Double Slit Experiment

[Martyred Goat]

4 minutes ago, Mordred said:

I have a very high confidence that the possibility of a faster than light interaction is not the correct answer. Let me explain a few details not mentioned thus far. First off the entangled particles have already interacted with each other prior to being measured. They did so the instance they became entangled. This entanglement determines the probability of possible outcomes which is a correlation function ( another statistical term.) In the case of spin 1/2 particles such as electrons there is only two possible states spin up or spin down. However there is also a process called conservation of isospin and charge that is involved ( though all conservation laws apply in any particle interaction).

 This determines that the entangled pairs must be of opposite polarity. So when you measure one you automatically know the result of the other. The particles do not need to communicate or have any cause and effect at the time of the measurement. The initial interaction when they initially got entangled is sufficient.

That all sounds fine to me. The bit where my comprehension fails, Is when you measure one of the pair and it is spin up.... (i assume its a 50/50 chance) Then you somehow reverse time, measure again in the exact same way... and its now spin down. 

If this doesn't occur. i.e. you reverse time magically... Measure it as spin down... reverse time measure it as spin down (always getting spin down)... then it there is a factor that determined its state and so its not probabilistic. 

In terms of an example strange gave. 

"Well, the reason is that it is unstable and there are lower mass particles for it to decay into. But that isn't a cause. It is just a description of what is possible.

There is no clockwork mechanism that makes it decay after 2 us. There is nothing that causes it to decay at the exact time it does."

I produce a muon, it decays at a time. I reverse time (with my cool magic) And the muon decays at a slightly different time.... Now if the muon decays at the same time after reversing time (as i believe it would) then there was a mechanism that determined its time of decay. If reversing time does not reset and replay events in the same way... then i have to rethink a lot... as do many... 

Now i know reversing time is really not a good scientific test... but i'm running out of ways to articulate the issues i see. Would love a bit more info on the matter  

[Mordred]

No there is two detectors in the Bell experiment. when you measure one particle at spin up you know the other particle MUST be spin down. There is no time reversal involved. The muon decay is a different thread see my answer there 

Edited January 24, 2019 by Mordred

[Martyred Goat]

18 minutes ago, Mordred said:

No there is two detectors in the Bell experiment. when you measure one particle at spin up you know the other particle MUST be spin down. There is no time reversal involved. The muon decay is a different thread see my answer there 

I have no issues with the any of it. **Except** I fail to understand how bells theorem disproves determinism.. And don't think i have seen anything to suggest that anything is not potentially deterministic... I've learned a lot today (thank you all)...

But innocent until proven guilty... Till i know better... I will argue that events require causes! (And yes, i seem to have mashed the two topics a little) But i think i'm after the same knowledge in both. 

Off to the other thread i go. 

Edited January 24, 2019 by Martyred Goat

[Mordred]

Well using Bells theory to disprove determinism is more in line with a metaphysics argument. My experience with metaphysics is they tend to ignore the mathematics of any model they describe....

[Strange]

25 minutes ago, Martyred Goat said:

I produce a muon, it decays at a time. I reverse time (with my cool magic)

Once you leave the realms of science, you can invent any result you want. That has nothing to do with the real world.

5 minutes ago, Martyred Goat said:

 I fail to understand how bells theorem disproves determinism..

I don't think it does. 

Quantum theory is deterministic, in the sense it is not random: we can say what the possible outcomes are from any interaction. But we can only predict the probabilities of any outcomes, not that a specific one will occur.

 

[Mordred]

Once you measure something it is determined. The probabilities of superposition for example are predetermined probability states. QM as a theory tries to predict ALL possible outcomes and more specifically the likely hood of a given result. This makes QM a robust science as it can take into account a wide range of possible results. However this isn't unique to QM or QFT, even relativity involves probability in terms of possible particle spacetime paths to a certain degree.

 Needless to say statistical analysis is a vital part of any physics theory. It provides a greater range of predictability

Edited January 24, 2019 by Mordred

[Martyred Goat]

5 minutes ago, Strange said:

Once you leave the realms of science, you can invent any result you want. That has nothing to do with the real world.

I don't think it does. 

Quantum theory is deterministic, in the sense it is not random: we can say what the possible outcomes are from any interaction. But we can only predict the probabilities of any outcomes, not that a specific one will occur.

 

Aye!! Then we may be closer to the mistake i made (assuming i made one) 

So the outcome is pre determined, But our predictability is limited to probability of the outcome... We can't determine the specific outcome, but it is not "random" 

A muons decay... will occur at a specific time, but it is not predictable. So not random, but we are limited to predicting in terms of probability? 

For me, "true random" means that we restart the big bang, and the event occurs differently... Bells theorum disproving the possibility of hidden variables.. seemed to be saying that true random was present. 

Thanks for humouring me on all this. If nothing else, i have a shit tonne of reading material  

8 minutes ago, Mordred said:

Once you measure something it is determined. The probabilities of superposition for example are predetermined probability states. QM as a theory tries to predict ALL possible outcomes and more specifically the likely hood of a given result. This makes QM a robust science as it can take into account a wide range of possible results. However this isn't unique to QM or QFT, even relativity involves probability in terms of possible particle spacetime paths to a certain degree.

 Needless to say statistical analysis is a vital part of any physics theory. It provides a greater range of predictability

Ok. So just because it is not determined before it is measured... does not make it random... It just means that there is no way to know that it is not? 

 

[Mordred]

lets take the 2 microsecond decay rate this is actually just an average decay rate. That muon could take longer or decay quicker than the average.

A mean lifetime of a given particle is a statistical average. 

Edited January 24, 2019 by Mordred

[Strange]

16 minutes ago, Martyred Goat said:

A muons decay... will occur at a specific time, but it is not predictable. So not random, but we are limited to predicting in terms of probability?

It is random around that time.

It is deterministic in that we know it will decay and (with various probabilities) what it will decay into. It will not turn into two unicorns, for example.

18 minutes ago, Martyred Goat said:

For me, "true random" means that we restart the big bang, and the event occurs differently... Bells theorum disproving the possibility of hidden variables.. seemed to be saying that true random was present. 

It is very difficult to define what is meant by "random" and Bell's theory doesn't really tell us anything about that. It just tells us that there can't be factors that we don't know about which would explain the behaviour.

19 minutes ago, Martyred Goat said:

Ok. So just because it is not determined before it is measured... does not make it random... It just means that there is no way to know that it is not? 

If there is no way to predict when a specific muon will decay, and if the lifetimes are evenly distributed around a mean, then that is as good a definition of "random" as you are going to get.

 

[Mordred]

Here is the thread I mentioned you may find it useful

https://www.scienceforums.net/topic/106004-useful-fundamental-formulas-of-qft/

An easier visualization tool is to use a Feymann diagram the squiggly internal line is a VP oft called a field fluctuation. A VP is not an observable as per the link above. The external lines are observables or oft described as real particles though under QFT is a field excitation. 

[math]\array{e^+ \searrow &&\nearrow P^-\\&\leadsto &\\ e^-\nearrow &&\searrow P^+}[/math]

 

 

Edited January 25, 2019 by Mordred

[studiot]

On 1/24/2019 at 8:11 PM, Martyred Goat said:

 

I get that, I wish i had a grasp of calculus and a load of neat machines..... or even some polarisation filters!! (See if you can guess what i've been looking up)

I think faster than light interaction is a far more likely explanation than a probabilistic nature.... Gimme 10 years and i'll try and say why :/ 

 

 

I see it as a statement. aka "Event A will occur" 

 

 

Are you sure?

Probability is a funny beast.

You were also interested in the thread about quantum interpretations, and the important word is interpretation.

Interpretation of probability.

 

There are three types or interpretations of mathematical probability -- all different.

1) First we can assert that a probability of 1 means that event A has always happened and always will happen.

2) Second we can observe that event A has always happened but this cannot tell us what will happen next time.

An example of this would be the President of the United States has always been a man. So what is the probability that the next President will be a woman?

3) Third we can observe that event A has never happened, leading to two further interpretations.

'A' may not have happened because no trial has ever been made, but we have no reason to discount A, that is assign a probability of zero to it.
So we assign our best guess. Yes (informed) guess.

I might, for example, confidently assign the probability zero to the probability of Red Rum winning the 2019 Grand National.

 

An even more suprising result is the issue of how many trials are required for event A to happen if its probability is les than 1.

Suppose I want define event  A as as the number of cars that I must observe passing my drive before I spot a pink one.
That is the number of cars up to and including the first pink one.
I hope you agree that there are not many pink cars on the road so its probability will be low.

But however low this probability is the most likely number of cars to see the pink one is 1 (the first car).
The probability diminishes with each succesive number

That is the probability of it being the first is greater than the probability of it being the second is greater than the probability of it being the third and so on.

This suprising result demonstrates why it is best to be guided by the mathematics and not rely on common sense and intuition.
You have shown some good insights in your posts, but also some wildly wron ideas
Common sense and intuition can lead you far astray.

 

[Moreno]

(sorry I didn't reed the entire thread...)

But when particles (let say electrons) are observed doesn't it mean they are physically influenced? For example by photons if we use light to observe them? Can this physical influence by other particles be responsible for the change in their behavior?

 

 

[Mordred]

When it comes to the wave-functions and superposition absolutely, the very act of measurement collapses the superposition state.

[swansont]

27 minutes ago, Moreno said:

(sorry I didn't reed the entire thread...)

But when particles (let say electrons) are observed doesn't it mean they are physically influenced? For example by photons if we use light to observe them? Can this physical influence by other particles be responsible for the change in their behavior?

The physical influence is a separate effect from the collapse of the superposition. This sounds similar to the measurement effect being confused with the Heisenberg Uncertainty Principle.

[Moreno]

1 hour ago, swansont said:

The physical influence is a separate effect from the collapse of the superposition. This sounds similar to the measurement effect being confused with the Heisenberg Uncertainty Principle.

How exactly? Do you want to tell that when electrons are illuminated but unobserved their behavior doesn't change?

[swansont]

1 hour ago, Moreno said:

How exactly? Do you want to tell that when electrons are illuminated but unobserved their behavior doesn't change?

If I bounce a photon off of an electron, the electron recoils. That is a physical effect that changes its momentum (but is not an element of the HUP) but it is not necessarily part of the collapse of the superposition. The photon might not be involved in collapsing the superposition. As I said, these are not the same effects.

1 hour ago, Itoero said:

Those detectors  which are often used in a   Double Slit Experiment are measuring devices and collapse the superposition. This is the observer effect.

No, it's not.

The observer effect can happen to systems that are not in superposition (it's not even required that the experiment be probing QM). Thus, they cannot be the same. The loss of  interference in a double slit can be from the observer effect (e.g. which-path information), but they are not synonymous. You can get which-path information without detection.

But simply collapsing a wave function is going from an undetermined state to a determined one. That's a separate category. You can't say you changed the state of the system, since the system isn't in a determined state to begin with.