Physicists at ANU Experimentally Conclude (again) That Physical Reality Exists Only When Observed

Paul C. Anagnostopoulos

Nap, interrupted.
Member
#21
Paul,
You have left out the word "simultaneously" in your response and it is a critical aspect of the concept.

I am no expert in this area, however in sequential measurements, I believe enough mutual information can be gained to obtain a good idea of the state of a particle. Remember that mutual information can be collected, in an historical account. A physical measurement (and hence, physical information) is in the "here and now". An accounting of a SoA (state of affairs) allows the compounding of information. The immediate past and future -- speak to the state of affairs.
I agree that simultaneity is important. I don't know what "mutual information" is.

~~ Paul
 
#22
Paul,
You have left out the word "simultaneously" in your response and it is a critical aspect of the concept.

I am no expert in this area, however in sequential measurements, I believe enough mutual information can be gained to obtain a good idea of the state of a particle. Remember that mutual information can be collected, in an historical account. A physical measurement (and hence, physical information) is in the "here and now". An accounting of a SoA (state of affairs) allows the compounding of information. The immediate past and future -- speak to the state of affairs.

I am open to correction in this matter and encourage better knowledge to set me aright.
As Paul said, you can't know both the position and momentum of a particle.

Each measurement is also independent.
 
#24
Interesting that there's now discourse about the uncertainty principle although that doesn't have much to do with topic of the thread.
Stephen seemed to imply that he could say something about both the position and momentum of 'a' particle whilst it is between measurements.

Which is exactly the Issue your OP was addressing... wasn't it?
 
#26
Stephen seemed to imply that he could say something about both the position and momentum of 'a' particle whilst it is between measurements.

Which is exactly the Issue your OP was addressing... wasn't it?
Only in part. You mentioned that each measurement is independent. This is what is expected under realism. But this is not the case, it is dependant on the experimenters choice on how to measure, even after the particles journey. Hence delayed choice experiment.

The extraction of information by choice actualises it into reality from potential. Quantum cryptography is a functional working example.
I would say it is more about knowing than observing.
 
#27
Only in part. You mentioned that each measurement is independent. This is what is expected under realism. But this is not the case, it is dependant on the experimenters choice on how to measure, even after the particles journey. Hence delayed choice experiment.

The extraction of information by choice actualises it into reality from potential. Quantum cryptography is a functional working example.
I would say it is more about knowing than observing.
What isn't the case?
 
#28
What isn't the case?
That the properties are independent. I realise that you were talking of the choice of position or momentum. Not that you are wrong.
Just a semantic issue, because the basis of the OP is that of the delayed choice experiment.
So no, it is not exaclly the issue the OP is addressing but is in part. The other part being dependant on what, how to measure even after the fact.
 
#29
That the properties are independent. I realise that you were talking of the choice of position or momentum. Not that you are wrong.
Just a semantic issue, because the basis of the OP is that of the delayed choice experiment.
So no, it is not exaclly the issue the OP is addressing but is in part. The other part being dependant on what, how to measure even after the fact.

I was meaning independent in that each measurement stands on its own, i.e. You measure, (or you don't) but you can't measure the same particle again and learn something new about the first measurement.

As for what you thought I was meaning... I'm afraid experimenters can't influence the results of QM measurements. At present it's accepted that no matter where you are, or who you are, you will get the same results as any body else. If experimenters got different results because they were influencing the measurement, QM wouldn't be as accurate as it is.

Stephen's next post then seemed to imply that he could say something about both the position and momentum (state) of 'a' particle whilst it is between measurements. Which sounds rather like the modern idea of 'weak measurement'.

Not only can he... not say anything about both the position and momentum of a particle. He cannot say anything about a particle when it is between measurements.

That we can't get rid of the experimenters choice of what to measure is significant, but this doesn't affect any of my earlier points about the measurement of a particle.

Rather I think that you are confusing our observations of the base 'process' - which I'm talking about - with how we get to the 'output' i.e. bring it into space-time
 
#30
Max. No you are confused about what I am talking about. I even mentioned I knew the distinction you were making and said you were not wrong. What is up with comprehension here?

I was mainly adressing this point...

"Is exactly what the OP is addressing wasn't It?"

I said in only part, because it relates to the delayed choice experiment. That the properties are not independant. Different to what you said that the measurements are independant. Yes I know. As I said. I can say it again if you like?

What exactly am I confused about Max?

It seems you are confused. Choice is the factor, it is a delayed choice experiment! the choice of what and how to measure can... if you believe the particle took a particular path, (realism) then choices of measurement are effecting the past! I don't know what you are on about really. It does affect your point directly. My post was very simple, sorry If I hurt your ego, I did not think it was a big deal.

Seriously I wonder why I post sometimes. Why ask a question if you don't want it answered?

BTW I can't speak for Stephen but I got no such thing from his post. The term sequential measurement should be enough to distinguish. An assumption on your part perhaps? I could be wrong. That is up to Stephen.

Actually it is dependant on how much information you extract. As you mention, weak measurement. Once again, about knowing. So no it is not independant, it depends on much of one you measure.

But a new experiment has managed to circumvent this rule—the so-called uncertainty principle—by ascertaining just a little bit about a particle’s position, thus retaining the ability to measure its momentum, too.
http://www.scientificamerican.com/article/particle-measurement-sidesteps-the-uncertainty-principle/
 
#31
Max. No you are confused about what I am talking about. I even mentioned I knew the distinction you were making and said you were not wrong. What is up with comprehension here?

I was mainly adressing this point...

"Is exactly what the OP is addressing wasn't It?"

I said in only part, because it relates to the delayed choice experiment. That the properties are not independant. Different to what you said that the measurements are independant. Yes I know. As I said. I can say it again if you like?

What exactly am I confused about Max?

It seems you are confused. Choice is the factor, it is a delayed choice experiment! the choice of what and how to measure can... if you believe the particle took a particular path, (realism) then choices of measurement are effecting the past! I don't know what you are on about really. It does affect your point directly. My post was very simple, sorry If I hurt your ego, I did not think it was a big deal.

Seriously I wonder why I post sometimes. Why ask a question if you don't want it answered?

BTW I can't speak for Stephen but I got no such thing from his post. The term sequential measurement should be enough to distinguish. An assumption on your part perhaps? I could be wrong. That is up to Stephen.

Actually it is dependant on how much information you extract. As you mention, weak measurement. Once again, about knowing. So no it is not independant, it depends on much of one you measure.



http://www.scientificamerican.com/article/particle-measurement-sidesteps-the-uncertainty-principle/
Yeah, if you can talk about 'weak measurement' in that way, it just confirms how far away we are from each other's position with regards to our respective understanding of QM.
 
#32
Yeah, if you can talk about 'weak measurement' in that way, it just confirms how far away we are from each other's position with regards to our respective understanding of QM.
I suppose so.
All I said was it depends on how much information you extract. it is amazing how you reach such conclusions from a few general words.

How you say the experimenters can't influence the result, that the result is implicit no matter what, I have no idea.

This directly contradicts what the OP is about!
According to that logic the properties are existing independently. That is realism.

But yeah obviously I don't know what I am talking about.
 
#33
I suppose so.
All I said was it depends on how much information you extract. it is amazing how you reach such conclusions from a few general words.

How you say the experimenters can't influence the result, that the result is implicit no matter what, I have no idea.

This directly contradicts what the OP is about!
According to that logic the properties are existing independently. That is realism.

But yeah obviously I don't know what I am talking about.
I'd agree that you don't understand what I've been talking about.
 
#34
Well you would be wrong about that too.

It is the fact you can't measure both position and momemtum (precisely) simultaneously. Right? A well known phenomena.

They actually do not even have precise values simultaneously. The operators for postion and momentum are not commutable.

So to answer your question again in simple format. No it is not THE Issue.

Keep your pissing contests, not interested.
 
#35
This is the issue. The significance of the OP is that it has essentially been done with helium atoms instead of photons.

"Thus one decides the photon shall have come by one route or by both routes after it has already done its travel". J A Wheeler.
 
#36
Well you would be wrong about that too.

It is the fact you can't measure both position and momemtum (precisely) simultaneously. Right? A well known phenomena.

They actually do not even have precise values simultaneously. The operators for postion and momentum are not commutable.

So to answer your question again in simple format. No it is not THE Issue.

Keep your pissing contests, not interested.
We've already established that you don't undestand what I've said... You said it yourself...
 
#37
Which is exactly the Issue your OP was addressing... wasn't it?
No. Though there's some overlap between everything QM, the "observer effect" is a different concept to the uncertainty principle. In the OP ("observer effect") the particle has neither position nor momentum when not observed - it simply doesn't exist. The uncertainty principle states that, when observed, one cannot know both the momentum and position of the now existent particle simultaneously.
 
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#39
No. Though there's some overlap between everything QM, the "observer effect" is a different concept to the uncertainty principle. In the OP ("observer effect") the particle has neither position nor momentum when not observed - it simply doesn't exist. The uncertainty principle states that, when observed, one cannot know both the momentum and position of the now existent particle simultaneously.
Stephen appeared to claim that he could learn the momentum and position (state) of a particle from consecutive measurements... so yeah, what I said is exactly about the OP.
 
#40
Actually the fact you cannot know both momentum and position is not at all strange.

In order to get a position you have to hit the particle with a light wave. This knocks some of the momentum off. If you use a lower frequency you will not affect momentum much but because of the longer wave length you won't have as much accuracy of position. A higher frequency will give more accuracy but disrupt momentum to a much higher degree.

It is actually not that strange at all, and it is not the point.
 
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