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"It's not clear to me..."

It's not just you, Michael.
Particle-wave duality and the various expressions of the double slit experiment, the Heisenberg principle, quantum entanglement and its interactions at a distance, mathematics embedded in the cosmos, the illusory nature of time, the hard problem of consciousness...this list could go on and on.

Sometimes, as linear thinking humans, I think we're all missing Something that we may never be able to fully grasp intellectually.

But that shouldn't stop us from trying.
:-)

I didn't "read" the article per se, but from what I've come to know, "measuring" subatomic particles involves hitting them with other subatomic particles (electrons or photons). This is just my speculation, but "steering the nuclear spin by applying sequential measurements" might be like steering a boat by throwing tennis balls at it from shore. There's definitely the intention of the experimentor to steer the nucleus, but I don't think it would necessarily involve PK like altering random sequences. With measuring single particles I'm not sure how one could separate the conscious intention and the physical act of hitting it with another particle to make the actual measurement.

This whole area is so complex and counter-intuitive that your thinking that this has some direct relevance to consciousness (as usually defined) is understandable. A lot of the confusion comes from vocabulary derived from Bohr's extreme naive objectivism, most particularly that misleading term "observation". A much better term (though still not quite right) would be a "measurement".

Once upon a time one could reasonably speculate that "observation" in QM meant "observation by a conscious entity" -- because Bohr's formulation carefully avoided defining just what an observation was -- essentially (and I'm simplifying) his opinion was that it is specious metaphysics to ask the question beyond a strictly operational sense. Although others considered the possibility that consciousness was involved he rejected it outright.

There is room today for putting consciousness into QM but it requires some extreme jumping through hoops and it doesn't directly address "observation" but something rather meta.

We now know that the effects of "observation" in the Copenhagen interpretation occurs without any consciousness directly involved. A quantum system is "observed" whenever it takes part in a non-reversable interaction -- that is, an interaction that is unlikely to be spontaneously undone, the egg cannot be unscrambled and reassembled.

It would be nice if "observations" only happens when a conventionally conscious being is paying attention. Then we would be able to play with really powerful quantum computers. What makes it difficult to build a quantum computer is that they "decohere", like trying to use a conventional computer made of ice in a blast furnace. Decoherence is an affect of "observation." It would be nice if we could avoid it by having everyone involved go off and read a distracting book while it churns out the answer, but alas its the table its sitting on, the air around it, the container its in, that are "observing it".

The relatively recent work that's being done with "weak quantum measurements" has been fascinating, but they don't change the the fundamental nature of what a QM observation is, just show that there is some surprising subtlety derived directly from the traditional mechanisms. One way of looking at it is that it has been found that it is possible to make some quantum systems self-repairing as long as you're willing to probe very gently for a long time and include an "ablation shield".

This experiments seems to be doing just that, but shifting what counts as that shield to steer the whole system -- like a sculptor chiseling a lump of marble. But the scientists aren't making these observations -- they couldn't possibly react fast enough to choose the next observation to make. They set up a mechanism to make the observations and choices for them.

Erudite and excellent comment by Topher!

"This whole area is so complex and counter-intuitive that your thinking that this has some direct relevance to consciousness (as usually defined) is understandable. A lot of the confusion comes from vocabulary derived from Bohr's extreme naive objectivism...."

Topher

How would you explain the "Renninger" type experiment results. This seems to be an observation (collapse) without any physical "measurement." Simply a collapse of the wave function by the mind seeing "nothing," at least according to Prof. Richard Conn Henry. I don't pretend to understand this stuff either, but there seems to be differing opinions amoungst the scientists too.

GregL

Dr Henry, without question, knows QM much more deeply than I ever will. However, it seems to me that he has a strong tendency towards confirmation bias -- specifically to take phenomena consistent with his theories as evidence for his theories, even when they are also consistent (although generally non-obviously) with what are now considered the more conventional view.

'"I only wish I had such eyes," the King remarked in a fretful tone. "To be able to see Nobody! And at that distance, too! Why, it's as much as I can do to see real people, by this light!"'

A failure to interact is still an "observation". Not "seeing" something in a particular place where it might have been reduces our uncertainty about where the object is.

Renninger's original thought experiment showed that an interesting characteristic of "negative" observations for QM is that they can collapse the wave function only partially -- if we learn where something is not, then we still do not know where it is, and in QM, this means that it actually is everywhere else that it could be. His formulation was entirely in terms of mechanical measuring apparatuses, and since we now know that no conscious being has to read the results of the apparatus for collapse to occur, consciousness would not seem to be a direct factor in the phenomena.

I really haven't seen anything to indicate that any of the elaborations -- both as thought experiments and as approximate physical experiments -- that have come up since really change this -- however much they stretch our ability to understand them semi-classically. The sophisticated thermostat that "observes" that no one is home and turns down the temperature is not thereby to be deemed conscious.

Thanks Topher

I had some direct contacts with Dr. Henry and he pretty much stands by his interpretation of the Renninger result affirming that this is a "mental" universe.
You know, if you were to allow for von Nuemann's interpretation here, he is probably right, as the mechanical apparatus is merely another quantum system. Prof Henry also referred me to the quantum Zeno effect as further evidence supporting his view. But, as you say, that is his position.

Thanks for your response.

GregL

And yet, the experimental evidence for the Quantum Zeno Effect (i.e., that a continuously "observed" QM system will never change state -- e.g., a continuously observed radioactive nucleus will never decay) involves apparatus which recorded the same "evidence" for collapse regardless of whether or not someone was observing the apparatus.

Van Neumann's interpretation was that the "cut" from quantum to classical phenomena could be made anywhere between the quantum phenomenon and a conscious observer -- because where that point fell was irrelevant to the experimental outcome. Some of interpreted this as showing that consciousness, as the only distinguished point, must be the deciding factor. Von Neumann's opinion, however, was that this showed that it is meaningless to assign any specific position to the cut, including at consciousness.

In any case, Von Neumann's assumption has been shown to be wrong. One can design an experiment in which you can demonstrate the cut occurs before consciousness and this has been found to be the case.

As I said, there is room to have consciousness driving things, but only at a meta level. Previously the hypothesis that consciousness "causes" (its not clear that that would represent causality in the classic sense) the collapse of the wave function. It's now known, though, that consciousness (at least in the sense of something specifically associated or at least strongly concentrated in the human mind), is not at all necessary for this to occur.

We are left with the hypothesis that it is not the wave function collapse that consciousness triggers but that there is a meta system in which the collapse itself occurs (apparently as a result of irreversible interactions) but that occurrence results in a meta-superposition of collapsed states, which in turn only collapses when consciousness interacts with it. The problem with this is that, unlike collapse of the wave function, there is no observable phenomenon that gives us reason to suppose that this occurs. There is no difference between this and a classical physicist asserting that the universe only comes to exist when someone is aware of it.

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