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title: QM and consciousness (for people who don't like math)

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# QM and consciousness (for people who don't like math)

When people say that QM has nothing to do with consciousness, they usually mean _consciousness in general_ --- and this is (probably) true. On the other hand, _your_ consciousness is indeed relevant: it is the point at which quantum events attain definite outcomes for you.

You may find this fascinating or boring, but most popular treatments --- both technical and "New Age" --- tend to misrepresent it. I'd like to remedy that.

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A single particle can be in a **superposition**. It is possible to _prove_ that it's in superposition by something called an **interference experiment.** As the superposition interacts with other particles, they _join_ the superposition (i.e., become **entangled** with it). As far as we know, this is true even if those "other particles" constitute a conscious being. In this way, the superposition just keeps growing and growing forever[^collapse].

[^collapse]: Interpretations of QM can be broadly divided into _collapse_ and _no-collapse_. The former state that superpositions undergo a real physical collapse. Technically, their distinct predictions make them distinct _theories_, and not _interpretations_ of QM. The vast majority of physicists are in the no-collapse camp. This piece takes the no-collapse perspective, and is agnostic about interpretation.

However, doing an interference experiment requires careful control of _all_ particles in the superposition. If you leave out even _one_ particle, the remainder will behave classically. In other words, they will _appear_ to have collapsed. This has a few immediate consequences:

1. In the double-slit experiment, once the electron entangles with the detector at the slits, the electron _by itself_ will no longer show interference. There is nothing spooky going on here, and it has nothing to do with consciousness. This is something that popular explanations of QM often get wrong:

> *The electron **decided** to act differently, as though it was **aware** that it was being watched!*
>
> -- New Age movie [What The Bleep](https://youtu.be/5WV1SMoVYDM?t=266)

In fact, when the electron entangles with the detector, they are still in a (joint) superposition of _left_ and _right_ outcomes, which then grows to include the screen, etc.

2. If you want to _prove_ that a system is in superposition, you must keep it perfectly isolated from air molecules, photons, etc. Otherwise, you will be unable to wrangle all the particles necessary to perform your interference experiment. The system will then _appear_ to be classical. In practice, such isolation is almost impossible.
 
This apparent loss of superposition is called **decoherence**. But crucially, it is only _apparent_ --- a fact that most popular explanations misconstrue (emphasis mine)[^decoherence]:

> *If you simply stick a cat in a box and link its fate to the outcome of some quantum event, you’re not likely to put it in a superposition of alive and dead, because decoherence will almost instantly **force** it into one state or the other.* --- A physics Ph.D. writing for [Quanta Magazine](https://www.quantamagazine.org/real-life-schrodingers-cats-probe-the-boundary-of-the-quantum-world-20180625/)

[^decoherence]: 

    The [Stanford Encyclopedia of Philosophy](https://plato.stanford.edu/entries/qm-decoherence/#SolMeaPro):

    > Unfortunately, naive claims of the kind that decoherence gives a complete answer to the measurement problem are still somewhat part of the ‘folklore’ of decoherence, and deservedly attract the wrath of physicists (e.g. Pearle 1997) and philosophers (e.g. Bub 1997, Chap. 8) alike.

    [Physics StackExchange](https://physics.stackexchange.com/questions/373905/):

    > But the collapse itself is not explained [by decoherence], there is still the sum [*N.B.: superposition*] in the above formula, still an "and" ...

It is not "forced" into anything. The cat + environment is theoretically still in a massive superposition; just one that is effectively impossible to do anything interesting with.

Eventually, _you_ become entangled with it. At this point, it is not even _theoretically_ possible to do an interference experiment, because you would have to stand outside yourself to include "both versions of" you. Therefore, at this point you can finally say that there is a single definite result (even if you don't know what it is).

On one hand, this shouldn't be surprising: we're just saying that there is a result _for you_ when the system entangles with _you_. That's a tautology, given the rules as we know them: from the perspective of _any_ of the particles in the chain, the "collapse" happens precisely when _it_ becomes entangled. In this sense, you are not special. 

On the other hand, _you_ cannot take any perspective but your own --- and from _that_ perspective, you are indeed "special," in a physically meaningful way. You are the point at which quantum events suddenly obtain definite results in "your world" --- aka the place you normally call "the world." This fact is effectively impossible to exploit or even prove (thanks to decoherence), but it is a straightforward reading of the theory.

Moreover, what does "you" mean here? After all, you can treat your big toe as just another external physical device. As you work your way back, you will find yourself closing in on _your consciousness_[^consciousness].

Although this perspective has become unpopular in recent years, I am certainly not alone in finding it fascinating:

> *I think consciousness will remain a mystery. Yes, that's what I tend to believe. I tend to think that the workings of the conscious brain will be elucidated to a large extent. Biologists and perhaps physicists will understand much better how the brain works. But why something that we call consciousness goes with those workings, I think that will remain mysterious. I have a much easier time imagining how we understand the Big Bang than I have imagining how we can understand consciousness.*
> ...
> *I’m not going to attempt to define consciousness, in a way that’s connected with the fact that I don’t believe it will become part of physics. And that has to do, I think, with the mysteries that bother a lot of people about quantum mechanics and its applications to the universe.*
> ...
>  *Quantum mechanics kind of has an all-embracing property, that to completely make sense it has to be applied to everything in sight, including ultimately, the observer. But trying to apply quantum mechanics to ourselves makes us extremely uncomfortable. Especially because of our consciousness, which seems to clash with that idea. So we’re left with a disquiet concerning quantum mechanics, and its applications to the universe. And I do not believe that disquiet will go away. If anything, I suspect that it will acquire new dimensions.*
>
> -- Edward Witten, a physicist so overpoweringly brilliant that his fellow string theorists casually throw around terms like ["smarter than anyone else"](http://www.nytimes.com/1987/10/18/magazine/a-theory-of-everything.html?pagewanted=all) and "head and shoulders above the rest."

[^consciousness]: To be clear, "consciousness" cannot refer to our usual, commonsense definition. For example, suppose different colored lights turn on depending on whether the Cat lives or dies. Furthermore, suppose you don't know which light is which --- in fact, you don't even realize that the lights signify anything at all. Maybe you only catch a glimpse from the corner of your eye. By any reasonable account, you are _profoundly_ entangled with the system, even though you are not "conscious" of it in the usual sense.

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## The "Law of Attraction?"

Another area that's become popular in New Age movements is connecting QM to the "Law of Attraction." But what (if anything) does the science have to say?

So far we have said that quantum events attain definite results when they reach _you._ But as far as we know, _which_ result is obtained is completely random. Nothing would permit you (or anything else) to _decide_ or _influence_ the result.

On the other hand, the very _meaning_ of "random" is hotly debated. All we know is that (1) nothing allows us to _predict_ the outcome (a finding that won people the Nobel Prize in 2022), and (2) any _sequence_ of outcomes (for the same experiment) seems to be statistically random.

Questions like "_why_ did I end up in this branch?" are denied meaning. A perfectly valid answer is "actually, (a copy of) you ended up in both!" You might press further: "okay, but why did _this me_ end up in _this branch_?" and the answer would be "well, that's what it _means_ to be 'this you'!"

Such difficulties plague _all_ (no-collapse) interpretations, and not just Many Worlds.

Therefore, if you claim to be _choosing_ which branches you follow, well, there's nothing that physics could really say about this. Nothing could specifically _prevent_ it, because the claim doesn't even have physical _meaning_. By the same token, physics cannot _support_ your claim, either.

In the end, any such "ability" would only appear as a statistical anomaly, with no possibility of _explanation_ in the usual sense. 

## Quantum biology

Another area that we ought to touch on is _quantum biology._ There are many fascinating findings in this field, but the one I find most exciting is this: human beings are able to detect _single photons_ (above chance) at the conscious level.

Why is this interesting?

Consider the Schrodinger's Cat apparatus. It starts with a single molecule, and the quantum uncertainty gets magnified up to the macroscopic level. Such "amplification" is ridiculously contrived, and was not believed to happen commonly in nature: most quantum events leave no visible traces in the world. Now we are finding that _human brains_ can act as such amplifiers.

Therefore, between the time you go to sleep and when you wake up, billions of people might be making macroscopically-relevant decisions. This means that the space of possible worlds you could wake up to might be tremendous, indeed.

If you turn out to have any magical abilities, now might be the time to use them ;)