I read the Wikipedia article about the Observer effect and I was a bit confused by the wording of the introductory section.

Does the method of observation collapse the wave function (or define the eigenstate, or "define" the quantum state (I don't know the proper terminology here, sorry)) regardless of whether or not consciousness is involved in the observation?

My understanding from the Wikipedia article's introduction was that the uncertainty of the quantum state is interfered with by both conscious and unconscious observation.

Is this true?

  • $\begingroup$ If people feel the Wikipedia article is written in an ambiguous way, can someone please correct it? I feel they tried to make it unambiguous, but inadvertently used ambiguous wording. $\endgroup$ – Thom Blair III May 8 '16 at 14:56
  • $\begingroup$ This quote in particular I find confusing: "As Richard Feynman put it: "Nature does not know what you are looking at, and she behaves the way she is going to behave whether you bother to take down the data or not." Well, what does he mean? Does she collapse the wave function or not whether you take down data or not? $\endgroup$ – Thom Blair III May 8 '16 at 15:00
  • $\begingroup$ I fail to see the ambiguity that you refer to. $\endgroup$ – Keep these mind May 8 '16 at 15:25
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    $\begingroup$ There is no such thing as "the observer effect". There is a deep misunderstanding among many, including physicists, about the fundamental differences in the behavior of open vs. closed systems. In practice all systems are open because electromagnetism (and potentially gravity) are mediated by massless bosons that constantly mix the state of the system with that of the environment. If that mixing is slow, then we can have a short term illusion of a closed system. If it is not, then we need to look at the behavior of the system+environment, which is what you call "the observer effect". $\endgroup$ – CuriousOne May 8 '16 at 22:41
  • $\begingroup$ My suggestion is: let go of EVERYTHING you have ever heard about observers and consciousness in physics and start over from the facts. Learn what the coupling to the environment does to a system. That is real physics and it explains everything that seems strange to you at the moment. $\endgroup$ – CuriousOne May 8 '16 at 22:42

Wave Function collapse is a reconciliation between what quantum mechanics states should occur, and what we classically observe occurring. It is a process in which the quantum superposition of states becomes less important, and a single observed state becomes more important.

Nothing in the equations of quantum mechanics demand the observer effect. You can get something arbitrarily close to the observer effect by choosing to cause interactions which cause the superposition of states to be arbitrarily well modeled by a single state. Doing that does not require the observer effect.

However, what if we want to declare a particle is in a certain state? That phrasing is an anathema to quantum mechanics, except in perhaps the most absurdly constrained problems possible. Yet, in the classical world, we observe particles that are in a certain state all the time. We even measure them that way. This is the realm of the interpretations of quantum mechanics, which try to wed the quantum with the classical experience we live in every day. There are many interpretations, but in the Copenhagen interpretation, wave function collapse is the tool which does the heavy lifting.

The "observer" is a hypothetical classical entity which "causes" waveform collapse such that the quantum mechanics equations turn into the classics equations. It is an outside entity perfectly decoupled from the system which comes in in either a known state, or at least a state which is fully described via probabilities, but whose state is explicitly independent of the state of any and every particle in the system under test.

In reality, no such entity is presumed to exist as an assumption of the equations describing quantum mechanics. Because of all of the interactions on the quantum level which have occurred between particles over billions of years, there is no reason to believe we can pick any arbitrary block of particles and call it an "observer" with absolute certainty. Practically speaking, however, there have been so many such interactions that it is reasonable to believe that, if you isolate what I will call a "proto-observer" from a system long enough, thermal activity will cause enough "unpredictable" interactions that we are willing to make the claim that it is "isolated," and thus an observer. In doing so we make the assumption that any entanglement between the proto-observer and system becomes minuscule enough to be ignored. It's an assumption that is not technically true, but for all intents and purposes, is so true that we rely on it! You can prove this to yourself every day, simply by going through the day and observing that quantum mechanical effects are, for the most part, not visibly affecting your world. Most of us survive each day without calculating any path integral or using any bra-s or ket-s to cross the street.

If you assume classical physics is "real," then you must assume there is a classical "observer" which can "collapse the waveform." In many systems, we can say our detection equipment is an "observer." We intentionally construct such equipment to be well modeled as an observer. However, this is where the real rabbit hole starts. The uncertainty of quantum mechanics shakes the fundamentals of science's empirical approach to the universe. Science is incredibly dependent on the concept of measurement to make its predictions and gauge the quality of its theories. However, measurement is never fully defined within science. If you trace it backwards into the deep still waters of philosophy, it will always trace to one of two things:

  • Some hypothetical entity which does the measurement, but we cannot prove it actually exists.
  • Our own sensory input, from our eyes and ears and touch and taste and so forth. Western philosophy generally assumes "we" exist, along the lines of Descarte's "I think therefore I am," so we can state that this entity exists by assumption.

This is not just a rabbit hole, it is a rabbit hole full of alligators and land mines. If we try to work around this by saying "my equipment does the measurement, and I know it exists," you get into nuanced issues like "how do you know that your equipment actually did a "measurement" at all. Perhaps there is a Descartian Evil Demon deceiving you about the world around you, including your equipment.

That philosophic line of reasoning goes back thousands of years, so its understandable that there is no final answer. However, that line of reasoning is why the "consciousness" and "the observer effect" get entwined. Consciousness is one of philosophy's favorite last-bastion concepts, and the observer effect runs all the way up to it.

Escaping the rabbit hole with our wits intact, most non-philosophers never really have to tug at the concepts of truth, consciousness, or observation quite that hard. (In fact, I might argue that some philosophers might do well not tugging quite so hard, themselves!) If you run the mathematics, we find the "observer effect" is far easier to generate than the philosophers make it seem. It does not take long for a particle at room temperature to interact so unpredictably that it's not worth us considering any subtle entanglements that may still exist. They fall far far far far below the noise floor of our measurements unless we intentionally develop an experiment whose job is to highlight those effects (such as the Delayed Choice Quantum Eraser experiments which are, in my opinion, designed to punish you for trying to apply the observer effect too soon).

For most of our intents and purposes, a small rock is good enough to be an observer. It's only once you really start exploring the nether regions of the concept before we start to see consciousness start to play a part.

... that or small rocks are far more conscious than we give them credit for.

  • $\begingroup$ Thank you very much for your answer. So, to summarize, your answer is "Yes", am I correct? Do you agree with HectorPo's answer below? $\endgroup$ – Thom Blair III May 8 '16 at 15:50
  • $\begingroup$ I cannot see Hector's answer. Is it deleted? $\endgroup$ – Cort Ammon May 8 '16 at 18:15
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    $\begingroup$ @CuriousOne Is that true for all boundary conditions, or just boundary conditions where energy approaches 0 as distance approaches infinity and no reflection occurs? It strikes me that some pathological boundary conditions might lead to different results, such as one which reflect all em energy back into the system. $\endgroup$ – Cort Ammon May 9 '16 at 4:01
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    $\begingroup$ @CortAmmon: If we could make perfect mirrored spheres, then there would be no coupling to the environment and charged quantum systems would be perfectly isolated. We can't, which means that there is always some interaction with the environment. Nature has done something really beautiful for us, though: the self-interaction of the photon is extremely small, i.e. it is "shielded" from itself by the smallness of the coupling. In practice this means that we can look all the way to the beginning of the universe itself. If the photon self-interaction term would be large, all we would see is a fog. $\endgroup$ – CuriousOne May 9 '16 at 7:50
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    $\begingroup$ @CortAmmon: In some ways it's a really strange universe we live in... sometimes we can see so far and then, again, sometimes we can't see almost anything, at all. When I was young I used to get upset about the limitations nature has put on us. As I am getting older, I am beginning to understand the incredible views she has given in return. :-) $\endgroup$ – CuriousOne May 9 '16 at 17:37

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