Sunday, January 9, 2011

Quantum Psychology

This link seems pretty high on the "woo woo stuff claiming to be science" scale--but that's the predjudice we physicists have toward psychologists anyway.

(That was a joke, you can stop throwing tomatoes now.)

Actually, I say why not, if other psychologists find it up to snuff, I see no reason why it's not an interesting and plausible study that is worth more research.  To wit:

"One of the most respected, senior and widely published professors of psychology, Daryl Bem of Cornell, has just published an article that suggests that people — ordinary people — can be altered by experiences they haven't had yet. Time, he suggests, is leaking. The Future has slipped, unannounced, into the Present. And he thinks he can prove it."

Without claiming that this explains it, I will say that the framework of quantum mechanics would permit something like this to be within the realm of the possible, and our understanding of quantum mechanics is getting so good that I would not be terribly surprised if we did begin to see quantum effects appearing in realms of science even very removed from pure physics.  That being said, actually linking the effects credibly would be beyond the scope of either branch of science individually and pretty damn difficult all around.

When I was an undergrad I performed a lab experiment called the "quantum eraser," in which I took the extraordinarily simple case of a beam of light emitted by a laser (thus, all the little light particles were suitably similar to each other as is unique to how lasers, masers, and the like emit light), and made the photons act a certain way based on what I did after the experiment was over.  

It was called the "quantum eraser" because of what the laser light looked like on the wall, after I shone the laser beam through a screen with two slits.  Usually, the light pattern looks something like this, which is notably different from the single dot of light your cat likes to chase across the floor. This laser dot looks like a prison window grill instead because when it passed through two slits, it interfered with itself.  Bring up the usual analogy to dropping two rocks in a pond and watching how the ripple patterns change when they intersect each other:  some places get extra big ripples, in some places the ripple goes away, and that's the beauty of things that are waves.  Light is a wave, and it's also a particle--welcome to your very first step on the journey down the rabbit hole of quantum mechanics.

When I added in polarizers after each slit, so that light passing through one of the two slits could be distinguished from the light passing through the other one, I stopped seeing the prison-grill pattern and started seeing a normal dot of light again--I erased the pattern.  But why should simply distinguishing the light from each beam do that?  There is no reason that it should, except that quantum mechanics illogically says that in a situation such as each little light photon was supposed to have faced, whereby it arrives at Door #1 and Door #2 and has to pick one, but I, the observer, have no way of telling which one it actually picked, then it doesn't pick.  It just behaves as if it went through both.  Since it behaves that way, it can interfere with itself and make a light pattern that shows interference.

When I changed the experiment so that I could tell which slit the photons went through, then I observed what would happen if half had gone through one and half had gone through the other:  just a dot, no interference.  Furthermore the polarizers were located behind the slits:  the light had already passed through by the time it reached them, yet being there, giving me the ability to tell what had happened, was enough.  Even weirder, when I added in another polarizer downstream that erased the information the first polarizers had gathered--I'd see the stripes again, instead of the dot.   All done after the light had gone and passed through the slits.

This is called delayed choice.  One interpretation is that I can choose the outcome of the experiment based on what I want to observe, and it doesn't matter that I make that choice after the event I am observing actually happens.  It doesn't necessarily make sense with how we usually interact with the world but it does make sense with the statistically-driven rules of quantum mechanics, and certain situation can be manipulated to reveal that weirdness.*

Of course, delayed choice doesn't have to be interpreted to mean that the future affects something that happened in the past.  It could for instance mean that something you do in the present is only clarifying the past, or, as some of the people who first came up with the idea for delayed choice said, "the past has no existence except as is recorded in the present,"--which removes the time-travel-esque aspect.  You could interpret it just as an example of probability threading it's way into real life--which is indeed how many people choose to interpret all of quantum's weirdness.  Sometimes a roomful of physicists will not all agree on how to interpret how the heck subtle quantum mechanics things actually happens in reality, and physics is a field that is running into a wall on that whole "absolute objective reality" idea anyway--despite the fact that the math and general theories behind quantum mechanics are basically a settled science and research into how to use QM to make a better computer and help your GPS find itself, not to mention transmit information in space-age ways, are well underway.

So if a psychologist finds statistical significance to the idea that something we do in the present seems to inform something we've already done in the past--or however you want to interpret it--and if he has a carefully controlled and eventually repeated experiment, then hey, I'll call that an interesting stop in the scientific process.

*I have to put a disclaimer here that since photons are the only known and theoretically allowed things to move at the speed of light, interpreting as an actual example of delayed choice the experiment I did with just photons runs into some problems with special relativity. Ah well, the big problem in physics these days is that relativity and quantum mechanics don't mix.  The entire setup, minus the lab components, is equally valid for electrons except that it costs a great deal more than the lab practical budget for an undergraduate physics department, in which case you have to admit you're in spooky-land because electrons, as clear particles, are then nonetheless doing some suspect wave-like things.  And then it turns out that they've even passed fullerine molecules through double slits.

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