A electron can exist in everywhere ?

[big_bounce]

Hello all .
In quantum physics there are any theory that says a electron or Partial of electron exist in everywhere in universe ?
Means a electron in other side me can exist Partial of it in 300000 light year ?

 

[dextercioby]

There's no such thing as a part of an electron, not according to the commonly accepted (textbook material) theories.

 

[Khashishi]

The wave function of an electron can exist everywhere. But the observed position is just in one spot. The electric field from the electron also extends indefinitely far in its light cone.

 

[AbsoluteZer0]

Quantum superposition states that a physical system, in your case an electron, exists in all of its possible configurations simultaneously. However, when observed or measured, the results of the measurement correspond to only one of the possible states.

 

[G-sound]

Particles being everywhere - is this a compelling reason to question that the world might be fake and not real?

 

[Amok]

Particles being everywhere - is this a compelling reason to question that the world might be fake and not real?

Not really, I don't really see the connection, lol :D

 

[G-sound]

Not really, I don't really see the connection, lol :D

Particles being everywhere at once. This isn't the world we encounter daily, is it? Particles are supposed to have positions and velocities, or at least that's what my experience so far suggests.

 

[Drakkith]

Particles being everywhere at once. This isn't the world we encounter daily, is it? Particles are supposed to have positions and velocities, or at least that's what my experience so far suggests.

The particles are not everywhere at once. The WAVEFUNCTION, which is a mathematical formula used to predict where the electron MIGHT be, says it has a range of locations. This does not mean that the electron will be in two places at once. If you interact with the electron, it will only be in one place at a time.

 

[G-sound]

The particles are not everywhere at once. The WAVEFUNCTION, which is a mathematical formula used to predict where the electron MIGHT be, says it has a range of locations. This does not mean that the electron will be in two places at once. If you interact with the electron, it will only be in one place at a time.

Aren't wavefunction and particle 2 aspects of the same thing?

 

[Amok]

Particles being everywhere at once. This isn't the world we encounter daily, is it? Particles are supposed to have positions and velocities, or at least that's what my experience so far suggests.

So what you mean is that what we observe is actually not real, but some underlying world is?

Aren't wavefunction and particle 2 aspects of the same thing?

No. A particle (or a group of particles) has a wavefunction. I think you're getting confused because people talk about wave-particle duality, wherein particles display both particule and wave behaviors. However, particles in quantum physics do not have the same meaning as in classical physics (very tiny solid objects) and a wavefunction isn't a classical wave either.

 

[G-sound]

No. A particle (or a group of particles) has a wavefunction. I think you're getting confused because people talk about wave-particle duality, wherein particles display both particule and wave behaviors. However, particles in quantum physics do not have the same meaning as in classical physics (very tiny solid objects) and a wavefunction isn't a classical wave either.

Are you claiming that the wave nature of particles is a myth? What exactly are you saying - that particles can behave as waves but the wave nature isn't real? That makes no sense, you are contradicting yourself. Either the wave nature of particles is real or it isn't. For consistency reasons, you can only choose one not both and argue both ways.

 

[Amok]

Are you claiming that the wave nature of particles is a myth? What exactly are you saying - that particles can behave as waves but the wave nature isn't real? That makes no sense, you are contradicting yourself. Either the wave nature of particles is real or it isn't. For consistency reasons, you can only choose one not both and argue both ways.

No, I'm saying a particle (in the quantum sense of the word), can display both wave-like and particle-like behavior (in the classical sense of the word). A wavefunction is not a wave though.

 

[Drakkith]

Are you claiming that the wave nature of particles is a myth? What exactly are you saying - that particles can behave as waves but the wave nature isn't real? That makes no sense, you are contradicting yourself. Either the wave nature of particles is real or it isn't. For consistency reasons, you can only choose one not both and argue both ways.

He said nothing of the sort. The wave-like properties of an electron are because of the wavefunction. (Or rather, the wavefunction is because the electron has wave-like properties) But you cannot say that the particles is located everywhere that the wavefunction says it might be at, because when we measure it we only detect it in one place.

 

[G-sound]

You are both not addressing the question i raised.

"because when we measure it we only detect it in one place. " ...doesn't address the issue of whether particles and reality exist at all times and esp. before detection. The fact that an electron is calculated and verified experiemntally to behave exactly according to qm rules suggests that the electron is in all of its possible positions. Or if you argue that the wavefunction isn't real, then only detections are real(reality isn't real), which is the same answer just coming from the opposite direction.

 

[Amok]

The fact that an electron is calculated and verified experiemntally to behave exactly according to qm rules suggests that the electron is in all of its possible positions.

That's just not true.

Moreover, an electron can exist before you detect it, and it can be in a superposition of states, which doesn't necessarily mean that it 'exists several places at once'.

G-sound, bear in mind that we cannot measure or otherwise observe the wavefunction itself, it is not a physical object, it's a mathematical abstraction from which we can extract information about the current state a of a particle or system of particles.

 

[Drakkith]

You are both not addressing the question i raised.

"because when we measure it we only detect it in one place. " ...doesn't address the issue of whether particles and reality exist at all times and esp. before detection. The fact that an electron is calculated and verified experiemntally to behave exactly according to qm rules suggests that the electron is in all of its possible positions. Or if you argue that the wavefunction isn't real, then only detections are real(reality isn't real), which is the same answer just coming from the opposite direction.

This has nothing to do with "reality existing". No matter what our theory says it's obvious reality exists, even if we describe it incorrectly.

As to whether the particle itself exists everywhere at the same time is...complicated. First, we would need to decide what that even means. To date I don't believe anyone has been able to come up with an accepted interpretation of what the wavefunction means in a non-mathematical way.

 

[G-sound]

No, I'm saying a particle (in the quantum sense of the word), can display both wave-like and particle-like behavior (in the classical sense of the word). A wavefunction is not a wave though.

When it acts as if it's in all possible states at once in the universe, and some pretty complicated machinary depends on this wave nature of electrons, what does it say about the world?

 

[G-sound]

This has nothing to do with "reality existing". No matter what our theory says it's obvious reality exists, even if we describe it incorrectly.
.

I'd say you are right that it exists though I am far less certain how and when it does.

 

[Drakkith]

When it acts as if it's in all possible states at once in the universe, and some pretty complicated machinary depends on this wave nature of electrons, what does it say about the world?

That the particle obeys the mathematical laws developed by QM. That's it.

I'd say you are right that it exists though I am far less certain how and when it dose.

Please, leave ramblings on reality out of this thread. They don't pertain to the thread at all and only serve to confuse people.

 

[Amok]

When it acts as if it's in all possible states at once in the universe, and some pretty complicated machinary depends on this wave nature of electrons, what does it say about the world?

It never acts (it is never seen, or measured to be) as if it were in many different states at once. That's one of the founding concepts of quantum mechanics. Whether the particle actually is in superposition of states when it is not observed is a question of philosophy. I still don't see how this has anything to do with the reality of our world, because that electron is still real, whether it is in a superposition of states or not.

 

[G-sound]

That the particle obeys the mathematical laws developed by QM. That's it.

No, all physical laws should describe the world we observe. If they describe differently, then either the laws are wrong or the world we observe isn't quite the idea we have of it.

 

[G-sound]

It never acts (it is never seen, or measured to be) as if it were in many different states at once. That's one of the founding concepts of quantum mechanics. Whether the particle actually is in superposition of states when it is not observed is a question of philosophy. I still don't see how this has anything to do with the reality of our world, because that electron is still real, whether it is in a superposition of states or not.

Is a bacteria in superposition real? What about something even bigger? By 'real' do you mean just what is observed or do you also include things that are not? If the former, why did you even try to muddle the question i asked?

 

[Amok]

No, all physical laws should describe the world we observe.

And they do, quantum mechanics is a theory about what we observe, exclusively about that actually. No can observe electrons in a superposition of states, for example, and qm doesn't say you can.

Is a bacteria in superposition real? What about something even bigger? By 'real' do you mean just what is observed or do you also include things that are not?

Bacteria aren't really described by quantum physics, as far as I know. I'm not saying that only things that we observe are real, and that things in superpositions aren't real. An electron is real whether it is in a superposition of states or not. Is the superposition itself ever real? No clue, no one knows.

 

[G-sound]

And they do, quantum mechanics is a theory about what we observe, exclusively about that actually. No can observe electrons in a superposition of states, for example, and qm doesn't say you can.

As i said earlier, the wave nature of electrons is widely utilized these days. If it were just a mathematical trick, qm would reduce to classical mechanics. I think you might be confused that classical objects and quantum ones are similar.

PP. I'd say that people trying to prove objective reality solely on qm have already lost the battle.

 

[Drakkith]

As i said earlier, the wave nature of electrons is widely utilized these days. If it were just a mathematical trick, qm would reduce to classical mechanics. I think you might be confused that classical objects and quantum ones are similar.

I think you should look and see what superposition really is. No one here is saying that the wave nature of electrons doesn't exist or is a trick.

PP. I'd say that people trying to prove objective reality solely on qm have already lost the battle.

How so?

 

[G-sound]

I think you should look and see what superposition really is.

Tell me.

No one here is saying that the wave nature of electrons doesn't exist or is a trick.

Tell me what it is you are saying, not what you are not saying. You've beeen saying that reality is real because we obviously observe it(great argument) and because when you detect it, you've found it to exist(how surprizing). If the wave nature of electrons is real and exists as you suggest, electrons are not localized in spacetime and this violates known laws and principles of classical physics(as well as the notion of objective reality)

How so?

First look up the commonly established criteria for objective reality and compare them with qm. You might want to read a bit on qm before you start with the criteria though.

 

[Drakkith]

Tell me.

There are plenty of references online that a quick google search will provide. Have you read any of those? Have you read more than one source? If so, what questions do you have about it?

Tell me what it is you are saying, not what you are not saying. You've beeen saying that reality is real because we obviously observe it(great argument) and because when you detect it, you've found it to exist(how surprizing).

No, nothing about measuring the electron has been construed into being something about reality. Reality is, arguable, ill defined and not appropriate for discussion as such. What we HAVE been saying is that the wavefunction PREDICTS WHERE THE PARTICLE WILL BE. That's it. You've misconstrued that into saying "particles don't behave like waves". This is not true, as we've explained more than once.

If the wave nature of electrons is real and exists as you suggest, electrons are not localized in spacetime and this violates known laws and principles of classical physics(as well as the notion of objective reality)

They appear in one place, and ONLY one place whenever we interact with and detect them. QM says nothing about them "spreading out" over space. That is only the wavefunction, where they may appear next. As I've said already we have NO interpretation of what the wave function is, other than a mathematical tool, that is widely accepted as the "best" interpretation. As far as I know at least.

First look up the commonly established criteria for objective reality and compare them with qm. You might want to read a bit on qm before you start with the criteria though.

I'm not going to play this game. Either explain what you mean, or don't bother posting it.

 

[G-sound]

There are plenty of references online that a quick google search will provide. Have you read any of those? Have you read more than one source? If so, what questions do you have about it?

You said i had to learn more about superposition, now you are asking what i want to know about it?

No, nothing about measuring the electron has been construed into being something about reality. Reality is, arguable, ill defined and not appropriate for discussion as such. What we HAVE been saying is that the wavefunction PREDICTS WHERE THE PARTICLE WILL BE. That's it.

No, you are wrong. The wave nature is not just a mathematical trick for predicting where a particle might be. It's an aspect of what a particle is and a particle is actually both a wave and a particle. Diodes, transistors, electron microscopes... all use the wave aspect of electrons, so saying that its wave nature is just a calculational trick is just plain wrong.

You've misconstrued that into saying "particles don't behave like waves". This is not true, as we've explained more than once.

I've said no such thing.

They appear in one place, and ONLY one place whenever we interact with and detect them. QM says nothing about them "spreading out" over space.

Look up Heisenberg's uncertainty principle, also the spreading out is part of nature and the basis of modern electronics. Furthermore, look for "devices that use qunatum mechanics" on google to get a better idea how much of a role the wave nature of particle plays these days.

I'm not going to play this game. Either explain what you mean, or don't bother posting it.

I'd use the reality criterion that Einstein, Podolsky and Rosen chose for their attempt to prove qm was incomplete, that later turned against them with Bell/Aspect. It was a case of reductio ad absurdum on their side that to their dismay turned true.

Whether the wavefunction is real or not doesn't change the core of the argument - we have an excellent theory with verified predictions but the predictions go against common sense and preconceived notions that most people consider obvious and true - like chairs, tables, cats and moons...

 

[Drakkith]

No, you are wrong. The wave nature is not just a mathematical trick for predicting where a particle might be. It's an aspect of what a particle is and a particle is actually both a wave and a particle. Diodes, transistors, electron microscopes... all use the wave aspect of electrons, so saying that its wave nature is just a calculational trick is just plain wrong.

I give up. If you are going to take everything out of context, not listen, not put the effort into learning, and accuse us of saying things we haven't then I will have no more of this thread.

Look up Heisenberg's uncertainty principle, also the spreading out is part of nature and the basis of modern electronics. Furthermore, look for "devices that use qunatum mechanics" on google to get a better idea how much of a role the wave nature of particle plays these days.

A perfect example of what I just said.

 

[Amok]

I feel like he's trolling us. Repeating stuff he read somewhere else without understanding it.

 

[ZapperZ]

And they do, quantum mechanics is a theory about what we observe, exclusively about that actually. No can observe electrons in a superposition of states, for example, and qm doesn't say you can.



Bacteria aren't really described by quantum physics, as far as I know. I'm not saying that only things that we observe are real, and that things in superpositions aren't real. An electron is real whether it is in a superposition of states or not. Is the superposition itself ever real? No clue, no one knows.

This is highly incorrect.

Note that we observe and measure the consequences of superposition. The existence of bonding-antibonding in chemistry is one clear example! Furthermore, I've mentioned the Delft/Stony Brook SQUID experiments in this forum a gazillion times already. I'd like someone to tell me that the presence of the coherence gap that they measure is NOT due to such superposition. Or better yet, write a rebuttal to those two papers, if you will!

People seem to forget that when you make a measurement, what you have "collapsed" is only the information related to THAT OBSERVABLE! If another observable is non-commuting, you've done nothing to destroy the superposition of that observable! And this is what we can take advantage of in trying to detect such superposition, and this is what has been done in the numerous Schrodinger Cat-type experiments. Anyone can do a search on the 'net on these types of experiments before making such silly claim that we don't know if such superposition is real or not!

Zz.

 

[Amok]

The existence of bonding-antibonding in chemistry is one clear example!

How so?

Furthermore, I've mentioned the Delft/Stony Brook SQUID experiments in this forum a gazillion times already. I'd like someone to tell me that the presence of the coherence gap that they measure is NOT due to such superposition. Or better yet, write a rebuttal to those two papers, if you will!

I'd never heard about that, but I'll check it out.

you've done nothing to destroy the superposition of that observable!

Sure, but you haven't observed it either.

And this is what we can take advantage of in trying to detect such superposition, and this is what has been done in the numerous Schrodinger Cat-type experiments. Anyone can do a search on the 'net on these types of experiments before making such silly claim that we don't know if such superposition is real or not!
Zz.

I'm sorry, no need to get all up in arms about it. I was taking an unassuming position to respond to a guy who was obviously rambling because wether or not superposition is real it has nothing to do with the existence of reality.

 

[ZapperZ]

Hello all .
In quantum physics there are any theory that says a electron or Partial of electron exist in everywhere in universe ?
Means a electron in other side me can exist Partial of it in 300000 light year ?

Now that we've established that we DO have such superposition in QM, and that it IS "real", let's tackle this annoying question brought up by the OP, who, BTW, never re-entered this thread after posting such a thing.

If an electron can exist everywhere simultaneously, then no particle accelerator in the universe can work, and neither can your electronics!

{Shock and confusion rings through the thread!}

"But ZapperZ! You just said that superposition is real, and so, doesn't this imply that you've just agreed that an electron can exist everywhere at the same time?"

And I will argue that in many instances, the electron can be describe as a classical particle and can easily be detected to be as that!

So what's the difference? One has to look at the scenario!

If I have a linear accelerator, let's say, and I created an electron at the gun at a certain time, I darn well have an electron that is NOT everywhere within the accelerator beamline! Why? Because I know well-enough when it is created and where! The very fact that I can detect it LATER down the beamline is the evidence. If it is everywhere all at once, I would detect it immediately at the end of the beamline. But I don't! So the insistence of an electron can exist everywhere is easily falsified by such an observation.

But why is this different than in the QM case?

If I have some way of generating an electron inside this beamline such that I have NO IDEA WHERE it will pop up at any given time (i.e. the only thing I know is that the probability of it appearing inside the walls of the beamline is zero), then NOW, I have a different situation/scenario than before. Now, the fact that I don't know when and where that electron will appear has changed the game entirely! The electron that appears in such a scenario can now be compared to, say, your infinite square well case in QM. You now have a QM case!

One cannot simply grab a QM principle, and then blindly apply it to every single scenario no matter how absurd it is. Leave such dubious practice to cranks who only learn about QM from pop-science sources.

Zz.

 

[ZapperZ]

How so?
I'd never heard about that, but I'll check it out.

Sure, but you haven't observed it either.

Define "observe".

I'm sorry, no need to get all up in arms about it. I was taking an unassuming position to respond to a guy who was obviously rambling because wether or not superposition is real it has nothing to do with the existence of reality. So take a chill pill.

Define "existence of reality". These are "mouthful" terms here. In physics, these things are well-defined. For example, the most recent results in looking for such "hidden variable" (which, btw, is quite related here) has found no such evidence. This means that the current version of quantum contextuality still holds true and has not been falsified!

https://www.physicsforums.com/showpost.php?p=4129344&postcount=155

Again, if you think that superposition isn't real after all of these numerous experiments and published papers, then I would love to hear you explain the physics of what they observed. And if you tell me that you've never heard them before (and it appears that you haven't), then you should not be so adamant in your argument that it isn't real because you obviously don't know enough do so!

Zz.

 

[Amok]

And if you tell me that you've never heard them before (and it appears that you haven't), then you should not adamant in your argument that it isn't real because you obviously don't know enough do so!

Honestly, I haven't heard of them. And I don't know what you mean by being "adamant", everyone is convinced of what they believe in until they aren't. And quite frankly, what you're defending is not exactly a widespread view (even if it might be correct), in fact if I google "Delft/Stony Brook SQUID experiments", the first hit I get is to a blog of yours and then to threads in these forums where you posted that stuff. And no one's ever heard or read everything there's to hear or read, so you can't really hold that against me.

Moreover, I didn't even say superposition isn't real ("adamant in your argument that it isn't real because you obviously don't know enough do so"), and it didn't really make any arguments for it. And I know that effects of superposition are visible, it's just I was never convinced that meant it was something real. And I'm sorry if I was wrong about, jeez...

So if you want to say something say it, but get off your high horse because no one likes arrogance.

You could've just posted a link to those articles and said "some scientists do think that superposition is real". And maybe explained it a bit.

Unfortunately I don't have access to journals right now, but I'll take a look those experiments when I do (next month).

 

[ZapperZ]

Honestly, I haven't heard of them. And I don't know what you mean by being "adamant", everyone is convinced of what they believe in until they aren't. And quite frankly, what you're defending is not exactly a widespread view (even if it might be correct), in fact if I google "Delft/Stony Brook SQUID experiments", the first hit I get is to a blog of yours and then to threads in these forums where you posted that stuff. And no one's ever heard or read everything there's to hear or read, so you can't really hold that against me.

Wait, it isn't widespread? In where?

Superposition is a central tenet of QM! How not widespread is this? In fact, it is the whole reason that quantum entanglement exists and is so strange! Without quantum entanglement, this is nothing more than a simple conservation of angular momentum problem that we find trivial in classical mechanics!

And if you look at those links I posted, the Delft/Stony Brook experiments were widely covered in science media when they appeared! And the publicity isn't even about superposition. It is about the SIZE of superposition! In other words, we have already accept superposition at the small scale, and now we are seeing it at the 10^11 particle scale! That's massive! That is what made the news!

Moreover, I didn't even say superposition isn't real ("adamant in your argument that it isn't real because you obviously don't know enough do so"), and it didn't really make any arguments for it. And I know that effects of superposition are visible, it's just I was never convinced that meant it was something real. And I'm sorry if I was wrong about, jeez...

So if you want to say something say it, but get off your high horse because no one likes arrogance.

And I will fully admit that I slapped you around a bit, because I'm seeing all of these arguments that are not supported by evidence. This is not science, and this is certainly not how physics is done. You cannot simply argue things based on tastes, or "beliefs". This isn't politics. If you do not know stuff well enough, then ASK! That is the strength of this forum, that we have such experts in many different fields. Learn from them! But if you start spewing all of these nonsense about a subject that some of us have had years of work in, then you are not only being insulting to us to think that you know enough to make such definite statements, but you are also being annoying!

So yes, from my point of view, you not only need to have some physics lessons of what we already know, but also an attitude adjustment on how you participate in this forum.

Zz.

 

[Amok]

And I will fully admit that I slapped you around a bit, because I'm seeing all of these arguments that are not supported by evidence. This is not science, and this is certainly not how physics is done. You cannot simply argue things based on tastes, or "beliefs". This isn't politics. If you do not know stuff well enough, then ASK!

How am I supposed to know I don't know my stuff well enough before someone shows it to me? What I learned is that when a system is in a superposition of states and you make a measurement on it, then it collapses into some eigenstate as we make our measurement (the textbook stuff). How is it possible to directly observe superposition in that case (and not just its effects, like interference patterns and such)? Can you concisely explain why you can (please, I am truly interested)?

That is the strength of this forum, that we have such experts in many different fields. Learn from them! But if you start spewing all of these nonsense about a subject that some of us have had years of work in, then you are not only being insulting to us to think that you know enough to make such definite statements, but you are also being annoying!

I didn't know you were an expert in this, I couldn't have known it, and I even if I did, argument for authority isn't the best. I didn't insult anyone directly or personally, I didn't mean to be insulting. If you felt insulted then you take these things way too personally, and that's really your problem, not mine.

but also an attitude adjustment on how you participate in this forum.

I have no problem admitting I was wrong, but no one needs to be arrogant or condescending about being right ("your assertions are silly", "you obviously haven't read enough to talk, but I have", "I'm an expert and I've made several posts about this already", "spewing all this nonsense", "this is not how science is done"). So if you think I'm wrong, just say it, and say why and that's it. Because if you really know all you say you do, you should be able to argue your position easily. If you don't feel like it, then refrain from posting.

And really, try not to take the things that I say that are wrong (or that you perceive as being wrong) as a personal insult against you. That really doesn't help a debate.

 

[Neandethal00]

I'm not sure, it sounds like some of the posters are saying
Wavefunctions are physical entities.
If yes, would anyone shine a little light on its physical nature?
I have been thinking all along wavefuntions are mathematical
models of 'environment' surrounding a particle.

 

[DrChinese]

I'm not sure, it sounds like some of the posters are saying
Wavefunctions are physical entities.
If yes, would anyone shine a little light on its physical nature?
I have been thinking all along wavefuntions are mathematical
models of 'environment' surrounding a particle.

The probability waves act AS IF they are real in and of themselves until collapse (whatever that actually is) occurs. So they can be manipulated (even split and recombined). That is in fact what happens with the double slit experiment.

So what starts off as a mathematical device also appears to have an element of reality itself. As ZapperZ and Drakkith have said, you see as "real" that which you set up the experiment to see.

 

[Drakkith]

Thanks Doc. You explain Quantums much better than I do!

 

[bohm2]

And if you look at those links I posted, the Delft/Stony Brook experiments were widely covered in science media when they appeared! And the publicity isn't even about superposition. It is about the SIZE of superposition!

I'm trying to understand this and I'm having some difficulty but is the superposition of macroscopic stuff like superconductivity analogous to quantum superposition on the microlevel? I'm asking because of this post by xepma and some other posts/links by deMystefier in this thread. Then again, I might be misunderstanding their arguments particularly because I haven't read the papers, yet:

The Psi in superconductivity is an order parameter of the system -- it's not the wavefunction of the electrons itself, even though it's frequently called that way. It's pretty easy to see that it can't be a wavefunction, since it has only one coordinate (hence it's not the wavefunction of a many-body system). The order parameter can be interpreted as the object responsible for breaking the U(1) symmetry. It therefore represents the charge density of the system (the absolute value of Psi) and the velocity field of the current (the phase term). The fact that charge is conserved automatically leads to the current equation you mentioned.

There is no reference to individual electrons.

The Ginzburg-Landau equation is an expression for the free energy of the system. The order parameter is treated as a classical object, and the non-linear Schrodinger equation follows from minimizing the free energy -- it is not based on the quantum-mechanical Schrodinger equation for the wavefunction (although you can derive it, strating from BCS theory).
In a Ginzburg-Landau approach there is absolute no reference to the underlying degrees of freedom carried by the electrons, i.e. the microscopics. It is solely phenomenological. You can derive this effective theory by starting from a quantum-mechanical treatment. A book such as Tinkham has treatments on that.

https://www.physicsforums.com/showthread.php?t=448366

Comparison of the Ahronov-Bohm effects in the two-slit interference experiment and in superconductor ring reveals fundamental difference between the Schrodinger wave function and the wave function describing macroscopic quantum phenomena.

http://xxx.lanl.gov/pdf/0812.4118v1.pdf

 

[Jazzdude]

I feel like he's trolling us. Repeating stuff he read somewhere else without understanding it.

Be careful with such statements. For what it's worth that statement would hold for you and others in this thread too. I've rarely read so many questionable and wrong statements stated with this much authority. And I'm not talking about the OP.

 

[tris_d]

No, all physical laws should describe the world we observe. If they describe differently, then either the laws are wrong or the world we observe isn't quite the idea we have of it.

We would like to describe the world we observe with certainty, but some of it we can not, so we use mathematical concepts that embed this uncertainty in the description. And this description is practical in a sense that it is useful, but it's not to be interpreted literally. While wave-particle duality is rather real, wave function is just abstract mathematical concept. Or so I would think.

 

[ZapperZ]

I'm trying to understand this and I'm having some difficulty but is the superposition of macroscopic stuff like superconductivity analogous to quantum superposition on the microlevel? I'm asking because of this post by xepma and some other posts/links by deMystefier in this thread. Then again, I might be misunderstanding their arguments particularly because I haven't read the papers, yet:

https://www.physicsforums.com/showthread.php?t=448366

http://xxx.lanl.gov/pdf/0812.4118v1.pdf

I would point out to you the Tony Leggett paper that I've referenced several times, and will reference here again:

A.J. Leggett "Testing the limits of quantum mechanics: motivation, state of play, prospects", J. Phys. Condens. Matt., v.14, p.415 (2002).

Note that no mater how you describe the supercurrent, there is a strong consensus that the entire supercurrent is describe by a single wavefunction, the same way 2 entangled particles are describe via one inseparable wavefunction. So this is ONE coherent entity even though it comprises of huge number of electrons. And that is all we need, and what is why Carver Mead stated that superconductivity is the clearest manifestation of quantum mechanics.

Zz.

 

[bhobba]

'doesn't address the issue of whether particles and reality exist at all times and esp. before detection.

QM does not answer that issue. What its wave nature is is waves of the representation of the system state when expanded in terms of position so its square gives the probability of being in that location if you observe it. A system state is the codification of what the outcome would be if you were to observe a quantum system, but what it is 'doing' or 'existing' when it is not being observed the theory is silent about. Different interpretations have a different take on it but since no experiment can tell the difference between them it is of little use in answering your question in any definite way. This is one of the essential aspects of QM that is responsible for much of its weirdness as well as misunderstandings. It is important though to understand what the issue really is rather than the (to use 'nice' language - if we were face to face I would say something more colorful) the half truths of some popular accounts.

Thanks
Bill

 

[bhobba]

The probability waves act AS IF they are real in and of themselves until collapse (whatever that actually is) occurs. So they can be manipulated (even split and recombined). That is in fact what happens with the double slit experiment.

So what starts off as a mathematical device also appears to have an element of reality itself. As ZapperZ and Drakkith have said, you see as "real" that which you set up the experiment to see.

I think 'appears' is a key word here - exactly as you indicate by 'AS IF'. I can find zero definite evidence it is any more than a codification of the knowledge about what the probability of the outcome of observations would be. This is the view of Ballentine in his book on QM. I know his ensemble interpretation is not everyone's but as far as I know no refutation of it exists.

Thank
Bill

 

[big_bounce]

Superposition waves just occur in a medium ?
Can two photons make a super position in vacuum ?

 

[bhobba]

Superposition waves just occur in a medium ?
Can two photons make a super position in vacuum ?

I have zero idea where you would get that from. The principle of superposition is a general principle having nothing to do with a medium:
http://en.wikipedia.org/wiki/Quantum_superposition

It actually follows from the definition of a state being a positive operator of unit trace but that's for a more advanced exposure to QM - the article above is a good start.

Thanks
Bill

 

[ZapperZ]

I think 'appears' is a key word here - exactly as you indicate by 'AS IF'. I can find zero definite evidence it is any more than a codification of the knowledge about what the probability of the outcome of observations would be. This is the view of Ballentine in his book on QM. I know his ensemble interpretation is not everyone's but as far as I know no refutation of it exists.

Thank
Bill

Then I suggest that you read this:

http://arxiv.org/abs/1111.3328

Zz.

 

[bhobba]

The hypothesis it is trying to refute 'is that the quantum state is a state of knowledge, representing uncertainty about the real physical state of the system'.

It is a state of knowledge all right but IMHO it does not represent 'uncertainy about the real physical state of the statem' because you first need to show it has a real physical state to be uncertain about. Got a proof for that?

Indeed the paper recognizes this: 'Nonetheless, this assumption, or some part of it, would be denied by instrumentalist approaches to quantum theory, wherein the quantum state is merely a calculational tool for making predictions concerning macroscopic measurement outcomes'.

This is precisely the view I take. A state can be viewed exactly as the ensemble interpretation espoused by Ballentine interprets it as - simply as a way of predicting the outcome of observations - the reality being the system and observational apparatus combined. Outside that, other than predicting the probabilities of what an observation would yield, a state, just like assigning probabilities to a coin, has no meaning. Probabilities do not represent elements of reality of something out there - neither do states - at least you can view it that way.

Thanks
Bill