This post is regarding the famous experiment with a stream of electrons being shot into a double-slit (http://www.youtube.com/watch?v=DfPeprQ7oGc). This experiment produces an interference pattern on the screen.

If the experiment is changed so that only a single electron is shot at a time, an interference pattern is still seen. The electron "splits" into two "ghosts" which interfere with each other.

Now, if an observer is placed at the point just before single electrons enter the double slits, the observer will see the electron clearly entering either of the slits. In other words, the act of "observing" collapses the wave function. The interference pattern is no longer seen; only a pattern of two distinct strips of electrons can be seen.

My question is this, as "consciousness" can collapse the wave function, can this experiment be used as a test for "consciousness"? eg. If I were to repeat this experiment with a robot instead of a human observing single electrons entering either of the slit, would I see a final interference pattern on the screen as the non-conscious robot cannot collapse the wave function?

Similarly, if a dog was the observer, would I see a final two strips after the experiment is finished? (and would this prove that the dog has a "consciousness").

I am sure I have misunderstood something fundamental about quantum mechanics. After all, if my hypothesis is true, this would prove the existence of the soul once and all.

How would the observation itself take place? To "see" the electrons there has to be some form of interaction, bombardment with fotons for example, and that would alter the experiment. It´s the observation itself that collapses the wave function, as much as I understand. The results of the observations could be stored, no one ever seeing it. Consciousness or not shouldn´t be a primary issue.

No.

It is not the act of a consciousness perceiving the electron that causes the change in its behavior. In order to perceive the electron you have to either capture it in a detector or bounce a photon off of it or some such thing. It is that interaction which destroys the two slit pattern. Whether the detection was done by a dog or a robot it does not matter. If you create a signal that localizes the electron to one of the slits then you destroy the two slit pattern.

Aaaand... that's one too many WTBDWK?! clips on this forum in one year for me. Been fun, guys. Keep up the good conversations on the fringe topics.

This...jeebus.

I blame popular media for perpetuating this horrible myth of an explanation.

+1

Even relatively respectable media have been horrible about misstating this effect. Reams of mystical speculations have been published as a result.

What you and everyone else has said.

The false explanation is that "the observer affects the observed".

Upon this foundation people have built up all kinds of New-Agey and mystical theories about the subjectivity of the universe.

Once I read "ghosts" I stopped reading the OP

I was wondering for a moment if you meant our answer, before I deleted that post. You caught it! Thanks anyway.


As to OP: I value your self critizism:

delayed choice quantum erasure

Am I reading this right? Are you saying my explanation is a horrible myth?

No? See my and Micturition Man´s posts above.

Actually, ghosts are a real thing in quantum field theory (I'm not kidding).

Thanks for posting this! Seems to refute what others above said about it being a "horrible myth". No??

If true, this experiment would show that it is not simply the detection or the bouncing of a photon that changes the experiment, but the actual act of observing the information(or the possibility to do so) is what changes it.

Observation in this context just means a photon colliding with the electron

I was aware of this experiment and it is fair to say that my explanation was overly simplistic, but I was just dealing with the question of the OP and trying not to generate a wall of text.

The eraser experiment does not actually deal with the consciousness of the observer except that the result of the experiment is not known until someone looks at the detectors. That is not particularly profound, at least no more than the question "If a tree falls in a forest where there is no one around to hear, does it make a sound".

The interesting thing in the eraser experiment is that it separates the interference pattern from the detection question to some extent as photons are all treated similarly and the detection of the path happens after the generation of the pattern. IMO what this shows us is that our picture of particles and waves and our understanding of the real mechanism of causality are incomplete. It is very interesting stuff but does not connect to the question of consciousness directly.

For what its worth, I am a theist and pretty much believe that consciousness and free will are real. I am also a scientist and I cannot see that this experiment connects with that issue.

Now I am not saying that any of this does have to do with consciousness, but this sentence I do not think really sums up this experiment.

It is clear from the quantum eraser experiment that the detectors is not what causes the pattern to change. You have the same detectors in QE experiment where we cannot possibly know where the particle came from as the ones that we can know where the particle came from. So it appears on the surface at least that the one variable that changes is the "ability to know" where the particle came from.

I am more than happy for you to tell me why I am wrong, but I don't think that you are adequately representing how odd the results of this experiment are.

Correct. Your explanation is the 'horrible myth' to which I was referring. The idea that "consciousness collapses the wavefunction" which is what directly led to your question about this being a test for consciousness.

It's not consciousness: it's measurement.

The Heisenberg Uncertainty Principle is an epistemological problem, not one of physics. The position and momentum of an electron is not actually indeterminate in any physical sense: it's indeterminate in that we can't measure both simultaneously. We can't measure both because our methods of measurement create an interaction which only allows us to measure one at the cost of not measuring the other.

FAR too often this has been taken to mean that it's actually physically indeterminate: not only can we not determine both the position and the velocity of an electron (or whatever), but its exact position/velocity is indeterminate in some physical sense. This is nonsense. Hey, it may be true, but it doesn't follow from anything said that this is what it means. The interaction of measurement is that we fire a particle to measure another particle: it creates an interaction that results in a different outcome than had we not tried to measure it. This isn't "consciousness" creating an interaction.

There are two horrible myths:

That quantum has established that there is real indeterminacy in the universe (it may merely be epistemological).

That consciousness collapses the wavefunction (it's measurement).

I am confused. Are you saying that consciousness does collapse the wave function?

Would you please reread my post and then comment again. I do not see how I said that consciousness is the cause of wavefunction collapse.

The results are very odd from an intuitive point of view. If you agree that it is not a test of consciousness, then we have no dispute.

I'm responding to OP...I don't care to keep people's names straight

How would you go about testing the hypothesis that it is consciousness which collapses the wave?

So...when you make a comment, even when you begin the comment with a quote of someone else, you are always responding to the OP, not the quoted passage? Does that make sense? If you answer this, are you responding to me or the OP? How can we even begin to have a rational discussion under those terms?

I do not know how to craft an experiment that distinguishes between the presence and absence of consciousness.