Does Observing a Particle in Superposition Entangle You With It?

[vanesch]

Yes, you are assuming that each time the experiment is performed, the hidden variable values of the photons leaving the source are randomly selected from the same distribution of hidden variable values. How then can you know that you are infact selecting the values in a random manner without actually knowing how the behaviour of the hidden variable.

This is exactly what you assume when you do "random sampling" of a population. Again, if you think that there are pre-determined correlations between measurement apparatus, or timing or whatever, then you are adopting some kind of super determinism, and you would be running in the kind of problems we've discussed before even with medical tests.

You still do not understand the fact that nobody has ever done this experiment the way you are assuming it. Nobody has ever taken steps to ensure that the distribution of the samples is uniform as you claim, mere repeatition multiple times is not enough as such an experiment system will be easily fooled by a time dependent hidden variable or a source in which the hidden variable value of the second photon pair emitted is related to the hidden variable value of the first photon pair emitted.

You can sample the photons randomly in time. You can even wait half an hour between each pair you want to observe, and throw away all the others. If you still assume that there is any correlation between the selected pairs, then this equivalent to superdeterminism.
That is like saying that there is a dependency between picking the first and the second patient that will get the drug, and between the first and the second patient that will get the placebo.

As I have pointed out already above, this assumption unnecessarily limits the hidden variable space, and has never been enforced in real Aspect type experiments. The critique stands!

You might maybe know that especially in the first Aspect experiments, the difficulty was the inefficiency of the setup, which made the experiment have a very low countrate. As such, the involved pairs of photons where separated by very long time intervals as compared to the lifetime of a photon in the apparatus (we talk here of factors 10^12).
There is really no reason (apart from superdeterminism or conspiracies) to assume that the second pair had anything to do with the first.

If you take 1000 persons and measure their height and weight exactly once each, it will tell you absolutely nothing about what you will obtain if you measure a single person 1000 times. If you find a correlation between weight and footsize in the 1000 measurements of the same individual, the ONLY correct inference is that you have a systematic error in your equipment. However if you find a correlation between weight and footsize in the 1000 measurements from different individuals, there are two possible inferences neither of which you can reasonably eliminate without further experimentation:
1- systematic error in equipment
2- Real relatioship between weight and footsize

Yes, but I was not talking about 1 person measuring 1000 times and 1000 persons measuring 1 time each, I was talking about measuring 1000 persons 1 time each, and then measuring 1000 OTHER persons 1 time each again.

You do realize that the 4 samples in an Aspect type experiment are taken "through one another" do you ?
You do a setting A, and you measure an element of sample 1
you do setting B and you measure an element of sample 2
you do a setting A again, and you measure the second element of sample 1
you do a setting D and you measure an element of sample 4
you do a setting C and you measure an element of sample 3
you do a setting A and you measure the third element of sample 1
you ...

by quickly changing the settings of the polarizers for each measurement.
And now you tell me that the first, third and sixth measurement are all "on the same element" ?

 

[ueit]

Vanesh,

I think that your require too much from a scientific theory. You require it to be true in some absolute sense.

In the case of the medical test in a superdeterministic universe, the theory that the medicine cured the patient is perfectly good from a practical stand point as it will always predict the correct result. The fact that, unknown by us, there is a different cause in the past does not render the theory useless. It is wrong, certainly, but probably not worse than all our present scientific theories.

Every physical theory to date, including QM and GR is wrong in an absolute sense but we still are able to make use of them.

 

[vanesch]

In the case of the medical test in a superdeterministic universe, the theory that the medicine cured the patient is perfectly good from a practical stand point as it will always predict the correct result. The fact that, unknown by us, there is a different cause in the past does not render the theory useless. It is wrong, certainly, but probably not worse than all our present scientific theories.

This is entirely correct, and is an attitude that goes with the "shut up and calculate" approach. Contrary to what you think - and if you read my posts then you should know this - I don't claim at all that our current theories are in any way "absolutely true". I only say that *if* one wants to make an ontology hypothesis (that means, IF one wants to pretend that they are true in some sense) then such and so, knowing that this is only some kind of game to play. But it is *useful* to play that game, for exactly the practical reason you give above.

Even if it is absolutely not true that taking a drug cures you, and that taking a drug only comes down to doing something that was planned long ago, and that the same cause is also making that you will get better, our pharmacists have a (in that case totally wrong) way of thinking how the drug is acting in the body and curing you, and they better stick to their wrong picture which helps them make "good drugs" (in the practical sense), than convince them that they don't understand anything about how drugs work in the human body, which would then render it impossible for them to design new drugs, given that their design procedures are based upon a totally wrong picture of reality.
So if nature "conspires" to make us think that drugs cure people (even if it is just a superdeterministic correlation), then it is practically seen, a good idea to devellop an ontological hypothesis in which people get cured by drugs.

It is in this light that I see MWI too: even if it is absolutely not true in an ontological sense, if nature conspires to make us think that the superposition principle is correct, then it is a good idea to devellop an ontological hypothesis in which this superposition principle is included. Whether this is "really true" or not: you will get a better intuition for quantum theory, in the same way the pharmacist will get a better feeling for the design of drugs based upon his wrong hypothesis that it are the drugs that cure the people.

 

[mn4j]

You can sample the photons randomly in time.

This CAN NOT be done, unless you know the time-behavior of the variables. You seem to be assuming that each variable has a single value with a simple normal distribution. What if the value of a variable changes like a cos(kw + at) function over time. If you don't know this before hand, there is no way you can determine by random sampling the exact behavior of the function. If you take "random" samples of this function, you end up with a rather flat distribution, which does not tell you anything about the behavior variable.

There is really no reason (apart from superdeterminism or conspiracies) to assume that the second pair had anything to do with the first.

On the contrary, the mere fact that they come from the same source gives me more than ample reason, no conspiracy. We are trying to find hidden variables here are we not? Therefore to make an arbitrary assumption without foundation that the emission of the first pair of photons does not change the source characteristics in a way that can affect the second pair is very unreasonable. No matter how long the time is between the emissions. Do you have any scientific reason to believe that hidden variables MUST not have that behavior?

Yes, but I was not talking about 1 person measuring 1000 times and 1000 persons measuring 1 time each, I was talking about measuring 1000 persons 1 time each, and then measuring 1000 OTHER persons 1 time each again.

Yes, and it does not change the fact that your results will tell you absolutely nothing about what you would obtain by measuring a single person 1000 times.

You do realize that the 4 samples in an Aspect type experiment are taken "through one another" do you ?
You do a setting A, and you measure an element of sample 1
you do setting B and you measure an element of sample 2
you do a setting A again, and you measure the second element of sample 1
you do a setting D and you measure an element of sample 4
you do a setting C and you measure an element of sample 3
you do a setting A and you measure the third element of sample 1
you ...

by quickly changing the settings of the polarizers for each measurement.
And now you tell me that the first, third and sixth measurement are all "on the same element" ?

No. I'm telling you that the results of this experiment can not and should not be compared with calculations based on measuring a single element multiple times. Your experiment will tell you about ensemble averages, but it will never tell you about the behavior of a single element.

 

[Count Iblis]

It may be more helpful to consider thought experiments for which (unitary, no fundamental collapse) quantum mechanics makes different predictions. I think that David Deutsch has given one such example involving an artificially intelligent observer implemented by a quantum computer. I don't remember the details of this thought experiment, though...

 

[vanesch]

This CAN NOT be done, unless you know the time-behavior of the variables. You seem to be assuming that each variable has a single value with a simple normal distribution.

I'm assuming that whatever is the time dependence of the variables, that this should not be correlated with the times of the measurement, and there is an easy way to establish that: change the sampling rates, sample at randomly generated times... If the expectation values are always the same, we can reasonably assume that there is no time correlation. Also if I have long times between the different elements of a sample, I can assume that there is no time coherence left.
I make no other assumption of the distribution of the hidden variables, than their stationnarity.

What if the value of a variable changes like a cos(kw + at) function over time. If you don't know this before hand, there is no way you can determine by random sampling the exact behavior of the function.

No, but I can determine the statistical distribution of the samples taken at random times of this function. I can hence assume that if I take random time samples, that I draw them from this distribution.

If you take "random" samples of this function, you end up with a rather flat distribution, which does not tell you anything about the behavior variable.

First of all, it won't be flat, it will be peaked at the sides. But no matter. That is sufficient. If I assume that the variable is "flatly" distributed in this way, that's good enough, because that is what this variable IS, when the sampletimes are incoherently related to the time function.

On the contrary, the mere fact that they come from the same source gives me more than ample reason, no conspiracy. We are trying to find hidden variables here are we not? Therefore to make an arbitrary assumption without foundation that the emission of the first pair of photons does not change the source characteristics in a way that can affect the second pair is very unreasonable.

That is not unreasonable at all, because the "second pair" will be in fact, the trillionth pair or something. In order for your assumption to hold, the first pair should influence EXACTLY THOSE pairs that we are going to decide to measure, maybe half an hour later, when we decided arbitrarily to change the settings of the polarizers exactly to the same settings.

It is then very strange that we never see any variation in the expectation values of any of the samples, no matter if we sample 1 microsecond later, or half an hour later, ... but that this change is EXACTLY what is needed to produce Bell-type correlations. This is nothing else but an assumption of superdeterminism or of conspiracy.

No matter how long the time is between the emissions. Do you have any scientific reason to believe that hidden variables MUST not have that behavior?

Well, as I said, that kind of behaviour is superdeterminism or conspiracy, which is by hypothesis not assumed in Bell's theorem, as he starts out from hidden variables that come from the same distribution for each individual trial, and the reason for that is the assumption (spelled out in the premisses of Bell's theorem) that the "free choice" is really a free, and hence statistically independent choice of the settings, and the assumption that the measurement apparatus is deterministically and in a stationary way giving the outcome as a function of the received hidden variable.

No. I'm telling you that the results of this experiment can not and should not be compared with calculations based on measuring a single element multiple times. Your experiment will tell you about ensemble averages, but it will never tell you about the behavior of a single element.

Sure. But the theorem is about ensemble averages of a stationary distribution. That's exactly what Bell's theorem tells us: that we cannot reproduce the correlations as ensemble averages of a single stationary distribution which deterministically produces all possible outcomes.

Assuming that the distributions are stationary, we are allowed to measure these correlations on different samples (drawn from the same distribution).

As such, the conclusion is that they cannot come from a stationary distribution. That's what's Bell's theorem tells us. Not more, not less.

So telling me that the distributions are NOT stationary, but are CORRELATED with the settings of the measurement apparatus (or equivalent, such as the sample times...), and that the measurements are not deterministic as a function of the elements of the distribution, is nothing else but denying one of the premisses of Bell's theorem. One shouldn't then be surprised to find other outcomes.

Only, if you assume that the choices are FREE and UNCORRELATED, you cannot make the above hypothesis.

It is well-known that making the above hypotheses (and hence making the assumption that the choices of the measurement apparatus settings and the actions of the measurement apparatus are somehow correlated) allows one to get EPR-type results. But it amounts to superdeterminism or conspiracy.

So you can now say that the Aspect results demonstrate superdeterminism or conspiracy. Fine. So ?