Electrons travel faster than the speed of light

[epkid08]

Is it literally possible for them to be in two places at once?
Is this proven; How is this possible?

I mean, sure they travel very, very fast. Even if they travel faster than the speed of light, it would appear so that they are, but nothing can travel at a speed that literally freezes time [only apparently].

I think this hints more towards electrons traveling though another spatial dimension than traveling though time.

 

[Mr Noblet]

An electron is described by its wave function. The wave function is used to find the probability density of the electron, that is, the probability of it being at locations within a certain space. This is because an electron is not a point in the classical sense. It doesn't have an exact location, but a probability density. This can explain why it can be in two places at once. This means that the speed the electron must travel to be in these two locations irrelevant.

 

[Crosson]

Is it literally possible for them to be in two places at once?

No, that is a misconceived term that originates with the sensationalism in the newspapers of the 1930s.

 

[ZapperZ]

No, that is a misconceived term that originates with the sensationalism in the newspapers of the 1930s.

That is not exactly true. The "standard" interpretation for a quantum superposition is that the system has ALL of the states within that superposition before it is measured. This is the common view that has been described in QM (see Phillip Ball's article in May 1st 2008 issue of Nature).

To understand what the quantum–classical transition really means, consider that our familiar, classical world is an ‘either/or’ kind of place. A compass needle, say, can’t point both north and south at the same time. The quantum world, by contrast, is ‘both/and’: a magnetic atom, say, has no trouble at all pointing both directions at once. The same is true for other properties such as energy, location or speed; generally speaking, they can take on a range of values simultaneously, so that all you can say is that this value has that probability. When that is the case, physicists say that a quantum object is in a ‘superposition’ of states.

Thus, one of the key questions in understanding the quantum–classical transition is what happens to the superpositions as you go up that atoms-to-apples scale? Exactly when and how does ‘both/and’ become ‘either/or’?

An electron occupying several locations at once is what the wavefunction is describing in, for example, an H2 molecule, resulting in the bonding-antibonding state. Such a description is consistent with what is being interpreted in all of the Schrodinger Cat-type experiments (i.e. the Delft/Stony Brook SQUIDs experiment where they specifically describe the supercurrent flowing in both directions simultaneously).

So no, this isn't a "... sensationalism in the newspapers of the 1930s..."

Zz.

 

[epkid08]

No, that is a misconceived term that originates with the sensationalism in the newspapers of the 1930s.

Yes.

...and I'm aware of the Uncertainty principle, but just because its location is in a designated area, specifically unknown, doesn't mean it's in all places at the same time in that area.

 

[Ciokko]

have you read the other replies?

 

[Crosson]

The "standard" interpretation for a quantum superposition is that the system has ALL of the states within that superposition before it is measured.

What do you mean in terms of the formalism, 'has all the states'? The state of the system is that superposition, its state is not equal to any of the individual states.

I looked at the Philip Ball decoherence article, and I have studied Josephson junctions and SQUIDS, but I do not interpret quantum mechanics the way you do; it doesn't make sense.

 

[ZapperZ]

What do you mean in terms of the formalism, 'has all the states'? The state of the system is that superposition, its state is not equal to any of the individual states.

The superposition of states where all the orthorgonal states are present in the description of the system has always been interpreted as having those states simultaneously. That's the "paradox" of the schrodinger cat system.

I looked at the Philip Ball decoherence article, and I have studied Josephson junctions and SQUIDS, but I do not interpret quantum mechanics the way you do; it doesn't make sense.

It is not my interpretation. I'm giving the prevailing view of what has been written as the description of superposition. If you look at all the papers, including the Leggett paper that I've mentioned several times, that is the standard interpretation of what superposition means. When someone who does not understand QM and ask such a question, that is what you have to provide.

Whether it makes any sense or not, that is no longer physics but a matter of tastes. I find it to make perfect sense if one abandons the notion of a "classical particle" that has definite physical boundary. So what does not makes sense to you can make perfect sense to someone else. This is what I meant as simply a matter of tastes, so arguing about something based on one's sense doesn't mean anything. Besides, since when has making sense been infallible?

Zz.

 

[Crosson]

The superposition of states where all the orthorgonal states are present in the description of the system has always been interpreted as having those states simultaneously. That's the "paradox" of the schrodinger cat system.

No, that is the popularization of the paradox. If you read the original paper, Schrodinger is concerned with the transition from quantum superpositions to classical mixtures. He is not talking about how to interpret the superposition state, he is pointing out that quantum mechanics paradoxically predicts superposition states instead of mixtures.

You and I, with the benefit of 70 years of physics since Schrodinger, know that superpositions become mixtures because of decoherence, and so the paradox is resolved.

It is not my interpretation. I'm giving the prevailing view of what has been written as the description of superposition. If you look at all the papers, including the Leggett paper that I've mentioned several times, that is the standard interpretation of what superposition means. When someone who does not understand QM and ask such a question, that is what you have to provide.

I agree that we should provide the standard answer. I don't see you referring to the Legget paper in this thread, so I searched google and of course your blog post on this topic came up:

http://physicsandphysicists.blogspot.com/2006/10/schrodinger-cat-type-experiments.html"

I followed the only link that leads to a freely accessible paper:

http://arxiv.org/abs/cond-mat/0004293"

I read the entire paper, but did not find any evidence to support what you are calling the 'standard interpretation.' All of the wording in this paper is consistent with what I know about quantum mechanics, e.g.

"Here we present the first experimental evidence that a superconducting quantum interference device (SQUID) can be put into a superposition of twomagnetic-flux states, one corresponding to a few micro-amperes of current flowing clockwise, the other cor-
responding to the same amount of current flowing counterclockwise."

Great, they put it in a superposition of both states, (A + B). This is very different from saying they put it in state A and state B simultaneously (again, I wouldn't even know how to interpret the latter within the formalism).

Again from the article:

"Such a superposition would manifest itself in an anticrossing, as illustrated in Figure 1b, where the energy level diagram of two levels of different flux states (labelled
|0i and |1i) is shown in the neighbourhood in which they would become degenerate without coherent interaction (dashed lines). Coherent tunnelling lifts the degeneracy
(solid lines) so that at the degeneracy point the energy eigenstates are close to 1 √2
(|0i + |1i) and 1 √2(|0i − |1i) , the symmetric and antisymmetric superpositions."

In other words, they don't measure the superposition by measuring two currents going in opposite directions, they measure it directly by its properties as a superposition.

Whether it makes any sense or not, that is no longer physics but a matter of tastes. So what does not makes sense to you can make perfect sense to someone else. This is what I meant as simply a matter of tastes, so arguing about something based on one's sense doesn't mean anything. Besides, since when has making sense been infallible?

Making sense is not always infallible, but in contrast not making sense is always fallible. If a particle is in the state:

psi = a*v1 + b*v2

then it does not make sense to say that the particle is also simultaneously in the states

psi = v1

and

psi = v2

Since all three of these states are totally distinct. We already know exactly what state the particle is in:

psi = a*v1 + b*v2

And we can measure all the properties of the particle in this state.

I find it to make perfect sense if one abandons the notion of a "classical particle" that has definite physical boundary.

That's fine, but then you must agree that it is sensationalist to say "the electron is in two places at once" since if it has no definite physical boundary then it has no definite location.

As for your abandoning the notion of a classical particle, this disagrees with the established standard interpretation in textbooks, e.g.

"In QED, the electron is point-like particle." -- Griffiths, Introduction to Elementary Particles

I also think the spread-out electron is untenable. In basic QM you could think of the electron as spread out in the form of the magnitude of its position space wave function, but what do you do in QFT?

 

[reilly]

The superposition of states where all the orthorgonal states are present in the description of the system has always been interpreted as having those states simultaneously. That's the "paradox" of the schrodinger cat system.
Zz.

Historically this is not true. See, for example, Kemble's QM text, which was very influential during the 30s. He, as do many other authors, simply uses the conventional interpretation of probability, given the probability measure W*(x)W(x) dV(x). So, interpreting, as you do, a superposition as representing a particle in many positions at once is, in fact, contrary to centuries of common practice in probability theory -- unless you are considering a statistical ensemble (sample space) in which case you can talk about two particles being at the same place at the same time.

How would you compute the probability of a particle being in two places at the same time?
Regards,
Reilly

 

[ZapperZ]

No, that is the popularization of the paradox. If you read the original paper, Schrodinger is concerned with the transition from quantum superpositions to classical mixtures. He is not talking about how to interpret the superposition state, he is pointing out that quantum mechanics paradoxically predicts superposition states instead of mixtures.

You and I, with the benefit of 70 years of physics since Schrodinger, know that superpositions become mixtures because of decoherence, and so the paradox is resolved.

I still disagree that this isn't a standard view, since, again, I've read it way too many times beyond just want Phillip Ball had written. For example:

http://www.sciam.com/article.cfm?id=schrdingers-squid
http://physicsworld.com/cws/article/news/2815
http://physicsworld.com/cws/article/print/525

I agree that we should provide the standard answer. I don't see you referring to the Legget paper in this thread, so I searched google and of course your blog post on this topic came up:

http://physicsandphysicists.blogspot.com/2006/10/schrodinger-cat-type-experiments.html"

I followed the only link that leads to a freely accessible paper:

http://arxiv.org/abs/cond-mat/0004293"

I read the entire paper, but did not find any evidence to support what you are calling the 'standard interpretation.' All of the wording in this paper is consistent with what I know about quantum mechanics, e.g.

"Here we present the first experimental evidence that a superconducting quantum interference device (SQUID) can be put into a superposition of twomagnetic-flux states, one corresponding to a few micro-amperes of current flowing clockwise, the other cor-
responding to the same amount of current flowing counterclockwise."

But to me, that is exactly saying the same current going in the opposite direction in the SQUID loop. The links I gave above (and I believe there is a News and Views article for one of the papers) interpreted it as such.

Great, they put it in a superposition of both states, (A + B). This is very different from saying they put it in state A and state B simultaneously (again, I wouldn't even know how to interpret the latter within the formalism).

Again from the article:

"Such a superposition would manifest itself in an anticrossing, as illustrated in Figure 1b, where the energy level diagram of two levels of different flux states (labelled
|0i and |1i) is shown in the neighbourhood in which they would become degenerate without coherent interaction (dashed lines). Coherent tunnelling lifts the degeneracy
(solid lines) so that at the degeneracy point the energy eigenstates are close to 1 √2
(|0i + |1i) and 1 √2(|0i − |1i) , the symmetric and antisymmetric superpositions."

In other words, they don't measure the superposition by measuring two currents going in opposite directions, they measure it directly by its properties as a superposition.

But that is the only way to detect such superposition, by either measuring the non-commuting observable, or the non-contextual observable. That's why this isn't a classical measurement where the "unknown state of our knowledge" has no physical manifestation that is measurable. This is also how we know the superposition description is valid. We don't detect an electron being localized at both H atom in the H2 molecule. We do, however, detect the effects via our measurement of the bonding-antibonding state. It's the same thing here.

Zz.

 

[ZapperZ]

Historically this is not true. See, for example, Kemble's QM text, which was very influential during the 30s. He, as do many other authors, simply uses the conventional interpretation of probability, given the probability measure W*(x)W(x) dV(x). So, interpreting, as you do, a superposition as representing a particle in many positions at once is, in fact, contrary to centuries of common practice in probability theory -- unless you are considering a statistical ensemble (sample space) in which case you can talk about two particles being at the same place at the same time.

But historically, an atom also looks like the Bohr atom.

How would you compute the probability of a particle being in two places at the same time?
Regards,
Reilly

I don't unless you consider the probability density of the wavefunction corresponds to such a quantity. This is no different than the smearing of the position of an electron in an atomic orbital. When 2 orbitals from two different atom hybridized, a single electron can localize itself at both locations when you have significant overlap of those orbitals. Tight-binding band structure calculations employ such a thing.

Look, I have ample problems with such interpretation and I can go on for pages on why I myself do not use such views. However, as I've mentioned in the previous post, it is THE prevailing view that when you have a "superposition of states", that ALL of those states are present simultaneously. The bell-type experiments is different from just a simple classical conservation of angular momentum case exactly because the superposition of the orthorgonal spin directions implies that the projection of the spin direction consists of all the possible spin states before measurement.

Zz.

 

[Crosson]

I still disagree that this isn't a standard view, since, again, I've read it way too many times beyond just want Phillip Ball had written. For example:

http://www.sciam.com/article.cfm?id=schrdingers-squid
http://physicsworld.com/cws/article/news/2815
http://physicsworld.com/cws/article/print/525

All three of these links are popularization articles. I agree that the first article supports your view, containing the following clear statement of what you call 'the standard interpretation':

In the new experiments, an electric current stood in for the cat and flowed both ways around a loop at the same time.

If you found a statement like this in a scientific article, or a graduate-level textbook, then I would be convinced. I too, however, have seen this kind of sensationalism in popularized articles, but I give infinitely more weight to the science I have learned from textbooks.

But to me, that is exactly saying the same current going in the opposite direction in the SQUID loop.

You must admit that the article does not exaclt say this, they use language more carefully to say that the particle is in a superposition, and then they describe the states that make up the superposition, exactly consistent with what I have learned from textbooks.

The links I gave above (and I believe there is a News and Views article for one of the papers) interpreted it as such.

As I said, these are popularizations. I appreciate you taking the effort to find and post them, but they are not definitive sources.

But that is the only way to detect such superposition, by either measuring the non-commuting observable, or the non-contextual observable. That's why this isn't a classical measurement where the "unknown state of our knowledge" has no physical manifestation that is measurable. This is also how we know the superposition description is valid. We don't detect an electron being localized at both H atom in the H2 molecule. We do, however, detect the effects via our measurement of the bonding-antibonding state. It's the same thing here.

I totally agree with this statement, we both know this.

 

[ZapperZ]

All three of these links are popularization articles. I agree that the first article supports your view, containing the following clear statement of what you call 'the standard interpretation':

In the new experiments, an electric current stood in for the cat and flowed both ways around a loop at the same time.

If you found a statement like this in a scientific article, or a graduate-level textbook, then I would be convinced. I too, however, have seen this kind of sensationalism in popularized articles, but I give infinitely more weight to the science I have learned from textbooks.

You must admit that the article does not exaclt say this, they use language more carefully to say that the particle is in a superposition, and then they describe the states that make up the superposition, exactly consistent with what I have learned from textbooks.

As I said, these are popularizations. I appreciate you taking the effort to find and post them, but they are not definitive sources.

But textbooks don't deal with such "interpretations". As I've mentioned many times on here, QM must be understood at the level of its formalism. Most of us who are in this field couldn't care less how such a thing is interpreted. I know I don't use such a thing in my daily work. However, when we describe it, this is where we invoke such interpretation. I know for a fact that Leggett himself has used the same words that I did in his seminars to describe what "superposition" implies. I will look again at his J. of Phys - Condens. Matt. paper when I get into work tomorrow and see if he has used it there as well.

Zz.

 

[Crosson]

But textbooks don't deal with such "interpretations". As I've mentioned many times on here, QM must be understood at the level of its formalism.

I totally agree, which is why I asked you in post #7 of this thread:

" What do you mean in terms of the formalism, 'has all the states'? "

Now I see that you are contrasting the formalism with the interpretation, which I hope you will agree is not something that they do a very good job in the popularizations that you linked (which only matters because that general trend is responsible for the OP asking this question).

Most of us who are in this field couldn't care less how such a thing is interpreted. I know I don't use such a thing in my daily work.

I agree that the phrase "in both states at the same time" does not have any effect on the calculations, and I am glad to hear that you (and, presumably, your colleagues) do not give much care towards what you call 'the standard interpretation.'

However, when we describe it, this is where we invoke such interpretation.

Why not just say 'is in a superposition state' ? Or do you mean when describing to someone who does not know the formalism?

I know for a fact that Leggett himself has used the same words that I did in his seminars to describe what "superposition" implies.

I believe you. It disappoints me slightly, but only in a way that someones politics, etc can detract from my admiration for their accomplishments in science.

I will look again at his J. of Phys - Condens. Matt. paper when I get into work tomorrow and see if he has used it there as well.

Zz, I really appreciate the effort you have put into show me evidence of the standard interpretation. Being familiar with some of your other threads, I know you have an accurate picture of the mainstream thinking in condensed matter physics.

In the future I will give a different response to the OP's question:

Is it literally possible for them to be in two places at once?

This is a widely held interpretation of the mathematical formalism of quantum mechanics, but there is no experiment to date that can confirm or deny the claim. In my opinion, this interpretation does not convey the subtleties of quantum superposition, and is excessively sensational.

 

[muppet]

In case the OP as been left confused by that debate...
In orthodox QM we don't really talk about the electron "being" in two places at once. In fact, we don't really talk about it "being" anywhere. We say that it is described by a wave function \Psi, a mathematical function that we can coerce into telling us the probability that we will find the particle in a particular place, or moving in a particular direction. There are certain kinds of functions called eigenfunctions that describe the particle being in a state that is physically allowed. Arguably the most bizarre thing about quantum mechanics is that most of the time, a particle isn't described by an eigenfunction, but by a linear combination of eigenfunctions; its wavefunction is that function you obtain by adding one eigenfunction to another, each function being multiplied by appropriate numbers so that you don't get probabilities greater than one. A particle described by such a linear combination of "allowed" states is said to be in a "superposition of states", and this is the origin of loose phrases such as "is in two places at once".
That much isn't really controversial (which you may find suprising!). What is controversial is whether or not nature really behaves in the way our maths seems to describe when we aren't looking; whether an electron really exists as some fuzzy, smeared-out field that decides to adopt definite values only when we decide to look for it. The part to which there are the most serious objections is the transition between a superposition of states and the particle we actually measure, a process known as the collapse of the wavefunction. Some people think it is physically real, but argue over what constitutes a measurement- some say it has to be carried out by a conscious observer, wheras some say any thermodynamically irreversible interaction with the environment will do. Some, however deny it, and instead claim that rather than the superposition of the particle collapsing, the observer instead is in a superposition of having measured all the possible values! This is the origin of talk you may have heard of the "many-worlds" interpretation. In one "world" the particle goes through one slit, in another it goes through the other, and the poor observer is split into two duplicates of himself, each identical in every detail except that memory corresponding to whether he believes the photon went through the left slit or the right one.
This may all seem deeply, deeply wierd. It is. Unfortunately (or interestingly, depending on your point of view) the experimental facts are so weird as to necessitate a weird explanation!

 

[lightarrow]

Is it literally possible for them to be in two places at once?

If this were true, the electron should be detected in the two places simultaneously, for example the two slits. This doesn't happen.
Another possible interpretation is that the electron "is not" here, or there, or in both places, before detecting it: it "is" where and when you detect it.

 

[ZapperZ]

If this were true, the electron should be detected in the two places simultaneously, for example the two slits. This doesn't happen.
Another possible interpretation is that the electron "is not" here, or there, or in both places, before detecting it: it "is" where and when you detect it.

I think you missed the point of the question here. It isn't after detection, because the act of detection will produce a classical result (the collapse of the wavefunction). You'll notice that all of the discussion so far has been about "superposition", which is the situation before a measurement. The effects of such superposition are evident in what we can measure indirectly of all those states via things ranging from the bonding-antibonding state and the coherence gap.

Zz.

 

[lightarrow]

I think you missed the point of the question here. It isn't after detection,

I know, and it's just for this reason that I express my personal doubts on the physical meaning of the fact that an electron could be somewhere before detection.

 

[Ciokko]

well..something should be in the place in which you detect the electron..

 

[lightarrow]

well..something should be in the place in which you detect the electron..

But this doesn't necessarily imply that the same thing was flying from source to detector through defined positions.

 

[Ciokko]

i mean that something should be there even before the detection, if not there is no reason to decect something in that place

 

[lightarrow]

i mean that something should be there even before the detection, if not there is no reason to decect something in that place

"There" where? Can you precise the spatial coordinates?

 

[Ciokko]

if your detector has a surface of detection, my coordinates are precisely "somewhere on that surface"

 

[lightarrow]

if your detector has a surface of detection, my coordinates are precisely "somewhere on that surface"

But with "somewhere" you mean in a precise point that we don't know or in every point simultaneously?

 

[peter0302]

Is it literally possible for them to be in two places at once?
Is this proven; How is this possible?

I mean, sure they travel very, very fast. Even if they travel faster than the speed of light, it would appear so that they are, but nothing can travel at a speed that literally freezes time [only apparently].

I think this hints more towards electrons traveling though another spatial dimension than traveling though time.

Another thread hijacked over the typical CI vs. everything else argument.

The answer is you will never find the electron in two places at once. If you find it somewhere, you know with certainty it's nowhere else.

The rest of your post is nonsense (no offense). Unless you're referring to Wheeler's idea that "there is only one electron", which I don't think is what you meant.

 

[Ciokko]

But with "somewhere" you mean in a precise point that we don't know or in every point simultaneously?

let's distinguish:
before detection, the electron is in a superposition, so its wave function is in different places simultaneously

after detection, the wave function collapses so we no longer have a superposition and the electron acts like a classical particle.

what i wanted to say in the previoulsy replies is that you can treat the electron's wave function like an abstract mathematical object:

I know, and it's just for this reason that I express my personal doubts on the physical meaning of the fact that an electron could be somewhere before detection.

but something (at least a simple information) should propagate physically, because if not there is no reason to detect the electron.
so, instead of consider the wave function and something else that propagates physically, let's treat the wave function like a physical object.
then, if you don't identify the wave function (of the electron) with the electron itself, this is just a matter of interpretation

 

[lightarrow]

but something (at least a simple information) should propagate physically, because if not there is no reason to detect the electron.

But this is different from saying: "well..something should be in the place in which you detect the electron.."

so, instead of consider the wave function and something else that propagates physically, let's treat the wave function like a physical object.
then, if you don't identify the wave function (of the electron) with the electron itself, this is just a matter of interpretation

Which physical meaning would you suggest for the wavefunction, in case you don't identify it with the electron itself?

 

[Ciokko]

But this is different from saying: "well..something should be in the place in which you detect the electron.."

no difference at all

Which physical meaning would you suggest for the wavefunction, in case you don't identify it with the electron itself?

actually, i identify the wave function with the electron itself...

 

[lightarrow]

Which physical meaning would you suggest for the wavefunction, in case you don't identify it with the electron itself?

actually, i identify the wave function with the electron itself...

Ok, so the electron's mass and charge are dispersed in space according to |psi|^2 or what?

 

[Ciokko]

so the electron, before the detection, acts like a wave...i really can't get your point...

 

[lightarrow]

so the electron, before the detection, acts like a wave...i really can't get your point...

That's true for every particle, but it's completely different from saying that the wavefunction "is" the electron.

 

[peter0302]

The set of possible places you might find the electron is defined by the wave function.

That's all we can say, with certainty, about a wave function. Anything more is interpretation. We can't say the electron "acts like a wave" "is a wave" or any other such hueristic, in any scientifically meaningful way.

 

[Maaneli]

<< That's all we can say, with certainty, about a wave function. Anything more is interpretation. We can't say the electron "acts like a wave" "is a wave" or any other such hueristic, in any scientifically meaningful way. >>

Actually we can say what the electron is or acts like before measurement, in a scientifically meaningful way.

 

[Maaneli]

<< You and I, with the benefit of 70 years of physics since Schrodinger, know that superpositions become mixtures because of decoherence, and so the paradox is resolved. >>

This sounds like nonsense. Can you justify this statement with some physics?

 

[peter0302]

Actually we can say what the electron is or acts like before measurement, in a scientifically meaningful way.

Perhaps it's meaningful to you in your head, but that's it.

 

[Maaneli]

Perhaps it's meaningful to you in your head, but that's it.

Actually no. It is just as meaningful as saying that a particle is a particle in classical mechanics, even before it is measured. This point can be tested and justified in a number of different ways. In particular, one can test such an interpretation by how much more it explains than another interpretation

 

[muppet]

You can certainly say that the electron is "acts like a wave" in a perfectly scientific way. The results of experiments strongly(!) support the idea that the electron's wavefunction undergoes diffraction, interference, superposition, and other wavelike phenomena. Whether you say that the wavefunction "is" the electron or "describes it" is what we can't answer, but I see nothing wrong whatever with characterising experimentally observable behaviour by analogy.

You can't "test" an interpretation, however. The definition of an interpretation is effectively the physical picture that we associate with the mathematical description of the results of observable measurement. You cannot discriminate between theories that make identical predictions using any apparatus of the scientific method. As soon as something makes distinct experimental prediction from a theory, it ceases to become an interpretation of that theory and becomes a distinct, falsifiable theory. Until such time, you're ultimately picking whichever description accords with your intuition about a particular topic.

 

[Maaneli]

why was the exchange between me and Crosson removed?

 

[peter0302]

The reason mathematics, not English, is the language of physics is because mathematics is the only language in which you can say unambiguous things in a scientifically accurate way.

"Acts like a wave" is subject to so much interrpetation that it does no good in predicting or understanding a particle's behavior. When we must speak in English, we try to do so using the most unambiguous exact terminology possible. Again, "acts like a wave" doesn't cut it.

The wave function describes the likely locations one will observe a particle. The wave function is governed by the Schrodinger Equation. That's the best you can do before you get into ambiguities and philosophies.

 

[Maaneli]

The reason mathematics, not English, is the language of physics is because mathematics is the only language in which you can say unambiguous things in a scientifically accurate way.

"Acts like a wave" is subject to so much interrpetation that it does no good in predicting or understanding a particle's behavior. When we must speak in English, we try to do so using the most unambiguous exact terminology possible. Again, "acts like a wave" doesn't cut it.

The wave function describes the likely locations one will observe a particle. The wave function is governed by the Schrodinger Equation. That's the best you can do before you get into ambiguities and philosophies.

No, it isn't the best you can do. You can do better:

\frac{dQ_{k}}{dt} = \frac{\hbar}{m}\Im\frac{\left\{\nabla\psi\right\}}{\psi}\left(Q_{1}...Q_{k}\right)

This is the de Broglie-Bohm guidance equation for a point particle, whose velocity vector is clearly determined in part by the wavefunction. Therefore we have a perfectly mathematically rigorous way to speak of the electron as a particle 'guided' by a wave.

 

[peter0302]

Bohmian Mechanics is an interpretation of QM, not an accepted or even testable theory.

You seem to have your own ideas about things and no interest in doing anything but espousing them, so there's not much point in continuing this discussion.

 

[Maaneli]

Bohmian Mechanics is an interpretation of QM, not an accepted or even testable theory.

You seem to have your own ideas about things and no interest in doing anything but espousing them, so there's not much point in continuing this discussion.

First off, the equation I wrote down is a sharp counterexample to your mistaken belief that the Schroedinger evolution is all that one can meaningfully talk about regarding the electron, because you think it is the only mathematically well-defined statement about its physics. Also you seem to not realize that the wave function is itself not an observable field, even in standard QM.

In the first place, BM (should actually be referred to as de Broglie-Bohm theory) is not just an "interpretation" of QM, but a different formulation of QM. It involves different equations than standard QM. And it is completely false to say that it is "not an accepted or even testable theory". No single formulation or interpretation of QM (including the textbook plus decoherence approach) is accepted as "the most correct" by most physicists; but physicists who have studied the pilot wave theory admit it is self-consistent and empirically equivalent to standard QM, even if they don't like it for whatever reason. As for it being testable, indeed it is for the possibility of quantum nonequilibrium dynamics:

Dynamical Origin of Quantum Probabilities
Antony Valentini and Hans Westman
http://eprintweb.org/S/authors/All/va/Valentini/12

De Broglie-Bohm Prediction of Quantum Violations for Cosmological Super-Hubble Modes
Antony Valentini
http://eprintweb.org/S/authors/All/va/Valentini/2

Inflationary Cosmology as a Probe of Primordial Quantum Mechanics
Antony Valentini
http://eprintweb.org/S/authors/All/va/Valentini/1

Furthermore, these are not my "own ideas", and the fact that you would characterize them like that as a way to dismiss them or refuse to acknowledge them tells me that you don't and are not really interested in understanding anything different from a naive textbook approach to QM.

The ball is in your court now. I gave you a sharp counterexample to your claims that pilot wave theory is not testable or "accepted", and it is up to you to show a dignified response.

 

[Maaneli]

The reason mathematics, not English, is the language of physics is because mathematics is the only language in which you can say unambiguous things in a scientifically accurate way.

Based on this alone you should agree with me that the pilot wave theory can say "unambiguous things in a scientifically accurate way", since it is framed in precise mathematical language, not just words.

"Acts like a wave" is subject to so much interrpetation that it does no good in predicting or understanding a particle's behavior. When we must speak in English, we try to do so using the most unambiguous exact terminology possible. Again, "acts like a wave" doesn't cut it.

What does it mean for you to "understand" a particle's behavior, in distinction from predicting its behavior?

The wave function describes the likely locations one will observe a particle. The wave function is governed by the Schrodinger Equation. That's the best you can do before you get into ambiguities and philosophies.

So hopefully you understand now that there is no ambiguity or philosophy in writing down a differential equation of motion for a point particle like I did earlier.

 

[reilly]

First off, the equation I wrote down is a sharp counterexample to your mistaken belief that the Schroedinger evolution is all that one can meaningfully talk about regarding the electron, because you think it is the only mathematically well-defined statement about its physics. Also you seem to not realize that the wave function is itself not an observable field, even in standard QM.

In the first place, BM (should actually be referred to as de Broglie-Bohm theory) is not just an "interpretation" of QM, but a different formulation of QM. It involves different equations than standard QM. And it is completely false to say that it is "not an accepted or even testable theory". No single formulation or interpretation of QM (including the textbook plus decoherence approach) is accepted as "the most correct" by most physicists; but physicists who have studied the pilot wave theory admit it is self-consistent and empirically equivalent to standard QM, even if they don't like it for whatever reason. As for it being testable, indeed it is for the possibility of quantum nonequilibrium dynamics:

Dynamical Origin of Quantum Probabilities
Antony Valentini and Hans Westman
http://eprintweb.org/S/authors/All/va/Valentini/12

De Broglie-Bohm Prediction of Quantum Violations for Cosmological Super-Hubble Modes
Antony Valentini
http://eprintweb.org/S/authors/All/va/Valentini/2

Inflationary Cosmology as a Probe of Primordial Quantum Mechanics
Antony Valentini
http://eprintweb.org/S/authors/All/va/Valentini/1

Furthermore, these are not my "own ideas", and the fact that you would characterize them like that as a way to dismiss them or refuse to acknowledge them tells me that you don't and are not really interested in understanding anything different from a naive textbook approach to QM.

The ball is in your court now. I gave you a sharp counterexample to your claims that pilot wave theory is not testable or "accepted", and it is up to you to show a dignified response.

I agree with peter0302, he's got it right,in spite of his alleged naivety and
I support his notions( in fact, if you read his posts, you'll find him to be quite sophisticated)
Dignified?, not to worry.

Can this alternate theory allow us to
1. compute the electron's magnetic moment to 13 decimal places as is done with standard QED, 2. compute the pion-nucleon scattering S-matrices; 3. derive the Fermi-Thomas approximation, or equivalent thereof, used in atomic physics(heavy elements)4. can this approach bring anything new to the issue of quark containment?

Please: How about an example or two of an "naive textbook approach.

You want dignity in response to calling someone "naive"? Hmmm Am I missing something?
Regards,
Reilly Atkinson

 

[Maaneli]

Can this alternate theory allow us to
1. compute the electron's magnetic moment to 13 decimal places as is done with standard QED, 2. compute the pion-nucleon scattering S-matrices; 3. derive the Fermi-Thomas approximation, or equivalent thereof, used in atomic physics(heavy elements)4. can this approach bring anything new to the issue of quark containment?

1. Yes.

2. Yes.

3. Yes.

4. No so clear yet if it gives us the same answers or something new.

You have to understand that throwing out specific examples like that is not a challenge to the alternate theory if you understand how that alternate theory works in the slightest. Also, I already referenced new predictions of pilot wave theory that the standard QM or QED cannot make. So there.

And I have to disagree with you about Peter's sophistication. He clearly refused to admit an alternative possibility that is just as mathematically rigorous as what he thinks.

 

[peter0302]

Well, I certainly appreciate the compliment Reilly, and especially coming from someone as knowledgeable as yourself that's means a lot. :)

As for Maaneli's comments, I certainly did not literally mean that the Schrodinger equation is the only mathematically correct QM equation. (I would have been remiss, for example, if I had ignored the Dirac equation or all of QED for that matter).

My point is that there is a stark difference between saying something "acts like a wave" and saying that a particle's probability density amplitude - i.e. wave function - is governed by the Schrodinger equation. One is a hueristic, the other is a mathematical statement. One conveys testable, reproducible information; the other conveys philosophy and ambiguity.

Regarding the DeBroglie-Bohm pilot wave hypothesis (aka Bohmian Mechanics), it is not a scientific theory any more than Intelligent Design is a scientific theory. Both purport to explain the observable phenomina. Neither can be tested (at this time) using the methods of science.

To state that evidence of a theory includes its ability to explain everything countermands the fundamental tenets of science itself. Anyone can sit down with a bottle of Jack and come up with an elaborate explanation for everything. That does not make it true. The measure of a theory is its ability to make accurate predictions, not to explain. Moreover, that the theory makes accurate predictions does not make it right - it merely makes it not wrong. In other words, science can merely rule out theories; it cannot prove them (ironically, all science can do is "prove negatives").

The inherent weakness of any quantum interpretation is that it, by definition, must account for all known results. Therefore, that Bohmian Mechanics, for example, can make the same predictions as QFT is not an argument in its favor. Show me an interpretation that explains everything else, and makes new predictions about things we haven't seen yet, that turn out to be right, and I'll be the first in line to support their Nobel nomination.

One slight exception that I will give you would be an Occam's razor-type argument, that is, if two competing interpretations are offered and one makes significantly fewer assumptions, than it is the more favorable view. However, no current quantum interpretation is clearly the winner in this respect (though some, like the Cramer TI idea, probably are clear losers).

That is how I justify my statement that all we can say about the behavior of the electron is that the location where we are likely to find it is governed by the wave function - and that any other statements are, at this time, not scientifically meaningful.

Now, not to be thought of as hypocritical, I frequently enjoy discussing the merits of various QM interpretations. For one thing, I, like many people, do indeed wish there was an explanation for what we see. Further, I hold out hope that some, if not many of the competing interpretations out there will eventually be mature enough to become genuine theories that make testable predictions. And, like anyone else, I enjoy a little bit of philosophy here and there.

*But* when I talk about an interpretation, I attempt to always do so in the _context_ of an interpretative discussion, and never to be making factual or scientific assertions. I probably have crossed the line sometimes, but I aim not to.

Maaneli, the reason I criticized your psots is because you do not seem to be attempting to make any kind of distinction between predictive science and philosophy/interpretation. Moreover, putting the DeBroglie-Bohm quantum potential formula out there as an example of what we can say the electron is doing before detection (which is how I interpreted your point) is misleading.

So, I stand by what I originally said and hope that I've persuaded you that your views on this matter contain more interpretive than scientific opinions.

 

[Maaneli]

Regarding the DeBroglie-Bohm pilot wave hypothesis (aka Bohmian Mechanics), it is not a scientific theory any more than Intelligent Design is a scientific theory. Both purport to explain the observable phenomina. Neither can be tested (at this time) using the methods of science.

OK, you just lost all credibility on this discussion by comparing deBB to ID, and in calling deBB a hypothesis and not a scientific theory. That would be like comparing textbook QM to ID. Regardless of what ID purports, it doesn't explain or predict ANYTHING. deBB theory on the other hand, explains and predicts everything in QM observed thus far. My guess is that you don't understand either deBB theory or ID. Also, it is clear that you did not bother to even look at the papers I cited as proof that deBB theory makes new predictions that are testable.

The inherent weakness of any quantum interpretation is that it, by definition, must account for all known results. Therefore, that Bohmian Mechanics, for example, can make the same predictions as QFT is not an argument in its favor.

That deBB field theory makes the same predictions as standard QFT is an argument for why it is at least as good to use as standard QFT. That is contrary to what many people think, yourself included it seems.

Show me an interpretation that explains everything else, and makes new predictions about things we haven't seen yet, that turn out to be right, and I'll be the first in line to support their Nobel nomination.

I did show you. Look at those damn papers I cited.

One slight exception that I will give you would be an Occam's razor-type argument, that is, if two competing interpretations are offered and one makes significantly fewer assumptions, than it is the more favorable view. However, no current quantum interpretation is clearly the winner in this respect (though some, like the Cramer TI idea, probably are clear losers).

I might agree with you here. But I hope we can agree that among competing interpretations, the CI interpretation is clearly the worst by an Occam's razor type argument, in comparison to pilot wave theory, GRW collapse theory, decoherence theory, stochastic mechanics, MWI, and others.

Further, I hold out hope that some, if not many of the competing interpretations out there will eventually be mature enough to become genuine theories that make testable predictions.

Look at those papers.

Maaneli, the reason I criticized your psots is because you do not seem to be attempting to make any kind of distinction between predictive science and philosophy/interpretation.

Yes I did make such a distinction.

Moreover, putting the DeBroglie-Bohm quantum potential formula out there as an example of what we can say the electron is doing before detection (which is how I interpreted your point) is misleading.

I wrote down the guidance equation NOT the quantum potential. Those are two different things, and the former is more fundamental than the latter in deBB theory.

So, I stand by what I originally said and hope that I've persuaded you that your views on this matter contain more interpretive than scientific opinions.

You haven't because you haven't understood my views in this matter in the first place.

I appreciate that you tried to explain yourself though.

 

[peter0302]

Well, as far as the papers you've posted, I don't know if they've been peer reviewed or published, but it looks to me like they haven't. There is so much misinformation out there that, frankly, yes, I don't bother to read things unless they're published, peer reviewed, and (often) explained by people here who understand the math much better than I. If they are indeed as groundbreaking as you say they are, surely they will change the course of physics.

Out of curiosity, are you Antony Valentini?

 

[Maaneli]

Well, as far as the papers you've posted, I don't know if they've been peer reviewed or published, but it looks to me like they haven't. There is so much misinformation out there that, frankly, yes, I don't bother to read things unless they're published, peer reviewed, and (often) explained by people here who understand the math much better than I. If they are indeed as groundbreaking as you say they are, surely they will change the course of physics.

Out of curiosity, are you Antony Valentini?

No I'm not Valentini. BTW, two of those papers were just posted in the past 3 months. But Valentini is highly respected in quantum foundations circles, is considered a world expert on pilot wave theory, has been a major player in the MWI vs Pilot wave theory debates, and is a former research associate at the Perimeter Institute on the support of Lee Smolin, and is now in the foundations and cosmology group with Dowker and Magueijo at the Imperial College. And yes he has published quite a few works. That should be sufficient for you to trust his credibility on this subject.

To be honest, I get the sense that you're trying to BS your way out of looking at those papers and admitting you made mistakes. You didn't even bother to admit your mistakes about your comments on the other thread.