Macro Superposition: Does Size Matter?

In summary, the conversation discussed the concept of superposition in macro and micro objects. It was mentioned that as objects get bigger, it becomes more difficult to maintain coherence over space and time, making it harder to detect quantum effects. However, the double slit experiment with photons and electrons showed interference patterns without isolating the particles from the external environment. This led to confusion and a question about whether the double slit experiment is the only example of superposition in the macro world without isolating particles, and if there are other examples. It was also mentioned that while decoherence plays a role in larger objects, it has less effect on single free electrons.
  • #36
batmanandjoker said:
bhobba kept using the word entangled but I think he meant interaction is this correct this is what confused me.

When particles interact that may become entangled or not - but interaction is required for entanglement - that, and if they are created that way to begin with, really are the only ways for them to be entangled:
http://en.wikipedia.org/wiki/Quantum_entanglement

Thanks
Bill
 
Physics news on Phys.org
  • #37
batmanandjoker said:
So it is the interaction with the external enviorment that collapses particles superposition in the macro world,

Correct, it’s the interaction with the environment that disturbs the “macroscopic superposition” to collapse/decohere. Here’s an article on the fattest Schrödinger cats realized to date, an experiment performed on large organic molecules consisting of 430 atoms, in a coherent state where the matter waves are all in step. Here’s the experiment.

... I’ve always wonder what it takes to get an elephant (not in the room, but) in a coherent state ... :smile:

batmanandjoker said:
does entanglement (which I do know what it is) have anything to do with this collapse or was I just using the incorrect termonolgie.

Yes, that could be the case, but I can’t say if that’s the case in all situations. I leave that to the professional experts in this thread.

(If I don’t remember wrong, Roger Penrose has stated that the whole universe is/will be entangled?? And if this is correct, entanglement always causes collapse/decoherence... but I’m not sure...)
 
  • #38
From what I understand decoherance causes particles to collapse IE remove their state of superposition is this correct
 
Last edited:
  • #39
batmanandjoker said:
From what I understand decoherance causes particles to collapse IE remove their state of superposition is this correct

It causes APPARENT collapse.

I will leave it up to you to investigate the difference.

Thanks
Bill
 
  • #40
I really need help here what do you mean by APPARENT collapse can you be specific are you suggesting your not exactly sure that decoherence collapses wave functions IE superposition. Because this is contradicatry to your earlier posts. This is very confusing for me I don't even know where to begin INVESTIGATING whatever diffrence your talking about. Does decoherance cause wave function collapse or create the illusion that it does and everything is still in superposition. Any help would be greatly appreciated.
 
  • #41
batmanandjoker said:
This is true but how do you explain this

http://www.nature.com/news/2010/100317/full/news.2010.130.html

they detected superposition in a macro object could you please explain your perspective on this article. Thanks.
The experiment just demonstrates that QM is also a macroscopic phenomenon; that is, QM does not only apply at the micro level. While there is a superposition of states that is not the same thing as observation of an object at 2 places at once.
 
  • #42
Maui said:
No. The double slit experiment has been carried out without isolating single electrons from their 'environment'(whatever that means quantum mechanically!) or isolating them from interacting with the slits(electrons somehow do not seem to care about interaction with the plate that houses the slits so no decoherence there).

http://physicsworld.com/cws/article/news/2013/mar/14/feynmans-double-slit-experiment-gets-a-makeoverBTW, if you want a real understanding of what is going on, a 'bare' decoherence theory will only get you half-way at most.
I feel that this is a false statement nowwhere in the article does it state that the electrons were not isolated from their enviorment it has already been refrenced by a sci advisor that electrons need to be in a vacuum to exhibit superposition. Can a sci advisor tell me if I am correct.
 
Last edited:
  • #43
bohm2 said:
The experiment just demonstrates that QM is also a macroscopic phenomenon; that is, QM does not only apply at the micro level. While there is a superposition of states that is not the same thing as observation of an object at 2 places at once.
have to be seen at at 1010 - 10 20 atoms.
 
  • #44
batmanandjoker said:
I really need help here what do you mean by APPARENT collapse can you be specific are you suggesting your not exactly sure that decoherence collapses wave functions IE superposition. Because this is contradicatry to your earlier posts. This is very confusing for me I don't even know where to begin INVESTIGATING whatever diffrence your talking about. Does decoherance cause wave function collapse or create the illusion that it does and everything is still in superposition. Any help would be greatly appreciated.

Apparent means observationaly its the same - but actual collapse is another matter.

The jig is up here - can't give any more detail without the math - it requires knowledge of the difference between proper and improper mixtures which requires considerably more background than you have. Here is the detail for future reference:
http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf

Thanks
Bill
 
  • #45
batmanandjoker said:
I feel that this is a false statement nowwhere in the article does it state that the electrons were not isolated from their enviorment it has already been refrenced by a sci advisor that electrons need to be in a vacuum to exhibit superposition. Can a sci advisor tell me if I am correct.


I could be wrong about the vacuum but for different reasons not related to decoherence. The distances between the slits are extremely tight and you need electrons that travel unimpeded from the electron gun to the screen. That is why you want to remove the air so that a near perfect straight line is traversed.

As I said earlier, if environmentally induced decoherence had anything to do with the behavior in the double slit experiement, electrons would have decohered and collapsed upon interaction with the slits and interference would not have been observed. But it is. The above approach treats objects as if there were different levels of quantumness - classical quantumness not exlpained by quantum mechanics and regualr quantumness that is thoroughly explained by it. However accepting the premise leads to the conclusion that the slits must be made of that special classical quantumness and should therefore cause decoherence to the passing electrons at all times.

Btw you should not read these interpretational opinions like Gospel. There are quite a number of possible explanations and as of today no one knows which is right(not even the sci advisors ;) )
 
Last edited:
  • #46
Maui said:
I could be wrong about the vacuum but for different reasons not related to decoherence. The distances between the slits are extremely tight and you need electrons that travel unimpeded from the electron gun to the screen. That is why you want to remove the air so that a near perfect straight line is traversed.

As I said earlier, if decoherence had anything to do with the behavior in the double slit experiement, electrons would have decohered and collapsed upon interaction with the slits and interference would not have been observed. But it is. The above approach treats objects as if there were different levels of quantumness - classical quantumness not exlpained by quantum mechanics and regualr quantumness that is thoroughly explained by it. However accepting the premise leads to the conclusion that the slits must be made of that special classical quantumness and should therefore cause decoherence to the passing electrons at all times.

Btw you should not read these interpretational opinions like Gospel. These are quite a number of possible explanations and as of today no one knows which is right(not even the sci advisors ;) )
Between a sci advisor and some random poster sorry but I prefer to listen to a sci advisor for all I know you might be one of those quantum spiritual types.

Anyways please please in lamen terms if you can distinguish or TRY to explain the diffrence between an observational collapse and an actual or mathematical collapse if that's what your implying. Can one mathematiclly determine collapse while at the same time observe collapse experimentally. Please you would help me a great deal see I suffer from obsessive compulsive disorder and the distortion of reality in my own mind created by my own ignorance of how some suggest the quantum world contradicts the macro classical world creates anxiety for me.

THE BASIC QUESTION IN YOUR OPINION CAN ONE THING BE IN TWO PLACES AT THE SAME TIME IN THE MACRO WORLD WITHOUT REMOVING THE EXTERNAL REALITY, PHOTONS BEING THE EXEPTION. I KNOW YOU ALREADY ANSWERED THIS IN YOUR PREVIOUS POSTS BUT NOW I FEEL YOUR TELLING ME THAT WITHOUT MATHEMATICAL CERTIANTY ABSOLUTE COLLAPSE CANT BE DETERMINED. CAN THE MATH HOWEVER BE IN SYNCRONICITY WITH THE OBSERVATIONAL RESULTS. I AM SO CONFUSED AND VERY BUYS IN MY LIFE RIGHT NOW THAT I DONT HAVE THE TIME (HOURS OR WHOLE DAY) TO GO THROUGH COMPLEX DOCUMENTS IN QM. PLEASE HELP ME THE BEST YOU CAN ANY OF THE SCI ADVISORS.

SORRY FOR ALL CAPS AND SPELLING IM USING AN ITALIAN COMPUTER THAT DOESENT HAVE SPELL CHECK.
 
Last edited:
  • #47
In post 13 you asked what happens in the double slit experiment between observations - i.e. you asked for opinions and you received opinions. QM does not describe what happens between observations so you should not protest that you only get opinions. A far better approach would have been to first familiarize yourself with the basic concepts and make up your own mind instead of taking someone's word for it on faith. I was honest with you in not selling you an "explanation" but that somehow got lost on you and the badges.
 
  • #48
This thread is getting to be too popular. That means it will be closed soon.

(just joking...)
 
  • #51
batmanandjoker said:
I really need help here what do you mean by APPARENT collapse can you be specific are you suggesting your not exactly sure that decoherence collapses wave functions IE superposition. Because this is contradicatry to your earlier posts. This is very confusing for me I don't even know where to begin INVESTIGATING whatever diffrence your talking about. Does decoherance cause wave function collapse or create the illusion that it does and everything is still in superposition. Any help would be greatly appreciated.

bhobba said:
Apparent means observationaly its the same - but actual collapse is another matter.

The jig is up here - can't give any more detail without the math - it requires knowledge of the difference between proper and improper mixtures which requires considerably more background than you have. Here is the detail for future reference:
http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf

Thanks
Bill

I too have had a very hard time too understanding what bhobba means by apparent collapse. In my understanding, from the link he provided, it is the same as collapse. http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf (p38): "Ignorance interpretation: The mixed states we find by taking the partial trace over the environment can be interpreted as a proper mixture. Note that this is essentially a collapse postulate."
 
  • #52
atyy said:
I too have had a very hard time too understanding what bhobba means by apparent collapse. In my understanding, from the link he provided, it is the same as collapse. http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf (p38): "Ignorance interpretation: The mixed states we find by taking the partial trace over the environment can be interpreted as a proper mixture. Note that this is essentially a collapse postulate."

I think that all that is meant by "apparent collapse" is that one can use mixtures instead of superpositions to compute expectation values. The use of mixtures is consistent with the claim that the wave function has collapsed into some definite state (but it's unknown which one), but it doesn't actually imply it.
 
  • #53
stevendaryl said:
I think that all that is meant by "apparent collapse" is that one can use mixtures instead of superpositions to compute expectation values. The use of mixtures is consistent with the claim that the wave function has collapsed into some definite state (but it's unknown which one), but it doesn't actually imply it.

I'm not sure I understand correctly, but it seems to me that there are two things that require a proper mixture:
1) filtering measurements, used for state preparation
2) unitary evolution of the mixture after the measurement

The reduced density matrix produces an improper mixture. If one uses the post-measurement mixture for state preparation or evolves it unitarily, then the transition from an improper to a proper mixture is collapse.
 
  • #54
batmanandjoker said:
Between a sci advisor and some random poster sorry but I prefer to listen to a sci advisor for all I know you might be one of those quantum spiritual types.

good joke !

Beware !

beware of apodictical parrots.


.
 
  • #55
batmanandjoker said:
Between a sci advisor and some random poster sorry but I prefer to listen to a sci advisor for all I know you might be one of those quantum spiritual types.

Anyways please please in lamen terms if you can distinguish or TRY to explain the diffrence between an observational collapse and an actual or mathematical collapse if that's what your implying. Can one mathematiclly determine collapse while at the same time observe collapse experimentally. Please you would help me a great deal see I suffer from obsessive compulsive disorder and the distortion of reality in my own mind created by my own ignorance of how some suggest the quantum world contradicts the macro classical world creates anxiety for me.

THE BASIC QUESTION IN YOUR OPINION CAN ONE THING BE IN TWO PLACES AT THE SAME TIME IN THE MACRO WORLD WITHOUT REMOVING THE EXTERNAL REALITY, PHOTONS BEING THE EXEPTION. I KNOW YOU ALREADY ANSWERED THIS IN YOUR PREVIOUS POSTS BUT NOW I FEEL YOUR TELLING ME THAT WITHOUT MATHEMATICAL CERTIANTY ABSOLUTE COLLAPSE CANT BE DETERMINED. CAN THE MATH HOWEVER BE IN SYNCRONICITY WITH THE OBSERVATIONAL RESULTS. I AM SO CONFUSED AND VERY BUYS IN MY LIFE RIGHT NOW THAT I DONT HAVE THE TIME (HOURS OR WHOLE DAY) TO GO THROUGH COMPLEX DOCUMENTS IN QM. PLEASE HELP ME THE BEST YOU CAN ANY OF THE SCI ADVISORS.

SORRY FOR ALL CAPS AND SPELLING IM USING AN ITALIAN COMPUTER THAT DOESENT HAVE SPELL CHECK.

what is macroscopic for you ?

objects of
1000 atoms
10000 atoms

100 nm or 1000 nm

macroscopic is beyond 10 15 atoms.

the actual experimental limit is 430 atoms.-------
1.-Mass (in grams) equal to the atomic weight (in amu) is called a molar mass.
2.-The collection of atoms in one molar mass is called a mole.
3.-The exact number of atoms in one mole is Avogadro’s number.

Avogadro number
6.022 x 1023.
 
Last edited:
  • #56
atyy said:
I'm not sure I understand correctly, but it seems to me that there are two things that require a proper mixture:
1) filtering measurements, used for state preparation
2) unitary evolution of the mixture after the measurement

The reduced density matrix produces an improper mixture. If one uses the post-measurement mixture for state preparation or evolves it unitarily, then the transition from an improper to a proper mixture is collapse.

The miracle of decoherence is that for all practical purposes, there is no difference between using the post-measurement mixture and using a pure state. The only difference is interference terms that are undetectable in practice.
 
  • #57
What is the diffrence between pure and mixed states in lamen terms I reasearched it but I am not exactly sure I understood the concept and how it applies to how the enviorment (decoherance) collapses particles.

Also if someone could explain the density matrix and how it applies to all this it would be much appreciated.
 
  • #58
batmanandjoker said:
What is the diffrence between pure and mixed states in lamen terms I reasearched it but I am not exactly sure I understood the concept and how it applies to how the enviorment (decoherance) collapses particles.

Also if someone could explain the density matrix and how it applies to all this it would be much appreciated.

If a system is in a pure state, and you know what the pure state is, then your knowledge of the system is complete, and all uncertainty is quantum. If we take a state to apply to an ensemble, this means that every member of the ensemble has been identically prepared and is in the same state.

A proper mixed state means that you do not know exactly what the quantum state is, but only what the state is with some probability, so uncertainty is due to intrinsic quantum uncertainty, as well as your ignorance of the state. In an ensemble, this means that not all members of the ensemble have been identically prepared.

An improper mixed state comes about when the entire system is in a pure state, but you restrict yourself to observing a subsystem. The improper mixed state describes the behaviour of the subsystem.

The density matrix is a way of writing the quantum state so that pure states, proper and improper mixed states can be described in the same mathematical language.

As I understand, decoherence does not collapse the state. In order to have a definite outcome, one must postulate collapse (or use Bohmian or many-worlds formulations). I believe this is also what is said in bhobba's link to Bas Hensen's essay http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf concerning the "Ignorance interpretation" where one postulates "The mixed states we find by taking the partial trace over the environment can be interpreted as a proper mixture. Note that this is essentially a collapse postulate." (p39). For decoherence to give definite outcomes (see Table 3.1 on p39, where "D. Interactions with the environment explain the apparent definiteness of measurement outcomes." needs all 4 assumptions, including assumption 4 that an improper mixture can be interpreted as a proper mixture.

Decoherence does not explain collapse. Decoherence solves the "preferred basis" or "pointer basis" problem. In particular, decoherence says that position is a usually a very good pointer basis, because interactions are usually local in space. From Hensen's p17: "Summarising, the point is that the basis with respect to which decoherence takes place - i.e. superpositions of eigenstates of this basis decohere into a improper mixture of these eigenstates - is determined by the form of the system/apparatusenvironment interaction Hamiltonian. Therefore the'classical' observables, the ones that we perceive as classical, are exactly those determined by this basis. One of the consequences of this is that any interaction described by a potential V(r), is diagonal in position, and therefore position is always the pointer observable measured by the interaction. many interactions in nature are described by such a potential V (R)." See also sections 2.4 and 3.4 of Bas Hensen's essay.
 
Last edited:
  • #59
stevendaryl said:
I think that all that is meant by "apparent collapse" is that one can use mixtures instead of superpositions to compute expectation values. The use of mixtures is consistent with the claim that the wave function has collapsed into some definite state (but it's unknown which one), but it doesn't actually imply it.

Apparent collapse is simple. Technically its that an improper mixed state is observationally indistinguishable from a proper one. If it was a proper one then actual collapse would have occurred.

This has been discussed innumerable times by me and others so I do not know why there is any confusion.

Thanks
Bill
 
  • #60
atyy said:
As I understand, decoherence does not collapse the state.

It transforms a superposition to an improper mixed state - see section 1.2.3 of the paper I constantly post about it:
http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf

When one applies the measurement postulate (ie Born's rule) to an improper mixed state you get exactly the same result as if it was a proper one. There is zero, no way, nada, of observationally telling if it was not a proper one instead. If it was a proper one collapse would have actually occurred because a proper one is a specific state randomly presented for observation.

That is what is meant by apparent collapse. That is what is meant by solving the measurement problem FAPP.

The paper I link to gives a fair and balanced view of the issue - but I personally think the language it uses in saying it doesn't touch the central issue is too pessimistic. Its true - but so? If solves it FAPP.

Thanks
Bill
 
Last edited:
  • #61
batmanandjoker said:
What is the diffrence between pure and mixed states in lamen terms I reasearched it but I am not exactly sure I understood the concept and how it applies to how the enviorment (decoherance) collapses particles. Also if someone could explain the density matrix and how it applies to all this it would be much appreciated.

As mentioned previously on these issues the jig is up. It can't be explained in layman's terms - at least I have no idea how to do it. Its fully explained in the paper I linked to - in particular section 1.2.3 explains exactly the difference between an improper and a mixed state.

You simply need to accept that decoherence, FAPP, results in collapse. If you want to delve deeper you need to learn the technicalities - sorry no out. For example even the term density matrix requires knowledge of what a matrix is which is the subject of college level courses in linear algebra - and that's just one aspect. A layman's explanation is not possible of stuff at that level IMHO. But if anyone wants to have a go then I salute you and hope you succeed. Its beyond me.

Thanks
Bill
 
Last edited:
  • #62
batmanandjoker said:
Anyways please please in lamen terms if you can distinguish or TRY to explain the diffrence between an observational collapse and an actual or mathematical collapse if that's what your implying. Can one mathematiclly determine collapse while at the same time observe collapse experimentally. Please you would help me a great deal see I suffer from obsessive compulsive disorder and the distortion of reality in my own mind created by my own ignorance of how some suggest the quantum world contradicts the macro classical world creates anxiety for me.

THE BASIC QUESTION IN YOUR OPINION CAN ONE THING BE IN TWO PLACES AT THE SAME TIME IN THE MACRO WORLD WITHOUT REMOVING THE EXTERNAL REALITY, PHOTONS BEING THE EXEPTION. I KNOW YOU ALREADY ANSWERED THIS IN YOUR PREVIOUS POSTS BUT NOW I FEEL YOUR TELLING ME THAT WITHOUT MATHEMATICAL CERTIANTY ABSOLUTE COLLAPSE CANT BE DETERMINED. CAN THE MATH HOWEVER BE IN SYNCRONICITY WITH THE OBSERVATIONAL RESULTS. I AM SO CONFUSED AND VERY BUYS IN MY LIFE RIGHT NOW THAT I DONT HAVE THE TIME (HOURS OR WHOLE DAY) TO GO THROUGH COMPLEX DOCUMENTS IN QM. PLEASE HELP ME THE BEST YOU CAN ANY OF THE SCI ADVISORS.

Take a deep breath batman – and relax – you don't have to worry. Our macroscopic everyday world will continue to work as it always has, with or without mathematical equations.

Science is not religion; it will never give you the final, ultimate, and undisputable TRUTH about the world we live in. Science is about making best possible models on how nature works, to be able to make the best possible predictions about what nature will do next. That's all.

QM makes extremely precise predictions about nature, in fact the best we have, but in the light of history, it will (most probably) not be the final scientific model for the microscopic world.

You can think of it like this; imagine there was a guy in 1687 who got his hands on Newton's personal copy of Philosophiæ Naturalis Principia Mathematica and read about Newton's law of universal gravitation, and went completely nuts: What!? A mysterious force, with infinite speed, that affects the entire world!? HELP! The world will collapse!

Not that smart, huh?

Newton was a genius, but he – as everybody else – was limited by the time he lived in. His model still works, in most situations, but Einstein expanded the model to get better and more precise predictions, and by this Einstein also "saved us" (:smile:) from becoming a dreadful black hole, that worried the "fictive guy" back in 1687.

Get it? Don't worry!

It's extremely hard to get large objects in that delicate state of coherence, and when we do, it only last for a very short time. And for living organisms (and their thoughts) I stick out my nose and say – impossible – i.e. without killing the organism in the process.

Finally, a statement from one of the brightest in the development of QM:

"I think I can safely say that nobody understands quantum mechanics." – Richard Feynman​

... and maybe the Measurement problem (wavefunction collapse) is the greatest contributor to this "perplexity" ...
 
  • #63
bhobba said:
That is what is meant by solving the measurement problem FAPP.

Maybe I’m missing something here, are you saying that the measurement problem is solved? :bugeye:

Who got the Nobel Prize for this?
 
  • #64
bhobba said:
Apparent collapse is simple. Technically its that an improper mixed state is observationally indistinguishable from a proper one. If it was a proper one then actual collapse would have occurred.

This has been discussed innumerable times by me and others so I do not know why there is any confusion.

Not everyone reads every post.
 
  • #65
bhobba said:
It transforms a superposition to an improper mixed state - see section 1.2.3 of the paper I constantly post about it:
http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf

When one applies the measurement postulate (ie Born's rule) to an improper mixed state you get exactly the same result as if it was a proper one. There is zero, no way, nada, of observationally telling if it was not a proper one instead. If it was a proper one collapse would have actually occurred because a proper one is a specific state randomly presented for observation.

That is what is meant by apparent collapse. That is what is meant by solving the measurement problem FAPP.

The paper I link to gives a fair and balanced view of the issue - but I personally think the language it uses in saying it doesn't touch the central issue is too pessimistic. Its true - but so? If solves it FAPP.

Thanks
Bill

I agree with the paper you post. What I don't understand is whether in the "Ignorance interpretation" there is any difference between collapse and apparent collapse. Bas Hensen writes http://philsci-archive.pitt.edu/5439/1/Decoherence_Essay_arXiv_version.pdf (p37), assumption 4: "Ignorance interpretation: The mixed states we find by taking the partial trace over the environment can be interpreted as a proper mixture. Note that this is essentially a collapse postulate." In Table 3.1 on p38, Hensen lists the 4th assumption as necessary to give definite outcomes.

There is a similar comment in Schlosshauer's http://arxiv.org/abs/quant-ph/0312059 (p9) "The reduced density matrix looks like a mixed state density matrix because, if one actually measured an observable of the system, one would expect to get a definite outcome with a certain probability; in terms of measurement statistics, this is equivalent to the situation in which the system is in one of the states from the set of possible outcomes from the beginning, that is, before the measurement. As Pessoa (1998, p. 432) puts it, "taking a partial trace amounts to the statistical version of the projection postulate.""

So it would seem that in the "Ignorance interpretation" apparent collapse is collapse. (Or are you not using the "Ignorance interpretation"?)
 
Last edited:
  • #66
atyy said:
"Ignorance interpretation"

Well, if ignorance is the rigorous solution to the measurement problem, Steven Weinberg's words (2005) still holds:

Steven Weinberg said:
Bohr’s version of quantum mechanics was deeply flawed, but not for the reason Einstein thought. The Copenhagen interpretation describes what happens when an observer makes a measurement, but the observer and the act of measurement are themselves treated classically. This is surely wrong: Physicists and their apparatus must be governed by the same quantum mechanical rules that govern everything else in the universe. But these rules are expressed in terms of a wavefunction (or, more precisely, a state vector) that evolves in a perfectly deterministic way. So where do the probabilistic rules of the Copenhagen interpretation come from?

Considerable progress has been made in recent years toward the resolution of the problem, which I cannot go into here. It is enough to say that neither Bohr nor Einstein had focused on the real problem with quantum mechanics. The Copenhagen rules clearly work, so they have to be accepted. But this leaves the task of explaining them by applying the deterministic equation for the evolution of the wavefunction, the Schrödinger equation, to observers and their apparatus. The difficulty is not that quantum mechanics is probabilistic — that is something we apparently just have to live with. The real difficulty is that it is also deterministic, or more precisely, that it combines a probabilistic interpretation with deterministic dynamics.
= unsolved


Guys, before you drive batman nuts, wouldn’t it be fair to explain the difference between interpretations and a theory, empirically verified?
 
  • #67
DevilsAvocado said:
Maybe I’m missing something here, are you saying that the measurement problem is solved? :bugeye:

Who got the Nobel Prize for this?

FAPP - For All Practical Purposes ie APPARENT collapse.

The issue, as has been gone over countess times is, is APPARENT collapse good enough. That is the key, that is the crux.

I have specifically stated many times until I am blue in the face, it does NOT solve the measurement problem - just FAPP. Specific extra interpretive assumptions are required for that. I use the assumption of the ignorance ensemble interpretation, others MW, others decoherent histories. There are tons about - take your pick - its a smorgasbord.

Thanks
Bill
 
Last edited:
  • #68
atyy said:
So it would seem that in the "Ignorance interpretation" apparent collapse is collapse. (Or are you not using the "Ignorance interpretation"?)

I hold to the ignorance interpretation but that is not the issue here.

The issue is what decoherehnce does. Its in any interpretation because it follows from the formalism. Decoherence transforms a superposition into an improper mixed state that is observationally indistinguishable from a proper one. If it was a proper one measurement problem solved - collapse has occurred. But its not. But since its observationally indistinguishable from it, it gives the APPEARANCE of collapse that many such as myself say is good enough - or FAPP solves it.

I, on top of that, make an interpretive assumption in my interpretation, the ignorance interpretation, that what an observation does is select from a conceptual ensemble of outcomes that are there prior to observation. In other words I assume it is a proper mixed state and collapse has occurred . You can do this because its observationally indistinguishable so no inconsistency can arise. It is an assumption of my interpretation not implied by the formalism, like the assumption in Many Worlds that each of the outcomes in the mixed state is a world, like the use of histories in decoherent histories, etc etc.

Thanks
Bill
 
  • #69
Closed for moderation.

EDIT: this thread will remain closed. Everyone has had a chance to say their piece and now the conversation is just going in circles.
 
Last edited:

Similar threads

What is the radius of a superposition
Replies
12
Views
2K
B Are Quantum Entities in Macro Sized Objects Entangled?
Replies
22
Views
2K
I Why no plane waves of macroscopic bodies? The micro-macro threshold...
2
Replies
41
Views
4K
Is the Quantum/Classical Boundary the most important question in Physics?
4
Replies
135
Views
10K
A Spacetime Engineering by Superposition of GWs: Feasible in Theory?
Replies
2
Views
2K
I Why do waves need to match object size for interaction?
Replies
9
Views
2K
Does a black hole have a surface area?
Replies
5
Views
2K
I Why does the amplitude of an undamped driven oscillator not vary with time?
Replies
3
Views
2K
I Does the Amplitude of an Undamped Driven Oscillator Stay Constant Over Time?
Replies
3
Views
2K
I Explore Homogeneity of Space: Effects on Relativity Theory
Replies
1
Views
1K

Hot Threads

Recent Insights

Back
Top