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On Sep 20, 2010, at 12:19 AM, nick herbert wrote:

Yu Shan & Danko--

After thinking over your argument I am beginning to believe that it has some merit.

One of the oddest facts about experiments of this kind is that the mere possibility of gaining "which-path" information will prevent interference from occurring. You do not have to actually carry out the "which-path" observation. Henry Stapp summarizes the gist of quantum mechanics thus: "things that could have occurred but didn't, influence the things that do occur."

It is almost as tho you don't have to act to change a quantum system--the MERE THREAT OF ACTING can do so.

The second fact about this threat is that it makes no difference how it would be carried out--using machines or conscious awareness-- any way of recording that knowledge is as good as any other for carrying out this threat. Which of course need never be carried out.
It seems to me that there is some way of formulating this insight better--to say that in this particular situation, the mere possibility of recording "which path information" REGARDLESS OF HOW THAT RECORDING IS PERFORMED can be construed to mean that quantum mechanics itself gives consciousness no special role.

I am sure that there is some better way of formulating this. It is the same argument you are making but from a slightly different perspective because it does not deal with real measurements but only with the possibility of making measurements.

Surprise. I think I'm back on your side.
I will keep playing with these concepts till they get clearer.

Thanks again for a most stimulating exchange.

Nick Herbert


On Sep 19, 2010, at 9:01 AM, Yu Shan wrote:

Nonetheless I think it is good to do experiments for which 'the
outcome can already be inferred on the basis of existing theoretical
frameworks' because when the outcome is different that really tells us

I agree. It's the reason that we cite the actual experiments to show
that there is no interference, rather than giving theoretical argument
only.


On Sep 20, 2010, at 2:13 AM, Hrvoje Nikolic wrote:

Hi Nick, Yu, and Danko!

I agreed with the first objection by Nick in his first e-mail, but I would like to make some comments on these last comments by Nick.


"One of the oddest facts about experiments of this kind is that the mere possibility of gaining "which-path" information will prevent interference from occurring. You do not have to actually carry out the "which-path" observation."

But in order to ACHIEVE the possibility of gaining "which-path" information, you MUST do something PHYSICAL. Namely, you need to put or remove some piece of experimental equipment. It is THIS PHYSICAL change that makes the physical system different.


Henry Stapp summarizes the gist of quantum mechanics thus: "things that could have occurred but didn't, influence the things that do occur."

But something HAS occurred here. You have put or removed a piece of experimental equipment.

"It is almost as tho you don't have to act to change a quantum system--the MERE THREAT OF ACTING can do so."

It depends on what do you mean by "quantum system". If the pieces of experimental equipment count as parts of the quantum system, then you DO NEED to change the quantum system.

"The second fact about this threat is that it makes no difference how it would be carried out--using machines or conscious awareness-- any way of recording that knowledge is as good as any other for carrying out this threat. Which of course need never be carried out.
It seems to me that there is some way of formulating this insight better--to say that in this particular situation, the mere possibility of recording "which path information" REGARDLESS OF HOW THAT RECORDING IS PERFORMED can be construed to mean that quantum mechanics itself gives consciousness no special role."

It is well known that machines can influence the wave function.
(That's why the pieces of experimental equipment do what they do,
as I repeated above.) In principle, the brain can influence the wave function too. (In fact, in
http://xxx.lanl.gov/abs/1006.0338
I have argued that this implies that nonlocal entanglement can, in principle, be used for a sort of superluminal communication.)
However, I have no idea how conscious awareness itself, except as a PHYSICAL CONFIGURATION OF THE BRAIN, could influence the wave function.
...

Best regards,
Hrvoje Nikolic