What is the context of observation in this video?

[kaonyx]

Ahhhh! You see these inference rules of which thou spake are entirely a classical vanity! Allow me to illustrate.

I would like to discuss a specific example please, involving random numbers, because that is the challenge set to me by KenG. I will base this (very loosely) on the work done by The Irish physicist John Bell who famously demonstrated that Einstein's concern about the seriousness of the problem for physics, was fully justified.
If you have access to an Excel spreadsheet , type in this formula that should generate a random R or G, to represent a result of an experiment that is randomly green or red. (The F9 key forces a recalculate).
=IF(INT(RAND()*2)=0,"R","G"). I simply include this formula to illustrate the kind of data we are dealing with.
Ok now imagine we have a particle source located between two labs. An event in the source emits a two particles in opposite directions, into a detector located in each lab.
This particle causes two lights on each detector to light up randomly, much as our spreadsheet formula operates. (Two formulas for each detector).
Over lunch the physicists compare results. They get data sets like this:
R G<---*--->G R
G R<---*--->R R
R R<---*--->G G
R G<---*--->R G
G G<---*--->G R etc.
From the point of view of each lab, the results are random.
Here is a simple question for you.
Suppose that only after comparing these data sets side by side, over lunch, the physicists discover that there seems to be a rule operating between the labs.
It doesn't actually matter what the rule is, but let's make one up...
Suppose that the combination GG<---*--->RR is never observed.
And of course it is the same from each side, RR<---*--->GG is never observed.
What kind of theory can explain such a result?

The idea of the particle or the detectors passing signals between each other is ruled out because the experiment gives the same result when one of the detectors is on the moon and the other is on earth.

Maybe there is some kind of rule or formula or property that can be carried by the particle, that is like a computer program that can make a decision? But this idea falls flat, because it turns out that it doesn't matter which lab measures the properties first.
Now suppose that they also discover that not only is there no rule that can sent from the source, there is no POSSIBLE rule that can be sent from the source to account for the behaviour of the lights. This is very unsettling. (Some of the scientists go slightly insane and produce wacky theories about faster than light travel or telepathic alien jellyfish.) But the results withstand scrunity.

And now to make things worse, they conclude that the actions of the experimenters who detected properties in the lab, must pre-determine the lights in the lab that has not yet made the measurement. All of this done without any information or possible information transferred.
Quantum theory even goes a step further and says that the properties themselves are not "real" (ie clearly green or clearly red) until actually measured in the interaction with the detectors.

Finally now we can see how the role of the observer is implicated. Do you think that it is "mystical" and relies on the human mind? Or is this how things interact with each other, regardless of humans? Or does the reality we understand ultimately link to these spooky "entanglements" because of the "causal net" of "historical reality"?

 

[Ken G]

I definitely agree we construct the theories we understand, but what the theory is about is human-independent.

I think a lot of people believe that, but here's the problem: isn't the whole purpose of a theory to give us the ability to talk about whatever is the thing that the theory is about? So how can you separate the theory from what it's about? We just don't have any other access to what it's about. The map is not the territory, but everything that we can say about the territory is going to be some kind of map, including whether or not it is "human independent." So if we are in our theories, our maps, then we are also in what our theories are about. If you say the theory of gravity is about how things fall, then how do you know things fall? You know it because we perceive it, and build a theory about it, but we are just as much in the perception of the falling as we are in the theory that describes the falling. Physics is always done by physicists, there is no escape from that so we are better off building it right into our understanding of what we are doing from the get-go.

 

[StevieTNZ]

I think a lot of people believe that, but here's the problem: isn't the whole purpose of a theory to give us the ability to talk about whatever is the thing that the theory is about? So how can you separate the theory from what it's about? We just don't have any other access to what it's about. The map is not the territory, but everything that we can say about the territory is going to be some kind of map, including whether or not it is "human independent." So if we are in our theories, our maps, then we are also in what our theories are about. If you say the theory of gravity is about how things fall, then how do you know things fall? You know it because we perceive it, and build a theory about it, but we are just as much in the perception of the falling as we are in the theory that describes the falling. Physics is always done by physicists, there is no escape from that so we are better off building it right into our understanding of what we are doing from the get-go.

I would have to agree.

I remember seeing a Stephen Hawking video 10 or 15 years ago. There was an experiment involving baby chicks and electronic device (that looked like a mother hen). The experiment proved that the baby chicks intent affected the random nature of the electronic device involved in the experiment.

I'd be interested in seeing that video. Do you have a link to it?

 

[Ken G]

Maybe there is some kind of rule or formula or property that can be carried by the particle, that is like a computer program that can make a decision? But this idea falls flat, because it turns out that it doesn't matter which lab measures the properties first.

Actually, that doesn't fall flat in this example. To eliminate local realism, the Bell inequality gets quite subtle. If the rule is something simple like you never get RR with GG, that doesn't rule out that the particles carry the information with them (local realism). For example, if someone splits pairs of shoes and sends one to you and one to me, we know when we compare notes that we never get R with R or L with L, we only get R with L or L with R. This will also be true no matter which lab looks at the shoe first, or if it is on the Moon, and before the labs communicate they always see a random distribution of Ls and Rs. It is just a fact that is "carried with the shoes" that there is a determinate reality that says the two shoes are one L and one R even if we have no way of knowing which one we got until we look.

Quantum theory even goes a step further and says that the properties themselves are not "real" (ie clearly green or clearly red) until actually measured in the interaction with the detectors.

This is the problem, the ways in which QM requires this to hold is where the trouble appears, and gives us the need for an interpretation.

Finally now we can see how the role of the observer is implicated. Do you think that it is "mystical" and relies on the human mind? Or is this how things interact with each other, regardless of humans? Or does the reality we understand ultimately link to these spooky "entanglements" because of the "causal net" of "historical reality"?

Well, I certainly don't see anything "mystical" in noticing the involvement of the human mind. Without that involvement, quantum mechanics would in a very straightforward way predict the appearance of indefinite outcomes, not definite ones. That's the big issue in QM interpretation-- the theory doesn't "want" to make definite outcomes, it wants to make indefinite outcomes. But the human mind does not experience indefinite outcomes, so something has to give. That need for something to give is very much wrapped up in the involvement of the human mind, in the way that we perceive reality.

 

[kaonyx]

Ken G; You missed it. The shoes do not get split at the ***start*** they get split ***during*** their travel.

 

[kaonyx]

And if you don't understand that, I suggest you read up on "QBits". These are your shoes as a binary 0,1 mixed state. And that my friend is the whole basis of quantum computing.

 

[kaonyx]

The whole point of the Bell experiment was to demonstrate that the particles DO NOT individually carry information or rules with them about how to behave. And in fact that there is no rule, even in principle, that can cause one particle to behave in the required manner. You are arguing the case that Einstein tried to make, and he lost.
You can try to write down a little program that the particle can take with it, but somehow it also needs to take account of what happens to its mate, when it is still in flight. Well there is no such program and there cannot be. When one particle sets out, it still is NOT in one a particular state from its possible states.
This is the basis of quantum computing BTW. The 0,1 mixed state is called a qbit. It is Neither a 1 or a 0.
It is not in a particular state, and it does not carry, and cannot carry any rules to tell it what state to assume. There are no such rules even in principle.

 

[Kronos5253]

All the matters is whether my consciousness can collapse it.
I don't see any significance of forgetting a result. The wf still collapsed when I first observed it.

Whether the ten people observing have consciousness or not is not the sort of question I can verify. Well, in principle, I think it is a question I can answer. I don't see any importance of whether more than one person is conscious of the outcome or not.

Whether a fly or a monkey can collapse a wavefunction - all good questions. Let's see if they do collapse a wf. They may just well be able to have that ability.

Wouldn't it be easier to say that the field created by the electricity in our body, which increases when we think because of an increase in electrical activity in the brain, interacts with the particle, creating the wave to collapse?

Anything that we would have to use to make a measurement of the slit-experiment would do the same - i.e. a camera creates an electromagnetic field around it that would interact with the particle as well.

So wouldn't the wave function not collapse only when there is no interaction with it? Which, in my opinion, I can't see as ever being possible because there is always something to interact with, even inside of a vacuum.

EDIT: Excuse me if that's a dumb comment. I only have a general grasp.

 

[ThinkTanker]

It seems that most people are stating that the "observation effect" is just the "light" or whatever else changing the course of the particle, but that can't account for the results in the "delayed choice quantum eraser" experiment.

In that experiment the "measurement" was determined by where the electron ended up, which was randomly either known or unknown, yet it's entangled partner displayed wave distribution if unknown and particle distribution if known even though the determination of known/unknown is not observed until after the electron is measured to have been wave or particle.

No light interacted with the particle to cause wave collapse. It was the act of knowing the path that actually changed the outcome which seems to change an event in the past. http://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser#The_experiment".

 

[TGlad]

As far as I know, the delayed choice quantum eraser experiment is fully compliant with path integral quantum mechanics. There's nowhere in the article which suggests otherwise.

"It seems that most people are stating that the "observation effect" is just the "light" or whatever else changing the course of the particle"
Not just changing the course, but decohering and becoming entangled with a single instance of the probability wave, meaning the measuring device (and anything in some contact with it) becomes independent of the other instances of the wave, so we only see the single instance.

Regarding your last sentence, the article says this-
"Some have interpreted this result to mean that the delayed choice to observe or not observe the path of the idler photon will change the outcome of an event in the past. However, an interference pattern may only be observed after the idlers have been detected"

 

[Ken G]

Ken G; You missed it. The shoes do not get split at the ***start*** they get split ***during*** their travel.

I see no difference. You shake the cargo bay of an airplane **during** travel and some shoes fall out. Bell's theorem is much more subtle than the example you gave (it requires the qubit concept, not just any old rule for making widely separated lights go on in a correlated way).

 

[kaonyx]

The example I gave my friend was originally published in NewScientist magazine as exactly the way that Bell's theorem challenges common sense. If you like I can find the back issue for you to read.

 

[Ken G]

No what you said is certainly not how Bell's theorem challenges common sense. This is what you said:

Suppose that only after comparing these data sets side by side, over lunch, the physicists discover that there seems to be a rule operating between the labs.
It doesn't actually matter what the rule is, but let's make one up...

So no, it certainly does matte what the rule is. It has to be a rule of a very special kind, a correlation that is impossible in the "matching shoes" sense. It has to be a correlation that only comes up in wave mechanics, and only when noncommuting observations are done. It's very subtle indeed, and if New Scientist doesn't know that, at least we should.

 

[kaonyx]

It is very simple. A formula carried by a particle (eg. programmed into it is some way) (or that carries some kind of knowledge of its history) is an example of "hidden local variables".
One prediction of Quantum Mechanics is that the results between the two labs can be correlated (or anti-correlated - its much the same idea) in various surprising ways. (No the details don't matter here - if you really want you can look them up).

Bell's theorem states simply that there DO exist correlations that you can detect that CANNOT be explained by hidden local variables. These correlations are simple things, as I explained. They are not high tech magical things - and yes they can be reduced down to such mundane events as the colours of twinkling lights.

If a particle was programmed like a spreadsheet cell formula for example, then we can find simple correlations between the results of two labs that that could not be explained by any kind of formula or information or rule carried by each particle alone.
Even if we knew the formulas or rules or knowledge carried by both particles, it would not be enough.
So you see that not only is Bell's theorem extremely simple, it is extremely powerful in limiting what is knowable.

And incidentally Einstein relativity tells us that there is no "global spreadsheet in the sky" either, because that would require a preferred frame of reference or faster than light transfer of information. This latter idea might seem like an out, but actually it creates even worse paradoxes.

The relevance to observation here is of course that the experimenter, in the act of choosing where and when to determine the properties of one particle, has "acted without acting" in determining the properties of its twin.

 

[Ken G]

Yes, I can now agree with these corrected statements about Bell's result, except the last two sentences, which I can't judge because I don't know what they are saying. I would not say that any experimenter is determining the properties of the twin particles, as "determining" is often used to mean "influences" or "causes". I would say that the experimenter is gaining information about one particle by looking at the other. The nature of that information has surprising nonlocal characteristics (it isn't carried by the particle), but gaining information about one thing by looking at something else that has been coupled to it is not by itself anything so surprising.

 

[kaonyx]

You don't think so?

 

[ATOMS13]

How exactly do we exert energy on an electron by looking at it?

To observe an electron we have to use a microscope.. By using this microscope we exert energy..this energy, electrons, interact with what we are observing and there by "change" it