crowded quantum information

[joigus]

4 hours ago, bangstrom said:

That's what I said. If it matters to know which measurement came first, the experimenters can decide which to measure first.

 

There you go again. There is no "first." None of them comes first, and then the other. It'd better not.

That's why those people in Taiwan that you mentioned earlier are just measuring the speed of nothing. It is a non-speed.

That's why Ghideon's analogy is so brilliant. There's no speed at which the woman becomes a widow. Or it's infinite, whatever way you want to say it. It's a logical fitting between both ends. Nothing travels. No Cramer, I'm sorry.

It's the "speed" at which infinitely many propositions are anticorrelated, and infinitely many other propositions are totally non-correlated.

32 minutes ago, Ghideon said:

It could be interesting to probe the limits of the analogy and where it breaks down due to relativity and properties of QM if anyone is interested, but that may be a separate thread. 

I am. Let me give it a try. Let's introduce another Ghideon-observable: If I destroy their house while they're away, they "instantly" become homeless. In the classical world, It's possible to know whether a person is "widowed" and "homeless" at the same time. In QM those could be incompatible observables.

What's interesting in your analogy is that you've introduced a world of potentialities: Legal bindings, conditions, attachments, etc. This is, in the analogical space, playing the part of the wave function.

Edited November 17, 2022 by joigus
minor correction

[Eise]

1 hour ago, bangstrom said:

Information has no energy and a signal need not be energy bearing. The question is, if an electron on one end of an entanglement is found to be spin-up, how does it's former partner in the entanglement instantly 'know' it should be spin-down?

So your answer on my question of giving an example of a signal that does not imply transfer of energy is "No, I do not have such an example". Try again. And do not forget: no begging the question. Another example as entanglement.

1 hour ago, bangstrom said:

Simultaneous within the reference frame of the experiment itself and its measurements. Or, simultaneous relative to the origin of the entangled particles if you want to be really precise.

The detectors are ideally widely spaced so the events will never be simultaneous to all observers but that has no relevance to the experiment or its measurements since outside observations can not change the results.

Sigh. I nowhere said that results are changed because of 'outside observations' (I assume you mean 'observations by observers that move relative to the experiment'. Why are you so vague again and again?). I am saying, trying other words, there is no universally agreed timely order of the space-like separated measurements. The inertial frame of the experiment has no 'special authority': that would mean it would be a preferred inertial frame of reference, which is against SR. So different observers do not agree upon which measurement was first, and therefore about the direction of a signal.

[studiot]

On 11/15/2022 at 8:10 PM, Ghideon said:

Maybe not intended but I see this as yet an analogy for entanglement. Assume a couple is married and then separated by some (great) distance. When one (random) individual of the married couple dies we immediately know that the other party has become a widower or a widow. The immediate change from wife to widow (or husband to widower) does not need a signal.

I agree this is a superb example. 

Thank you +1.

1 hour ago, bangstrom said:

The question is, if an electron on one end of an entanglement is found to be spin-up, how does it's former partner in the entanglement instantly 'know' it should be spin-down?

It doesn't know, why should It ?

You have placed the germ of the answer in your use of 'former partner'.

Can you provide an actual example of the circumstances for these two electrons ?

[MigL]

11 hours ago, bangstrom said:

I have explained many, many times I understand this. What are you saying I don't understand?

I would think that you don't, because you say this ...

11 hours ago, bangstrom said:

That's what I said. If it matters to know which measurement came first, the experimenters can decide which to measure first.

How exactly do they decide, or synchronize if you will, without super-luminal communication ?
Please explain the process for space-like separated experiments/observations.

11 hours ago, bangstrom said:

an ordinary reference frame so your claim that I did had me confused.

A frame of reference is a frame of reference.
All are equally valid, and the term has a specific meaning.
That is obvious to all, as is your confusion.

11 hours ago, bangstrom said:

so there will always be a first measured.

Again, 'first' depends on your FoR.

11 hours ago, bangstrom said:

Different observers seeing signals going in different directions is a well understood phenomenon of SR.

No.
Different observers 'seeing' signals at different times ( ordering " is well understood phenomenon of SR.
But the actual signal ( if there was one ) could only go one way.
You cannot have different physical outcomes from frame dependent observations.

11 hours ago, bangstrom said:

Could it be that the common wave function that “defines” the correlation is a form of ‘signal’ that maintains correlation?

The common wave function is a mathematical relation of probability amplitudes.
Just as 2 +2 = 4 everywhere in the universe, the wave function is equally valid,  and the correlation is inherent to itsformulation..
Nothing has to be 'maintained'; it is, or it isn't.

[Ghideon]

8 hours ago, joigus said:

I am. Let me give it a try.

Thanks for your support, it helps my learning. 

8 hours ago, joigus said:

In the classical world, It's possible to know whether a person is "widowed" and "homeless" at the same time. In QM those could be incompatible observables.

This is an example where I need to do some more studying before commenting; I do not have enough knowledge about  incompatible observables in QM yet. But rest assured that I'll try to gain some insight and try to offer an opinion!

 

[bangstrom]

11 hours ago, joigus said:

There you go again. There is no "first." None of them comes first, and then the other. It'd better not.

There is rarely any need to know which measurement came first but it is possible to do so. One entangled particle goes to a detector on the left and another goes to the right. The experimenters can decide to move one detector closer to the source so that side becomes the first particle to be measured because the particle with the shortest distance to travel is the first to reach a detector. Easy-peasey.

 

12 hours ago, joigus said:

That's why Ghideon's analogy is so brilliant. There's no speed at which the woman becomes a widow. Or it's infinite, whatever way you want to say it. It's a logical fitting between both ends. Nothing travels. No Cramer, I'm sorry.

You are just giving a person or particle a different name. That is by no means entanglement.

[joigus]

4 minutes ago, bangstrom said:

There is rarely any need to know which measurement came first but it is possible to do so. One entangled particle goes to a detector on the left and another goes to the right. The experimenters can decide to move one detector closer to the source so that side becomes the first particle to be measured because the particle with the shortest distance to travel is the first to reach a detector. Easy-peasey.

 

1+1=0. Easy peasy.

Only problem is that's not true. If a person can't handle addition, any silly mistake they see as easy-peasy. It's easy for you because you've got the wrong picture.

An observer moving away from your "first" measurement at high-enough speed would see it happen later.

I took pains to make a drawing to explain it to you, but to no avail.

5 minutes ago, bangstrom said:

You are just giving a person or particle a different name. That is by no means entanglement.

Sure. "Madam, your husband died in an accident. You're a widow now, but don't worry. That's just a name we're giving you."

This person's life changes abruptly from there on, but she's none the wiser until the news come.

The problem is you don't even understand the dumbed-down example. And that's because you think you understand it and try to explain it to everybody else. I leave you with Bertrand Russell:

Quote

The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts.

Bertrand Russell

We're all here probably fools and fanatics ganging up on a wiser, enlightened mind.

2 hours ago, Ghideon said:

This is an example where I need to do some more studying before commenting; I do not have enough knowledge about  incompatible observables in QM yet. But rest assured that I'll try to gain some insight and try to offer an opinion!

This is the whole question of non-commutativity. Dirac introduced this interesting concept of q-numbers, as opposed to c-numbers, to highlight this idea, I think. C-numbers are the ordinary quantities of our classical, well-defined world. Q-numbers, on the contrary, are more like matrices. They do not commute. So they cannot be defined (diagonalised, perceived, spelled out, as numbers) at the same time = in the same basis of reference states. If you want to define one thing, you must un-define, or blur out, the other.

This concept takes quite a bit of getting used to, but I can assure you --if I understand QM at all, and I think I do to some extent--, it's the actuall crux of the matter. The idea that, when something is "defined," other things, other attributes, must become "undefined" or a superposition of possibilities.

[bangstrom]

2 hours ago, joigus said:

Only problem is that's not true. If a person can't handle addition, any silly mistake they see as easy-peasy. It's easy for you because you've got the wrong picture.

Apparently we have been discussing two different pictures.

I have been discussing the entanglement experiment the whole time and you appear to have been discussing an Alice and Bob scenario and that is a disconnect that appears to have lead to some major confusion.

To go back to the beginning, I said the first particle observed decides the quantum properties for both entangled particles.

Someone asked. “How do you know which particle was observed first?” A sensible question.

I said there is rarely a need to know which came first but the experimenters can decide which particle they choose to measure first.

That means they can choose to measure the particle that went to the left first- or- they can measure the particle that went to the right first. It all depends on how they setup the experiment prior to each run.

You said I know nothing about SR because I failed to consider the SR observations from outside observers. I explained that SR may work but it does not work across reference frames. SR can not change the order of events in the experiment so SR is irrelevant to the experiment and its calculations. The setup of the experiment itself decides the order of events.

I don’t know where Alice and Bob came from but that was never my view. Does that clarify things?

14 hours ago, Eise said:

The inertial frame of the experiment has no 'special authority': that would mean it would be a preferred inertial frame of reference, which is against SR. So different observers do not agree upon which measurement was first, and therefore about the direction of a signal.

A “preferred inertial frame of reference” has a specific meaning in physics (look it up) and it is prohibited by SR.

But nothing in SR prohibits designating your local frame as your center of discussion to the exclusion of all others.

7 hours ago, MigL said:

19 hours ago, bangstrom said:

That's what I said. If it matters to know which measurement came first, the experimenters can decide which to measure first.

How exactly do they decide, or synchronize if you will, without super-luminal communication ?
Please explain the process for space-like separated experiments/observations.

What I said is in reference to the experiment itself. The experimenters can decide which particle to measure first as part of the setup of the detectors in the experiment.

 

7 hours ago, MigL said:

Again, 'first' depends on your FoR.

My FoR was always the local RF of the experiment itself.

 

7 hours ago, MigL said:

But the actual signal ( if there was one ) could only go one way.
You cannot have different physical outcomes from frame dependent observations.

The signal (if there is one) is an important consideration. If there is one, it would likely be two, as with Cramer's or Wheeler-Feynman's advanced and retarded waves extending both forward and backward in time.

[Eise]

4 hours ago, bangstrom said:

I have been discussing the entanglement experiment the whole time and you appear to have been discussing an Alice and Bob scenario and that is a disconnect that appears to have lead to some major confusion.

So what is the difference between the entanglement experiment and the Alice and Bob scenario? 

4 hours ago, bangstrom said:

That means they can choose to measure the particle that went to the left first- or- they can measure the particle that went to the right first. It all depends on how they setup the experiment prior to each run.

You said I know nothing about SR because I failed to consider the SR observations from outside observers. I explained that SR may work but it does not work across reference frames

What? SR is the theory of how observers in different inertial frames of reference see physical events. It is the theory about how events are seen across different reference frames.

4 hours ago, bangstrom said:

SR can not change the order of events in the experiment so SR is irrelevant to the experiment and its calculations.

How often must I repeat this? No order of events is 'changed'. Observers in different inertial frames of reference just see them in different timely order, when events are space-like separated. So this is blatantly false:

4 hours ago, bangstrom said:

The setup of the experiment itself decides the order of events.

Again: the essential improvement of Aspect's experiment was that the measurements were space-like separated. And when the measurements are, then there will be inertial frames in which the timely order of the measurements is in one direction, and others where it is in the other direction.

4 hours ago, bangstrom said:

A “preferred inertial frame of reference” has a specific meaning in physics (look it up) and it is prohibited by SR.

And that is exactly what I am saying. However, you use the inertial frame of reference of the experiment as a preferred frame of reference. Which is prohibited by SR, exactly as you say.

 

Edited November 18, 2022 by Eise

[Eise]

And, oh, by the way, I am still waiting for an example:

20 hours ago, Eise said:

So your answer on my question of giving an example of a signal that does not imply transfer of energy is "No, I do not have such an example". Try again. And do not forget: no begging the question. Another example as entanglement.

 

[bangstrom]

1 hour ago, Eise said:

So what is the difference between the entanglement experiment and the Alice and Bob scenario? 

The entanglement experiment is grounded in the local reference frame of the experiment itself. The Alice and Bob scenario involves the SR observations of two outside observers. Their observations have no affect on the timing or calculations of the local reference frame and the experimental setup is blind to both classical and SR variations in timing by its perfectly symmetrical design so SR variations need not be considered.

1 hour ago, Eise said:

What? SR is the theory of how observers in different inertial frames of reference see physical events. It is the theory about how events are seen across different reference frames.

I agree, SR works differently in individual references frame so we can compare.

1 hour ago, Eise said:

How often must I repeat this? No order of events is 'changed'. Observers in different inertial frames of reference just see them in different timely order, when events are space-like separated. So this is blatantly false:

That is what I have been saying all along. Observations outside the local reference frame do not change the local reference frame.

[bangstrom]

1 hour ago, Eise said:

And that is exactly what I am saying. However, you use the inertial frame of reference of the experiment as a preferred frame of reference. Which is prohibited by SR, exactly as you say.

No, a 'preferred frame of reference' is an unworkable cosmological reference frame. That is the kind of "preferred" frame that is prohibited. It's an unfortunate and confusing use of the word 'preferred'.

 

1 hour ago, Eise said:

And, oh, by the way, I am still waiting for an example:

 This example should be non-controversial enough. https://newscenter.lbl.gov/2010/05/10/untangling-quantum-entanglement/

Previous experiments led by Graham Fleming, a physical chemist holding joint appointments with Berkeley Lab and UC Berkeley, pointed to quantum mechanical effects as the key to the ability of green plants, through photosynthesis, to almost instantaneously transfer solar energy from molecules in light harvesting complexes to molecules in electrochemical reaction centers. Now a new collaborative team that includes Fleming have identified entanglement as a natural feature of these quantum effects. When two quantum-sized particles, for example a pair of electrons, are “entangled,” any change to one will be instantly reflected in the other, no matter how far apart they might be. Though physically separated, the two particles act as a single entity.

[Eise]

1 hour ago, bangstrom said:

The entanglement experiment is grounded in the local reference frame of the experiment itself.

Again use of vague concepts. What does 'grounded' mean here? That the experiment happens to be done in an inertial frame?

1 hour ago, bangstrom said:

The Alice and Bob scenario involves the SR observations of two outside observers. Their observations have no affect on the timing or calculations of the local reference frame and the experimental setup is blind to both classical and SR variations in timing by its perfectly symmetrical design so SR variations need not be considered.

OK, obviously you need reading glasses. So in a large font, specially for you:

Nobody claims that observers that are in other inertial frames of reference affect the experiment.

The rest of your argument is BS. Observers in other inertial frames, like in Joigus' drawing, Carla and Daniel, see the space-like separated measurements, assuming they were simultaneous in the frame of reference of the experiment, in opposite timely order. Still they must agree on the physical interpretation of the measurements. A signal from one measurement to the other cannot fulfill this condition.

And, BTW, Alice and Bob are in the same inertial frame as the experiment. So what was the difference?

12 minutes ago, bangstrom said:

Now a new collaborative team that includes Fleming have identified entanglement as a natural feature of these quantum effects.

I said, an example without entanglement. Oh man...

12 minutes ago, bangstrom said:

No, a 'preferred frame of reference' is an unworkable cosmological reference frame. That is the kind of "preferred" frame that is prohibited. It's an unfortunate and confusing use of the word 'preferred'.

It is so simple. According to SR there is no preferred inertial frame of reference. But you take the FoR of the experiment as such. I think that is also the reason why you keep sticking to this stupid idea that we think that other observers somehow change the order of events. 

Edited November 18, 2022 by Eise

[joigus]

Eise also told you how the Clauser experiment is not, while the Aspect experiment is an Alice & Bob SR situation. You really should get your "stuff" together, Bangstrom.

I can't say a 100% you're just trolling around, because I must confess I've also considered --like Eise-- possible language barrier, circumstances I may not be aware of, etc. But this is getting ridiculous, and it does sound like you're just trolling around.

Edited November 18, 2022 by joigus
minor correction

[MigL]

The example Bangstrom presents is a non-starter in support of his claims ...

12 hours ago, bangstrom said:

One entangled particle goes to a detector on the left and another goes to the right. The experimenters can decide to move one detector closer to the source so that side becomes the first particle to be measured because the particle with the shortest distance to travel is the first to reach a detector.

If the experimenter can see ( or receive information from ) both right and left detectors, they are not space-like separated. 
And neither is the experimenter from either detector.
So there is no need for superluminal information transfer or signal.
Hence, no causality violations, and most importantly, no non-local effects are demonstrated.

Let us consider space-like separated events; experiments which would support your claims of non-locality.
Answer the question previously asked ...

17 hours ago, MigL said:

How exactly do they decide, or synchronize if you will, without super-luminal communication ?
Please explain the process for space-like separated experiments/observations.

You seem to be avoiding quite a few questions put to you, and just repeating the same things over and over again.

[joigus]

7 minutes ago, MigL said:

The example Bangstrom presents is a non-starter in support of his claims ...

If the experimenter can see ( or receive information from ) both right and left detectors, they are not space-like separated. 
And neither is the experimenter from either detector.
So there is no need for superluminal information transfer or signal.
Hence, no causality violations, and most importantly, no non-local effects are demonstrated.

Let us consider space-like separated events; experiments which would support your claims of non-locality.
Answer the question previously asked ...

You seem to be avoiding quite a few questions put to you, and just repeating the same things over and over again.

Yes. He really needs to read --with utmost attention-- Einstein's Gedanken on how two distant observers synchronise their clocks.

SR is not a nagging theoretical preconception that can be brushed aside for the purposes of doing your thing. It's the theory of how one attaches times and positions to events, and does it consistently. That's why we're beeing such "sticklers" about this.

Let's see if he finally understands this, because last time I looked he qualified it as "bickering."

[Ghideon]

14 hours ago, bangstrom said:

I don’t know where Alice and Bob came from but that was never my view.

Alice and Bob scenarios are very crucial to entanglement experiments. Alice and Bob are referenced (many times) in the 2022 nobel prize motivation, for instance in the section about Aspect** 

Quote

The Aspect experiments Like all theoretical results, Bell inequalities are derived under certain assumptions. One of these was of particular concern to Bell himself: the assumption that the two observers, Alice and Bob, make random choices of what to measure independent of each other. For this to be true, one must make sure that Alice cannot send a message to Bob about whether A1 or A2 is measured, which Bob receives before he decides to measure B1 or B2. In other words, Alice will not influence Bob’s choices. Assuming that special relativity is correct, this locality condition amounts to making sure that such a message would have to travel with a speed greater than that of light. There are also some other assumptions that we shall briefly discuss in a later section. Alain Aspect was the first to design an experiment that avoided the locality ‘loophole’

Note, when reading the above, that special relativity is of course correct according to current consensus / established theories.

Source: advanced-physicsprize2022-2.pdf (nobelprize.org) 
**) For instance mentioned a few pages ago by @Eise

[Ghideon]

22 hours ago, joigus said:

If you want to define one thing, you must un-define, or blur out, the other.

I agree that your example shows compatible observables. I’ll see if I understand compatible and incompatible by modifying your example slightly by using an observable “owner of exactly two pets” instead of the observable “homeless”:

Alice and Bob are married and together they own two pets, a cat Charlie and a dog Dave. Alice and Charlie travel together to a remote location. Bob and Dave stay together at home. Assume we are observers staying with Bob and Dave and we are allowed to observe one random event; the death of Bob or Dave. We have two possible outcomes:

1. Bob dies: This means the marriage ends; if Alice is alive she is now a widow and not married. But we do not know, and can’t know, if Alice owns exactly two pets. The observable “owner of exactly two pets” is “in superposition”* since we do not know if Charlie the cat is alive. 
2. Dave dies: This means that Bob’s marriage is in “superposition”; we do not know if he is a widower or a husband since we do not know if Alice is alive. But we know for sure that he does not own exactly two pets at this time. He can own one or zero, but not exactly two. If Alice is alive and well she is also is also affected she is now not "owner of exactly two pets". 

Some notes: There is no faster than light communication or signals. Special relativity seems to hold; Dave and Bob are close together in the same frame of reference. All observers, moving or not relative to Dave and Bob, will agree on who died first.

This is not necessarily a good analogy; main purpose if to test my understanding of compatible / incompatible observables. There are loopholes and limitations, feel free to reject or improve the analogy or my understating of incompatible observers. (I think I require some reading of the mathematics to understand this further.)

 

*) Not sure of the "superposition" is correct term here. Using "" since it is an analogy and not QM. 

[bangstrom]

19 hours ago, Eise said:

20 hours ago, bangstrom said:

The entanglement experiment is grounded in the local reference frame of the experiment itself.

Again use of vague concepts. What does 'grounded' mean here? That the experiment happens to be done in an inertial frame?

How is that statement vague? 'Grounded' in the local reference frame means it is based upon the local reference frame or it uses the local reference frame. And don't you have the same usage in German 'auf gegrundet'? 

 

19 hours ago, Eise said:

OK, obviously you need reading glasses. So in a large font, specially for you:

Nobody claims that observers that are in other inertial frames of reference affect the experiment.

That is a bit of confusion that kept things going. I kept saying that outside observations have no effect on the results of the experiment while "joigus" and others kept saying that outside observers see events in a different order so no one can say which came first. I was thinking of the experiment only while "joigus" and some others were discussing an Alice and Bob type scenario where SR matters.

That was an unfortunate confusion that never should have happened but it did.

 

19 hours ago, Eise said:

The rest of your argument is BS. Observers in other inertial frames, like in Joigus' drawing, Carla and Daniel, see the space-like separated measurements, assuming they were simultaneous in the frame of reference of the experiment, in opposite timely order. Still they must agree on the physical interpretation of the measurements. A signal from one measurement to the other cannot fulfill this condition.

My arguments were based on the experiment and the particles involved so I kept insisting that the SR differences of outside observers have no effect on the results.

 

19 hours ago, Eise said:

It is so simple. According to SR there is no preferred inertial frame of reference. But you take the FoR of the experiment as such. I think that is also the reason why you keep sticking to this stupid idea that we think that other observers somehow change the order of events. 

It is not so simple. For one thing, as I have explained before, you have the wrong idea about what a "preferred frame of reference" is and why it is prohibited by SR. Can you define what you mean by a preferred frame of reference?

Also consider this, if Alice is next to the detector on the far left and Bob is next to the detector on the far right and the entangled particles reach both detectors at measurably the same instant relative to their origin at the center. Alice will say the particle arrived at her detector first and Bob will say the particle arrived his detector first. This should indicate that they, like all outside observers, are not in exactly the same reference frame as the experiment itself so they are in no position to say which particle was detected first.

Others, and if I recall you are among them, say it is impossible to say which came first because the observation is relative. This is essentially saying outside observers can affect the order of events. I say there has to be a first by some tiny amount of time and the particles know which was observed first. It is not for outside observers to decide.

16 hours ago, MigL said:

If the experimenter can see ( or receive information from ) both right and left detectors, they are not space-like separated. 

Yes, the detectors are space-like separated even if they are both visible.  If they are beyond the range of a light signal, they are light-like separated.

See the definitions from physics.stackexchange.com/questions below.

Spacelike separation means that there exists a reference frame where the two events occur simultaneously, but in different places.

Timelike separation means that there exists a reference frame where the two events occur at the same place, but at different times.

Lightlike means that, well, light could travel between those points.

 

16 hours ago, MigL said:

On 11/17/2022 at 1:49 PM, MigL said:

How exactly do they decide, or synchronize if you will, without super-luminal communication ?
Please explain the process for space-like separated experiments/observations.

You seem to be avoiding quite a few questions put to you, and just repeating the same things over and over again.

 

Your question was strange but I did answer it. The detectors may be space-like separated but they are not light-like separated for the operators so nothing superluminal was required.

The detectors are only light-like separated when the signal between them is superluminal. There are ways of changing the detectors at superluminal speeds like for experiments involving Wheeler’s delayed choice but that was not one of them.

If anyone thinks I didn’t answer their question their response should be- as was yours, ‘You didn’t my question about...’ And if they didn’t like my answer they should explain why and not just repeat the same question expecting a different answer. That would save a lot of miscommunication. And don't complain, 'You didn't answer my question,' without explaining what it was and expect me to guess.

 

Edited November 19, 2022 by bangstrom
Deleted a redundant paragraph

[Lorentz Jr]

On 10/21/2022 at 6:55 PM, bangstrom said:

The three Nobel prize winners won their laurels for demonstrating the reality of non-locality- aka "spooky action at a distance".

On 10/21/2022 at 8:49 PM, MigL said:

No, they did not demonstrate the 'reality of non-locality'.
They demonstrated the absence of local realism.

Didn't Hensen's 2015 experiment* show that the state of Bob's electron is correlated with the final state of Alice's electron after she measures two mutually non-commuting properties (spin states along different axes), even though (a) the state of Bob's electron must have been correlated with the intermediate state of Alice's electron between the two measurements she made, and (b) the final measurements were separated by spacelike intervals? I'm struggling to fit that into the socks-and-widows analogy.

 

* Nature volume 526, pages 682–686, Loophole-free Bell inequality violation using electron spins separated by 1.3 kilometres

 

Edited November 19, 2022 by Lorentz Jr

[bangstrom]

On 11/17/2022 at 7:12 AM, studiot said:

On 11/15/2022 at 2:10 PM, Ghideon said:

Maybe not intended but I see this as yet an analogy for entanglement. Assume a couple is married and then separated by some (great) distance. When one (random) individual of the married couple dies we immediately know that the other party has become a widower or a widow. The immediate change from wife to widow (or husband to widower) does not need a signal.

I agree this is a superb example. 

That was the worst explanation of entanglement I have ever seen. If that is entanglement, then Aspect and Clauser got the Nobel for discovering that entanglement is a matter of changing the names on particles.

On 11/17/2022 at 7:12 AM, studiot said:

On 11/17/2022 at 5:16 AM, bangstrom said:

The question is, if an electron on one end of an entanglement is found to be spin-up, how does it's former partner in the entanglement instantly 'know' it should be spin-down?

It doesn't know, why should It ?

The quantum properties of both entangled particles are random and changing on both ends of the entanglement until one property of the two is measured. The particles can be widely separated, and because of the distance between them, one particle shouldn’t ‘know’ what is happening to its partner without some form of communication between them and time for the communication to reach it.

On 11/17/2022 at 7:12 AM, studiot said:

Can you provide an actual example of the circumstances for these two electrons ?

If a pair of entangled electrons is generated and a one sent in one direction and the other is sent in another direction the measurement of a single property of one electron, the spin direction for example, instantly establishes the identity of both separated electrons and quantum properties of the two will be found to be anti-correlated. Even if the the electrons are far apart and before a light signal has time to reach the second electron to get the message and ‘know’ which property was observed and how it should be oriented.

https://www.tudelft.nl/en/dossiers/loophole-free-bell-test-tu-delft-crowns-80-years-old-debate-on-nature-of-reality-einsteins-spooky-action-is-real

“Quantum mechanics states that a particle such as an electron can be in two different states at the same time, and even in two different places, as long as it is not observed. This is called ‘superposition’ and it is a very counter-intuitive concept”, says lead scientist Professor Ronald Hanson. Hanson’s group works with trapped electrons, which have a tiny magnetic effect known as a “spin” that can be pointing up, or down, or - when in superposition - up and down at the same time. “Things get really interesting when two electrons become entangled. Both are then up and down at the same time, but when observed one will always be down and the other one up. They are perfectly correlated, when you observe one, the other one will always be opposite. That effect is instantaneous, even if the other electron is in a rocket at the other end of the galaxy”, says Hanson. 

 

[Eise]

4 hours ago, bangstrom said:

How is that statement vague? 'Grounded' in the local reference frame means it is based upon the local reference frame or it uses the local reference frame.

So you mean the entanglement source and the detectors are in same inertial reference frame, in other words, they are at rest relative to each other? Then say so.

1. Next step: is this a preferred frame of reference? A preferred frame of reference in this context would mean that only in this frame correct conclusions about what physically is happening can be drawn.
2. Next step: according to SR there are no preferred inertial frames of reference. Still, all observers, whatever their speed and direction, agree on the physics about what is going on. (However they can differ on distances, durations, timely order of events, simultaneity etc.) That is against 1., so 1. does not apply: the inertial frame of the experiment is not a preferred frame of reference.
3. Next step: if there is a physical signal from one measurement to the other, all inertial observers should agree on this signal, especially its direction.
4. Next step: for some observers Alice's measurement was first (e.g. Daniel in Joigus' drawing), for others Bob's measurement was first (Carla).
5. Next step: Daniel and Carla do not agree on the direction of a hypothesised signal. But as they, according to SR, should agree on the physics of the situation (in this case which measurement determines the other), there can be no signal.

As you see, there is no influence whatever from the different observers.

4 hours ago, bangstrom said:

That is a bit of confusion that kept things going. I kept saying that outside observations have no effect on the results of the experiment while "joigus" and others kept saying that outside observers see events in a different order so no one can say which came first.

Italics: Nope. Every observer observes the measurements, but they do not agree with each other which was first. So there is no objective first. Just to be sure: that is only true when the measurements are space-like separated, in the SR meaning of that concept. Not just space separated. Which you are using in your next argument:

4 hours ago, bangstrom said:

Also consider this, if Alice is next to the detector on the far left and Bob is next to the detector on the far right and the entangled particles reach both detectors at measurably the same instant relative to their origin at the center. Alice will say the particle arrived at her detector first and Bob will say the particle arrived his detector first. This should indicate that they, like all outside observers, are not in exactly the same reference frame as the experiment itself so they are in no position to say which particle was detected first.

Oh my! In SR we talk about inertial frames of reference, not about the position of observers in space! It is 'easy-peasy' for Alice, if she knows the distance to Bob's detector, to conclude that his measurement was at the same time as her measurement. If detectors and entanglement source are in the same inertial frame of reference, Alice and Bob can agree on which measurement was first (or if they were simultaneous). Obfuscation from your side again: you have changed the meaning of 'reference frame'. Or you have a total misunderstanding of SR. Or both.

4 hours ago, bangstrom said:

Others, and if I recall you are among them, say it is impossible to say which came first because the observation is relative. This is essentially saying outside observers can affect the order of events.

Nope. I say that for space-like separated events there is no objective order of events. And just observing does not change anything. Do  you really think we are saying that Carla and Daniel change the 'objective' order events, and that in different directions?

Edited November 19, 2022 by Eise

[studiot]

27 minutes ago, Eise said:

So you mean the entanglement source and the detectors are in same inertial reference frame, in other words, they are at rest relative to each other? Then say so.

Don't you think this statement is a little to tight ?

Bodies can be in the same inertial frame so long as they are not accelerating relative to each other.

Quote

https://en.wikipedia.org/wiki/Inertial_frame_of_reference

In classical physics and special relativity, an inertial frame of reference (also called inertial reference frame, inertial frame, inertial space, or Galilean reference frame) is a frame of reference that is not undergoing any acceleration. It is a frame in which an isolated physical object — an object with zero net force acting on it — is perceived to move with a constant velocity (it might be a zero velocity) or, equivalently, it is a frame of reference in which Newton's first law of motion holds. ^[1] All inertial frames are in a state of constant, rectilinear motion with respect to one another; in other words, an accelerometer moving with any of them would detect zero acceleration.

 

[Eise]

1 minute ago, studiot said:

Bodies can be in the same inertial frame so long as they are not accelerating relative to each other.

Nope. An observer with a constant velocity compared to a defined inertial frame will observe distances, durations etc differently from an observer in that defined inertial frame. What is true is that when we have an inertial frame of reference, and an observer is moving with constant velocity relative to that inertial frame, then that observer is also in an inertial frame. But it is another one.

[studiot]

1 hour ago, bangstrom said:

That was the worst explanation of entanglement I have ever seen. If that is entanglement, then Aspect and Clauser got the Nobel for discovering that entanglement is a matter of changing the names on particles.

Thank you for replying to my recent comments.

I started a thread just for you and for Hoola since he seems to have been forced out of this thread and started a new one again. Have you seen it ?

You need to understand that entanglement, superposition mechanics and many other phenmomena were studied long before any quantum theory arose. In many cases quantum entanglemen can be different from classical entanglement, which @Ghideon example is. This is also the case with the example of the socks or the gloves. But they have a characteristic in common with quantum entanglement, notably that the actual states of both particles are set at the instant of entanglement. Some information is also encoded in the entanglement at that instant.

The entangled objects do not suddenly or randomly switch their entangled characteristics when one is determined.
Further the randomness is not in the entanglement but in this knowledge of this information.

1 hour ago, bangstrom said:

The quantum properties of both entangled particles are random and changing on both ends of the entanglement until one property of the two is measured. The particles can be widely separated, and because of the distance between them, one particle shouldn’t ‘know’ what is happening to its partner without some form of communication between them and time for the communication to reach it.

Quite right not only shouldn't it know, it just doesn't.

1 hour ago, bangstrom said:

If a pair of entangled electrons is generated and a one sent in one direction and the other is sent in another direction the measurement of a single property of one electron, the spin direction for example, instantly establishes the identity of both separated electrons and quantum properties of the two will be found to be anti-correlated. Even if the the electrons are far apart and before a light signal has time to reach the second electron to get the message and ‘know’ which property was observed and how it should be oriented.

Once again thank you for attempting to reply, but you haven't answered the question.

You need first to describe where and how these two electrons become entangled, and then most importantly how you separatethem without interacting with them, bearing in mind that any interaction is an observation that automatically breaks the entanglement.

14 minutes ago, Eise said:

Nope. An observer with a constant velocity compared to a defined inertial frame will observe distances, durations etc differently from an observer in that defined inertial frame. What is true is that when we have an inertial frame of reference, and an observer is moving with constant velocity relative to that inertial frame, then that observer is also in an inertial frame. But it is another one.

The whole point of SR is that you measure or calculate everything in the same inertial frame, which you are at liberty to pick.

That is what the Lorenz transformations are all about.