal. But the potentialities is still in the single dice.

All I was commenting is that I personally doe not have any problems to conceptualize what "self-interference" means.

With Expectations I do not refer to thinking particles. I think of it as random walks. But the random walks is relative to the observer, this is why while I am doing a random walk (on step at a time; thinking I follow the easiest path forward) an outside observer can see that I am following a curved path. Here with path I mean a generalizaion from spacetime and path can mean a path in a general state space.

/Fredrik

 

[Varon]

With particles EXPECTATIONS and the detectors EXPECTATIONS I mean what's implicit in the physical STATE of the particle and the detector.

I'm using the analogy with humans to illustrate the principle only. No I don't suggest observers "think". The particles action is completely random. From the inside view I think the partilces just does a "random walk", it does not think at all of course. But, the random walk takes place relative to the system of mictrostructures that defines the particle itself.

> "the action of the detector depends on the particle own EXPECTATIONS of the future"

I think the INSTANT action of the detector depends on the DETECTORS expectations of the particle. The finite action of the detector depends on the full "interaciton" between particle and detector. I think the "potentialities" for the interference is there always in a single particle, due to the idea that the system responds to it's own expectations (instantly or infinitesimally), but it's still true that in order for use to see it, we need many particles. But this is no more weird that the fact that you need to throw a dice several times to see it's prior. One or two throws does not reveal. But the potentialities is still in the single dice.

All I was commenting is that I personally doe not have any problems to conceptualize what "self-interference" means.

With Expectations I do not refer to thinking particles. I think of it as random walks. But the random walks is relative to the observer, this is why while I am doing a random walk (on step at a time; thinking I follow the easiest path forward) an outside observer can see that I am following a curved path. Here with path I mean a generalizaion from spacetime and path can mean a path in a general state space.

/Fredrik

Why are you making it much more complicated. Why not just accept the Copenhagen explanation that after the particle is emitted, it doesn't have any position even in principle.. and it morphs into a wave and upon exiting the slits, the wave reconstitute into a particle after it reached the detector. What's wrong with this picture? You don't accept it? Which part don't you accept and why?

Or maybe you accept that the wave function is just the knowledge of the person doing the experiment? This doesn't make sense because it implies the particle didn't turn into a wave when unobserved. It just avoids the question of what happens to the electron.

Btw.. you keep mentioning about observers. In the double slit. Is the observer the detector or the person performing the experiment?

 

[Fra]

> Why are you making it much more complicated. Why not just accept the Copenhagen explanation that after the particle is emitted, it doesn't have any position even in principle.. and it morphs into a wave and upon exiting

The reason I complicate it, is because I'm aiming at more than just an interpretation. I'm aiming to understand the origin of the interactions themselves (ie. what is usually put in manually as an hamiltonian och lagrangian) and this ultimately suggest a generalisation of QM. In order to do that, I am looking for the simply inside view. Then the more complex eternal view (usually encoded as a lagrangian etc) should be inferrable from the inside view, by means to evolving the theory to a more complex scale.

Ie. Rather than starting from a classical lagrangian, and then "quantize" (in which case you can not explain/understand the interactions and in particular no unification in terms of inference), I am trying to understand all interactions in terms of what I call "rational action" which is the action you get when you make a random walk in the INSIDE VIEW. This random walk takes place in the inferred state space, This ultimately views ALL interactions as emergent as per an entropic construction. From the inside view, all there is are random walks. The more complex (certainl not random ones) are what you see when a second observer, rationally infers the action from another perspective.

If someone is happy with starting with a classical system and then quantize ok fine, but I am not. I'm trying to do more than just "interpret QM" for small subsystems, because to me, the questions are related.

I have nothing to add to the pure interpretational discussion. Some people try to "interpret QM" without going too deep, and without trying to think that the problems of unification and QG has anything todo with the foundations of QM. I think they do.

> Or maybe you accept that the wave function is just the knowledge of the person doing the experiment? This doesn't make sense because it implies the particle didn't turn into a wave when unobserved.

No I don't think the wavefunction refers to human knowledge. I agree it makes no sense.

> Btw.. you keep mentioning about observers. In the double slit. Is the observer the detector or the person performing the experiment?

The observer is not unique, and if you change the observer, the description of the measurement changes. Each experiment can be described by different angles (observers). In my view, there are "many observers" which are interacting, not many worlds or ensembles.

Interactions in general are then EXPLAINED as "interactions" between different observers. This is MY view. And it's aims to explain much more than just old CI.

But to not complicate things: what I mean with "observer" above is the entire measurement apparatous. Ie. detector, slits etc. If you change the slits, the measurement devices changes.

Although it's true that there may be also a human observer, but since the human-measurement devices interaction is purely classical (ie reading a gage or a counter or plate) it is "trivial"(ie classical) in the analysis since we can disregard it.

Classical<->classical communication is commutative, and is thus "trivial" at least in this discussion.

/Fredrik

 

[Fredrik]

Instead of the particle also being wave and interfering with itself. You mentioned about "all the paths from the emitter to the detector must be included in the calculation of the total amplitude for detection", so instead of the particle turning into a wave. It literally takes all path and the final interference of the single particle is caused by this?

No. I didn't say that the particle takes all paths, because QM doesn't say that it does. The whole point of saying what I said instead of saying that the particle interferes with itself is to avoid making claims that QM doesn't. I'm just saying that those paths are a part of the calculation of the amplitude for detection. I'm not saying anything about what "actually happens".

If you'd say it is just mathematical. Pls. explain why it could be since an actual particle is emitted.

As I said yesterday in one of these threads, there are only two kinds of answers to questions about reality: Answers given by theories, and BS. I assume that you don't want a BS answer, so I can only explain "why it could be" if there's a theory that provides an answer. Do you know any such theory? I don't.

Unless only measurement make sense because somehow the universe before measurement is in some processing unit in some distant surface boundary courtesy of the Holographic Principle.

If this is not a crackpot interpretation, then you should at least reference an article in a peer-reviewed physics journal that explains it. I can't promise you that I would read it, but I do promise that I won't discuss anything that looks like a crackpot interpretation.

 

[Varon]

No. I didn't say that the particle takes all paths, because QM doesn't say that it does. The whole point of saying what I said instead of saying that the particle interferes with itself is to avoid making claims that QM doesn't. I'm just saying that those paths are a part of the calculation of the amplitude for detection. I'm not saying anything about what "actually happens".

So it's possible that nothing actually happens? And only the calculations make sense? Thinking about particle physics gauge theory and all those symmetries. It's in the math too and nothing Newtonian actually happens. Is this what you are saying that can also happen to our garden variety non-relativistic QM?

As I said yesterday in one of these threads, there are only two kinds of answers to questions about reality: Answers given by theories, and BS. I assume that you don't want a BS answer, so I can only explain "why it could be" if there's a theory that provides an answer. Do you know any such theory? I don't.

Interesting thoughts. Do you have a website or some article or something about this?

If this is not a crackpot interpretation, then you should at least reference an article in a peer-reviewed physics journal that explains it. I can't promise you that I would read it, but I do promise that I won't discuss anything that looks like a crackpot interpretation.

I just read about it in Brian Greene The Hidden Reality although he used the word "Simulation" but I think we must not use the word "simulation" because it denotes "conspiracies" which can only turn off serious scruntiny of the principle. So let's ignore about this simulation thing for now. Our reality now is much more interesting than it.

 

[Fredrik]

So it's possible that nothing actually happens?

I think it's obvious that something happens in an actual experiment, but it's possible that QM can't tell us what that is. In particular, it may not give us an accurate picture of what the system is really doing between state preparation and measurement.

Interesting thoughts. Do you have a website or some article or something about this?

Unfortunately no. These are things I had to figure out on my own, since they're not explained in any of the physics books I've read.

I haven't answered your question in the other thread yet because I need more time to think about it.

 

[Varon]

I think it's obvious that something happens in an actual experiment, but it's possible that QM can't tell us what that is. In particular, it may not give us an accurate picture of what the system is really doing between state preparation and measurement.

That's the purpose why we have all those interpretations.. in order to describe what could be happening between state preparation and measurement. But there is another possibility. That nothing ontologically happens between measurements. That it's only the math that works and it's only outputted in the measurement. This is Aage Bohr extreme Copenhagen Interpretation where only clicks and measurements exist. This is QM in its purest form. But this sounds mind boggling. And if so. Then one entertains the Interpretation which wants to describe what happens between state preparation and measurement. So when you want to propose just pure QM without any extra assumptions, I guess you are holding Aage Bohr view unconsciously.

Unfortunately no. These are things I had to figure out on my own, since they're not explained in any of the physics books I've read.

I haven't answered your question in the other thread yet because I need more time to think about it.

 

[Fredrik]

So when you want to propose just pure QM without any extra assumptions, I guess you are holding Aage Bohr view unconsciously.

Absolutely not.

 

[Varon]

Absolutely not.

I was quite perplexed by your positions until I read a 2009 thread Demystifier shared and finally understood what's on your mind. In the thread you commented on this statement by Demystifier:

"4. Information interpretation - the wave function does not represent reality, but only the information about reality. (It is somewhat similar to 2., but still significantly different from it.)"

You answered:

"If I understand 4 correctly, it's the "interpretation" I've been supporting in a large number of posts here. There are many different ways to say the same thing, for example:

4'. The wavefunction doesn't represent the properties of the physical system. It represents the properties of an ensemble of systems that have been identically prepared.

4''. QM is a set of rules that tell us how to compute the probabilities of possible results of experiments. Nothing more, nothing less. It doesn't include, and doesn't need, an ontological interpretation."

~~~~~~~~~~~~~~~~~~
Fred, you should have mentioned yours is about information interpretation to distinguish from shut up and calculate. The easiest way to understand your point is by analogy of computer progamming. Imagine simulating a world, we have an equation to describe the ensemble of experimental setup. Here the software doesn't describe a single system and hence no ontology for it. Agree?

 

[vanhees71]

It's also known as "minimal statistical interpretation" and is most clearly worked out by Ballentine in his famous RMP article

Ballentine, Leslie E.: The Statistical Interpretation of Quantum Mechanics, Rev. Mod. Phys. 42, APS, 358–381, 1970

or in his textbook

L. Ballentine, Quantum Mechanics, Addison-Wesley

It's my favorite interpretation since it precisely describes what physicists do when applying quantum theory to real-world experiments: They repeat the experiments with identically prepared objects as often as needed to gather "enough statistics". Thus, it's the most realistic interpretation and last but not least contains the least "mumbo jumbo esoterics" as Copenhagen, Princeton, or (the worst of all) Bohm-de Broglie. It's the good old non-nonsense interpretation invented originally by Born.

 

[Varon]

It's also known as "minimal statistical interpretation" and is most clearly worked out by Ballentine in his famous RMP article

Ballentine, Leslie E.: The Statistical Interpretation of Quantum Mechanics, Rev. Mod. Phys. 42, APS, 358–381, 1970

or in his textbook

L. Ballentine, Quantum Mechanics, Addison-Wesley

It's my favorite interpretation since it precisely describes what physicists do when applying quantum theory to real-world experiments: They repeat the experiments with identically prepared objects as often as needed to gather "enough statistics". Thus, it's the most realistic interpretation and last but not least contains the least "mumbo jumbo esoterics" as Copenhagen, Princeton, or (the worst of all) Bohm-de Broglie. It's the good old non-nonsense interpretation invented originally by Born.

But statistical interpretation has one problem with say, one buckyball at a time double slit experiment. Supposed you were the buckyball and you were sent off from the emitter... what would happen to you.. which slits would you pass thru and is there some force pushing you to either slit?

Therefore the software must take into account one particle at a time. How does it model this. This is the question.

 

[Demystifier]

It's also known as "minimal statistical interpretation" and is most clearly worked out by Ballentine in his famous RMP article

Ballentine, Leslie E.: The Statistical Interpretation of Quantum Mechanics, Rev. Mod. Phys. 42, APS, 358–381, 1970

or in his textbook

L. Ballentine, Quantum Mechanics, Addison-Wesley

It's my favorite interpretation since it precisely describes what physicists do when applying quantum theory to real-world experiments: They repeat the experiments with identically prepared objects as often as needed to gather "enough statistics". Thus, it's the most realistic interpretation and last but not least contains the least "mumbo jumbo esoterics" as Copenhagen, Princeton, or (the worst of all) Bohm-de Broglie. It's the good old non-nonsense interpretation invented originally by Born.

So when you see a magic trick, you never try to guess how the performer could possibly do it?

 

[yoda jedi]

You shouldn't take these examples too literally. What collapses a wave function is an interaction with
something.
The "looking" idea is meaningful in that it is necessary to shine a "light" on something to see it.

another object ?



.

 

[nouveau_riche]

i think there is a need of an additional field(i prefer to say it a pattern) that is responsible for creating different wave functions from the universal

i think this experiment would suffice
"suppose an apparatus is set up to observe a single particle but this apparatus allow many observer to do that,now say some 10 observer decide to look for that particle but with different ways like they simultaneously measure particle spin around different axis..

what they finally will observe in terms of state of the particle is the key here"

if we just think observation to b an event then the simultaneous observation will have wave functions overlapped with that of observers

if simultaneous observation is not possible then give the reason for it?

 

[Fredrik]

if simultaneous observation is not possible then give the reason for it?

Simultaneous observability fails when devices designed to prepare the system with well-defined values of the observables interfere with each other. In the case of spin, the state preparation device would include a pair of magnets. If you put two pairs of magnets in the same location, the fields would add up, and you'd end up preparing the system in some state in which neither of the observables you're interested in has a well-defined value.

 

[Brainguy]

I know nothing about decoherence and wave functions collapsing, but let's say the cat exists in a superposition of alive and dead inside the box. If someone killed the cat,and put it in the box does it still exist Alive/dead? The killer knows it's dead, what if the killer dies before telling anyone else about the cat? Can th cat come back to life? I don't think so. But it is a cool idea that if we don't open the box until quantum mechanics can choose where to collapse the cat to, we could open the box with at least a 51% chance of getting an alive cat, mambye even a certain chance! Just lock up a dying person in the freezer and call 911 and when they ask: fire,ambulance or police, tell them: no, I need the mathematician.

 

[lc78]

and how does observing, besides being a point of being and hence, being part of it, change anything? well, in change, as in the the sun's light affecting our weather here, does observing the plasma affecting our weather enlighten anyone to the point of figuring out how streaming lightenergy interacts with ongoing dynamics here? (re:reality exists!) as an observer I can go to soho-nasa and watch the suns' CME's and figure out when to do the rugs so I can hang them out to dry, so does reality mean that rugs drying on the line are an observer? certainly the water inside the rugs are observing the sun's drying actions. personally I subscribe to the isness...we are all one, we are all connected, the water, the sun, the reality and me are observing. Everything is.
perhaps another thought: does being able to see the CME's online make me a front line observer? see, if you go with the isness, then there is no front, no back, no inbetween, the observer, the observed, all one.

 

[schlukhash]

On the other hand, reality exists by being created. The least we can do is observe our environment for seeing created things that are constructed through higher levels of observing. Seemingly infinite states of coherence from the shear drive to adhere. On a level so vast its taking detours from a completed state to statisticly analize its self.

 

[lc78]

Perhaps reality exists by being the creator. there is a vast nothingness that we know nothing of except its there, if we can see it, then its observable but does the nothingness exist? does it adhere? does it not? if in its adherence it causes chaos because of its state, then it doesn't. also the nothingness that we know nothing of (cannot see/grok) and we do not observe it well yet if at all. Remember Marie and Pierre Curie, they were astounded to see their experiments on nothingness shine. And then the level that's vast, the nothingness that we have yet to understand is a part of that. the vastness liking a little diversity; doubtful in this state of being to be able to identify existences that are totally not in our dimensional field, but then our consciousness perhaps being built on by the same forces of being seek a comprehension.

 

[schlukhash]

The truth so simple ittd be boring :)
Although it was to my understanding the "observer photon" is altering the wavefunction of the target particle.

 

[pallidin]

The truth so simple ittd be boring :)
Although it was to my understanding the "observer photon" is altering the wavefunction of the target particle.

Invasive observation(photon towards target) yes.
Passive observation(photon coming from target) no.

 

[skippy1729]

About what your describe above that it's just information of the observer. But there is interaction with the observed. For example. In the absence of measurement to determine its position, the electron has no position. And your information update of the wave function should be more complicated (than what you described) because it is interactive with something that appear only when observed. Incidentally, I read what you described is called the Ignorance Interpretations proposed at Solvay Congress 1927 and debunked by Dirac because of what I just mentioned.

I read (and re-read) the sentences but see no logical argument. Perhaps you could clarify.

Thanks, Skippy

PS If you have a reference to Dirac's argument (preferably original) I would appreciate it.

 

[danR]

Hi,

Reading about quantum mechanics, the probability wave is so that a particle can be everywhere. But when observed, it's probability wave collapses and the particle has to take a definite state.

The example were given for Schrödinger's cat, which is either alive or dead only after we open the box to look at it. Other examples could be that the moon might not exist in the sky if no one look at it. Or a tree falling in the forest is not really falling if no one checks it.

What is the power of the observer to dictate a behavior to a quantum particle? In other words, why would the state of dead/alive of Schrödinger's cat materializes only when I look at it while the cover of the box was actually staring at it the whole time?

In the case of the moon, how come it materializes at the same position while there are billions of different of conscious observers? And on top of that, its position is even predictable.

Thanks for any clarification.

If the modern view of 'observation' has come to involve nothing more sentient than 'any apparatus, system or interaction that necessarily resolves the position or momentum of an electron', then I'd have to say that there is no such thing as an un-oberved electron.

That, even in the middle of inter-galactic-group space, an electron is constantly being locally 'probed'/observed by virtual photons, leptons, and other vacuum-energy junk that is demanding of the electron its spin, charge, position, so that these other particles can make reasonable individual and ensemble adjustments to the presence of the intruder.

And, that a 10 gigabuck apparatus introduced to this space by a sentient, conscious theoretical physicist at the controls is not invested with any special credentials to greater 'observer-status' over those of even a mere virtual positron.

Under these considerations, and speaking only as a layman, I find the CI immaterial, and many-worlds requiring a preposterous multiplication of worlds every Planck-time there is an 'observation' at every Plank-volume. In other words, even though de Broglie/Bohm scheme requires a distasteful introduction of hidden variables, its infraction of conceptual parsimony is less distasteful than an ontological reality bursting unparsimoniously at the seams with universes.

In other words, if there is a Consumer's Reports for the lay science reader, an electron with a real place and energy with an ontologically real wave function, or pilot wave, or whatever, has the fewest x-marks in its feature row over the competition's, even if the only thing going for it is that it has a certain satisfying macroscopic realist quality to it.

And that the cat is definitely, genuinely, really, ontologically dead or alive before we open the box. Totally.

 

[IllyaKuryakin]

Whew! It took most of my afternoon to read this thread and all it's references. This new experimental evidence collected by way of weak measurment Answers many of the questions here.

See: http://www.physorg.com/news/2011-06-quantum-physics-photons-two-slit-interferometer.html

After reading this carefully, I come to the conclusion that we cannot claim that nothing is happening here between emmision of the photon and the reception of it but the statistical math.

Here is a quote: Our measured trajectories are consistent, as Wiseman had predicted, with the realistic but unconventional interpretation of quantum mechanics of such influential thinkers as David Bohm and Louis de Broglie," said Steinberg.

The article continues: The original double-slit experiment played a central role in the early development of quantum mechanics, leading directly to Bohr's formulation of the principle of complementarity. Complementarity states that observing particle-like or wave-like behaviour in the double-slit experiment depends on the type of measurement made: the system cannot behave as both a particle and wave simultaneously. Steinberg's recent experiment suggests this doesn't have to be the case: the system can behave as both.

"By applying a modern measurement technique to the historic double-slit experiment, we were able to observe the average particle trajectories undergoing wave-like interference, which is the first observation of its kind. This result should contribute to the ongoing debate over the various interpretations of quantum theory," said Steinberg. "It shows that long-neglected questions about the different types of measurement possible in quantum mechanics can finally be addressed in the lab, and weak measurements such as the sort we use in this work may prove crucial in studying all sorts of new phenomena.

"But mostly, we are all just thrilled to be able to see, in some sense, what a photon does as it goes through an interferometer, something all of our textbooks and professors had always told us was impossible."

In this poster's opinion, it's unfortunate that a simpler and more conventional result was not found, but the results are undeniable. The "matter probability wave" or whatever you wish to call it, interferes with itself, guiding the particle into the interference pattern location recorded in the classic double slit experiment.

In the end, the Copernican principle holds sway, and the Universe does not exist only because humans are here to observe it. Nor does the entire universe split in two every time a leaf falls face up or face down on the ground.

There are no hidden variables and the ontology is clear. The Universe exists whether we observe it or not. Our difficulty in observing it is a simple matter of the thermodynamics as explained by Luis de Broglie's famous formula Action/h=-entropy/k. You just can't move information from a particle to it's surrounding environment without effecting the entropy of the particle-measurement system.

Whether the wave structure of matter is in fact a standing wave, as proposed by de Borglie, a spherical in and out wave as proposed by Feynman's PHD thesis, or simply a scaler wave as proposed by Wolf, it's becomming more obvious by the second, our insistence on viewing matter as a solid particle has held quantum physics hostage and created almost intractable measurement problems for nearly 80 years.

Now, finally, we seem to be emerging from a very long and very dark tunnel. Quantum wave physics and special relativility can unite in a form like E=hf=mc^2 and we can finally move forward again.

My advice, as distasteful as it may seem, brush up on your French.

Of course, the above just my own humble opinion.

 

[Fyzix]

Uhm...

Yea, you should read this: http://scienceblogs.com/principles/2011/06/watching_photons_interfere_obs.php

 

[IllyaKuryakin]

Uhm...

Yea, you should read this: http://scienceblogs.com/principles/2011/06/watching_photons_interfere_obs.php

Thanks. I read it yesterday. Unfortunately, I believe Chad missed the point of the experiment. The experiment doesn't tell us the exact nature of matter, nor did Stienberg claim he had solved all the riddles of QM. In my own humble opinion however, it is a giant step in the direction of gaining the experimental data necessary to answer all these questions, and it clearly answers two of them. What happens between the emmision of the photon and the detection of it on the other side of the double slit. Does nothing but statistical math occur, or is there a physical process subject to investigation taking place? Statistical math does not leave clearly identifiable trajectory trails. Finally, we have a process to investigate and perhaps Chad would be a bit more excited had he not had such a busy and tireing week.

The second important question that we are obtaining data on had been haunting us for 80 years, how can a single solid particle possibly split into and interfere with itself? In fact, there were never any solid particles. Catch the wave?

Postscript: In a very real sense, Stienberg has shown that not only does the Universe exist even if we don't observe it, it exists even if we can't observe it. Is that worthy of a Nobel Prize? That's not for me to judge, and probably not for Chad either.

 

[Fyzix]

I'm not sure this is what the experiment showed.

From the people conducting the study it definitely seemed like they interpreted it as solid photons.
like deBroglie Bohm imagined.

 

[IllyaKuryakin]

I'm not sure this is what the experiment showed.

From the people conducting the study it definitely seemed like they interpreted it as solid photons.
like deBroglie Bohm imagined.

Well, perhaps something like a spherical in and out wave along the lines of Feynman, or perhaps as Stienberg believes, a particle with a pilot wave, as per de Broglie-Bohm, a good discussion of which is here: http://plato.stanford.edu/entries/qm-bohm/

In any case, once we are able to observe a physical process, we can look for additional experiments to further describe the process. While de Broglie-Bohm may provide the simplest method to describe the measured trajectories, as Prof. Orzel points out, there are other methods that will produce the same result. Most of the time, Occam's Razor is pretty sharp, but not always. Or as Isaac Newton put it, "We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances." The introduction of the pilot wave has always been considered by many as an unnecessary complication. As always, we need more data to discriminate between these competeing theories. And of course, if several theories produce the same end results, are they not just functionally equilivant? I can't answer these questions, but I'm very happy we are creating the measurements that may someday lead us to the answers.

 

[danR]

Well, perhaps something like a spherical in and out wave along the lines of Feynman, or perhaps as Stienberg believes, a particle with a pilot wave, as per de Broglie-Bohm, a good discussion of which is here: http://plato.stanford.edu/entries/qm-bohm/

In any case, once we are able to observe a physical process, we can look for additional experiments to further describe the process. While de Broglie-Bohm may provide the simplest method to describe the measured trajectories, as Prof. Orzel points out, there are other methods that will produce the same result. Most of the time, Occam's Razor is pretty sharp, but not always. Or as Isaac Newton put it, "We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances." The introduction of the pilot wave has always been considered by many as an unnecessary complication. As always, we need more data to discriminate between these competeing theories. And of course, if several theories produce the same end results, are they not just functionally equilivant? I can't answer these questions, but I'm very happy we are creating the measurements that may someday lead us to the answers.

I'm in substantial agreement with your drift. The past 100 years has given us time to reflect on and weigh the relative unparsimonies, 'extraordinary claims', excess moving parts, hidden variables, etc. of all the competing scenarios. The popular scientific press has confused the issue of 'observer' almost to the extent that the public would think a new universe only occurs when a scientist fires up his spin-measurer and gets a result. That would seem parsimonious enough, even if as many as 1,000 new worlds/year, and Gedanknenexperimentkatzen tot und leben, are generated thereby. Most street people, and all scientists can live with that; and science-fiction writers can live by that. It makes for good pot-boilers.

But the reasonable person would balk when the real number of universes bids fair to challenge the lower limits of Cantor's 'terrible dynasties'.

And I think it's a reasonable analogy that, as Gödel showed there exists unprovable truths in the body of number theory, and cosmological theorists entertain metaphysical notions to serve as 'physics' in lieu of testable 'before the BB' theories, we need only posit a few unfalsifiable arrangements for quantum entities. The alternatives are simply more distasteful.

 

[IllyaKuryakin]

I'm in substantial agreement with your drift. The past 100 years has given us time to reflect on and weigh the relative unparsimonies, 'extraordinary claims', excess moving parts, hidden variables, etc. of all the competing scenarios. The popular scientific press has confused the issue of 'observer' almost to the extent that the public would think a new universe only occurs when a scientist fires up his spin-measurer and gets a result. That would seem parsimonious enough, even if as many as 1,000 new worlds/year, and Gedanknenexperimentkatzen tot und leben, are generated thereby. Most street people, and all scientists can live with that; and science-fiction writers can live by that. It makes for good pot-boilers.

But the reasonable person would balk when the real number of universes bids fair to challenge the lower limits of Cantor's 'terrible dynasties'.

And I think it's a reasonable analogy that, as Gödel showed there exists unprovable truths in the body of number theory, and cosmological theorists entertain metaphysical notions to serve as 'physics' in lieu of testable 'before the BB' theories, we need only posit a few unfalsifiable arrangements for quantum entities. The alternatives are simply more distasteful.

Well, to my understanding, Bohmian Mechanics has never been falsified. It appears John Bell thought it was valid:

(Bell 1987, p. 160):

"But in 1952 I saw the impossible done. It was in papers by David Bohm. Bohm showed explicitly how parameters could indeed be introduced, into nonrelativistic wave mechanics, with the help of which the indeterministic description could be transformed into a deterministic one. More importantly, in my opinion, the subjectivity of the orthodox version, the necessary reference to the ‘observer,’ could be eliminated. ...
But why then had Born not told me of this ‘pilot wave’? If only to point out what was wrong with it? Why did von Neumann not consider it? More extraordinarily, why did people go on producing ‘‘impossibility’’ proofs, after 1952, and as recently as 1978? ... Why is the pilot wave picture ignored in textbooks? Should it not be taught, not as the only way, but as an antidote to the prevailing complacency? To show us that vagueness, subjectivity, and indeterminism, are not forced on us by experimental facts, but by deliberate theoretical choice?"

In my own humble opinion, I believe that until these latest experimental results came out, the "pilot wave" was considered a falsified crackpot theory. Now we have the opportunity to revisit this piece of work in light of experimental trajectory data almost perfectly agreeing with Bohmian Mechanics. I expect lots of pushback from those who have devoted their lives to statistical QM, but if de Broglie-Bohm is valid, the truth has a way of eventually coming to light. This method of weak measurement is very new, having only developed over the last 5 years or so. Considering we've waited for about 80 years for someone, anyone, to shed some light on this measurement problem, I'd counsel keeping an open mind until this all plays out. It's very unfortunate that new theories are immediately labeled as "crackpot" and attacked from all sides in this community of physics (not so much in this particular forum though, which is why I like it).

Remember that Einstein had a terrible time gaining acceptance of GR. It's a natural thing. The vast majority of new theories that come out are, at least in part, incorrect. So if one attacks every new theory, they will be right most of the time. I'm trying to keep an open mind, within the constraints of experimental evidence. Theories can be incorrect, and falsifications of those theories can be incorrect, as was proved many times during the course of intense challenges to GR by some of the greatest minds of the time. Experimental results can be misinterpreted, but I sense there is something here worth further investigation. I look forward to the future of this course of research.