Reality exists when observed, but who is the observer?

[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.

 

[danR]

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.
.
.
.

I've just posted a new question on Bohm and Quantum Computing as an imminently practical test of de Broglie/Bohm. It seems to me that if they actually made a working QC, Bohm would be spectacularly falsified. QC's presuppose the Copenhagen interpretation. I've been harbouring for many years the suspicion that they will never actually produce a QC because it requires for it's ability to solve otherwise theoretically intractable problems, an underlying superposition of all states condition that actually doesn't exist.

 

[IllyaKuryakin]

I've just posted a new question on Bohm and Quantum Computing as an imminently practical test of de Broglie/Bohm. It seems to me that if they actually made a working QC, Bohm would be spectacularly falsified. QC's presuppose the Copenhagen interpretation. I've been harbouring for many years the suspicion that they will never actually produce a QC because it requires for it's ability to solve otherwise theoretically intractable problems, an underlying superposition of all states condition that actually doesn't exist.

I hope someone else has posted a better answer to your question by now, because mine is still very conditional. If a quantum computer works under statistical Quantum Mechanics, then it must also work under the Bohmian Mechanics for Bohmian Mechanics to be valid. My understanding at this point is that Bohmian mechanics reproduces all the same non-local phenomena as statistical Quantum Mechanics. If someone has a better answer, I hope they will share.