Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

Can someone explain the quantum physics-consciousness connection? In the double slit or quantum eraser experiments, the system behaves as a whole, with some apparent time independent traits. Invoking some kind of time independent but still causal physics, the problem could be simplified. But to include consciousness in the picture, we need better evidence. So I'm going to propose the following version of the double slit experiment.

If consciousness was actually involved, a person could create or destroy the interference pattern by just looking at the slit measurement result even after it is recorded. To emphasize my point, imagine that the experiment is spread across 3 days. The first day experiment is done but the results are recorded into computer memory and no one looks at it. The second day someone comes in and just looks at the results of the slit detector. He/she could even encode some message by closing and opening his/her eyes while looking at the results. Since consciousness is involved, it should effect the interference pattern even after such an indirect and delayed measurement (by consciousness). Then on the third day a second person could just look at the interference pattern that was recorded two days earlier, and still see the interference pattern being created and destroyed and even read the encoded message by just looking at the slit measurements on the second day. Does this sound reasonable to you, or what am I missing?

share|improve this question
1  
As far as I can tell, there is no logical definition of consciousness that compatible with physics. –  Antillar Maximus Jan 5 '13 at 15:52
    
Hi @Anixx: A philosophy tag is not allowed, cf. this meta Phys.SE post. –  Qmechanic Jan 5 '13 at 22:51
    
This question sounds like a misunderstanding of the theory. As far as I've been able to ascertain, the idea isn't that your conscious observation interferes, it's that on such a small scale, any observation physically effects a change in the system. When you are monitoring electrons, you have to "observe" them by bouncing photons off them with a sensor; this obviously interferes with their behavior. Watching it with your eye won't affect it, unless you're Superman. –  ArmedMonkey Jul 19 '13 at 14:06
add comment

5 Answers

Can someone explain the quantum physics-consciousness connection?

There is none.

There's a whole lot that can be said about this, but at a basic level, the explanation is that an observation in quantum mechanics is best thought of as an interaction with another particle (technically: a classical system). It doesn't have to involve a conscious observer. So in your example, storing the result into computer memory is equivalent to looking at it, and there will be no further effect on the recorded interference pattern.

If you could treat the computer memory as an incoherent quantum system (i.e. non-classical, so that storing into memory wouldn't collapse the wavefunction), and if I understand correctly what you're saying, the example you've proposed sounds pretty much like the delayed choice quantum eraser experiment. This experiment works like the double slit experiment with the difference that you can choose whether or not to detect which slit the photon went through after it has passed through the slits. The results are consistent with quantum mechanics in the sense that you still get the interference pattern if you don't identify the slit, and you don't get the interference pattern if you do identify the slit, despite the choice being made afterwards.

share|improve this answer
add comment

No, quantum physics doesn't need consciousness, Hydrogen atoms were radiating their discrete line spectra long before consciousness evolved. The products of those emission events are only just reaching us now.

share|improve this answer
    
Thanks all. So you're saying the consciousness connection is an oversold aspect of the theory. Perhaps shows the incompleteness or a lack of understanding of what's lies beyond our common sense. But I still don't see why well known scientists are making a big deal of it. By doing this, they just let the thing be hihacked by the religious. –  user17498 Jan 5 '13 at 18:25
    
@user17498 Consciousness is not an oversold aspect of quantum theory, is not an aspect of it at all. I think 99 % of all sane physicist consider "quantum consciousness" as part of the crackpot domain I'm afraid. The logic is explained well in the introduction of this article: rationalwiki.org/wiki/Quantum_consciousness –  Heidar Jan 5 '13 at 19:51
add comment

In addition to David's answer I observe the following:

Too much emphasis is placed on the simple double slit experiment as far as the possibility of defining a wavefunction and the probabilities arising thereof. IMO the destruction of the interference pattern is due to the Heisenberg uncertainty relation, taking into account the slit separation and the measurement errors.

In a modified experiment with two slits

In a quantum mechanical two-slit experiment one can observe a single photon simultaneously as particle (measuring the path) and as wave (measuring the interference pattern) if the path and the interference pattern are measured in the sense of unsharp observables. These theoretical predictions are confirmed experimentally by a photon split-beam experiment using a modified Mach—Zehnder interferometer.

A similar experiment with electrons:

electron double slit modified

Electron buildup over time

These show in my opinion that the wave function, even if it is a complicated one, is truly a probability distribution for the statistical appearance of a particle, nothing esoteric about it.

share|improve this answer
3  
Well, maybe a "little" esoteric, in that amplitudes for different alternatives interfere :-) –  twistor59 Jan 5 '13 at 8:45
add comment

As stated by @AnnaV @DavidZaslavsky and @Twistor59 there is none. In fact, you can formulate quantum mechanics without needing any observer. And this is good because, for instance, the interference pattern will be recorded by instruments even when there is no physicist at the lab. I recommend a modern textbook on quantum mechanics such as R. B. Griffiths' Consistent Quantum Theory. Some relevant excerpts:

Measurements play no fundamental role in quantum mechanics, just as they play no fundamental role in classical mechanics. In both cases, measurement apparatus and the process of measurement are described using the same basic mechanical principles which apply to all other physical objects and physical processes. Quantum measurements, when interpreted using a suitable framework, can be understood as revealing properties of a measured system before the measurement took place, in a manner which was taken for granted in classical physics. See the discussion in Chs. 17 and 18. (It may be worth adding that there is no special role for human consciousness in the quantum measurement process, again in agreement with classical physics.)

[...]

Both quantum mechanics and classical mechanics are consistent with the notion of an independent reality, a real world whose properties and fundamental laws do not depend upon what human beings happen to believe, desire, or think. While this real world contains human beings, among other things, it existed long before the human race appeared on the surface of the earth, and our presence is not essential for it to continue.

The idea of an independent reality had been challenged by philosophers long before the advent of quantum mechanics. However, the difficulty of interpreting quantum theory has sometimes been interpreted as providing additional reasons for doubting that such a reality exists. In particular, the idea that measurements collapse wave functions can suggest the notion that they thereby bring reality into existence, and if a conscious observer is needed to collapse the wave function (MQS state) of a measuring apparatus, this could mean that consciousness somehow plays a fundamental role in reality. However, once measurements are understood as no more than particular examples of physical processes, and wave function collapse as nothing more than a computational tool, there is no reason to suppose that quantum theory is incompatible with an independent reality, and one is back to the situation which preceded the quantum era.

share|improve this answer
add comment

It does not matter whether the observer looks at the observed system or not. This is because even if he does not look at it, technically he already observed the result because he is connected to the measurement apparatus via external medium (such as air of the atmosphere).

Only of the observer thoroughly isolated from the external medium, he can affect the experiment by looking at the result.

share|improve this answer
add comment

protected by Qmechanic Jun 10 '13 at 22:08

Thank you for your interest in this question. Because it has attracted low-quality answers, posting an answer now requires 10 reputation on this site.

Would you like to answer one of these unanswered questions instead?

Not the answer you're looking for? Browse other questions tagged or ask your own question.