Quantum Mechanics, Nothing to do with Consciousness

Epistemic sta­tus: A quick re­jec­tion of the quan­tum con­scious­ness woo. If you have already read the se­quences, there’s noth­ing new in here. If your new to the site, or need a sin­gle page to point peo­ple to, here it is.


Real Quan­tum me­chan­ics looks like pages of ab­stract maths, af­ter which you have de­duced the re­sults of a physics ex­per­i­ment. Given how hard the maths is, most of the sys­tems that we use quan­tum me­chan­ics to pre­dict are quite sim­ple. One com­mon ex­per­i­ment is to take a glass tube full of a par­tic­u­lar el­e­ment and run lots of elec­tric­ity through it. The el­e­ment will pro­duce coloured light, like sodium pro­duc­ing or­ange, or neon pro­duc­ing red. So take a prism and split that light to see what colours are be­ing pro­duced. Quan­tum ph­ysi­sists will do lots of tricky maths about how the elec­trons move be­tween en­ergy lev­els to work out what colour differ­ent el­e­ments will pro­duce.

There have been no quan­tum me­chan­ics ex­per­i­ments that show con­scious­ness to have any rele­vance to par­ti­cle physics. The laws of physics do not say what is or is not con­scious, in much the same way that they don’t say what is or is not a work of art. Of course, con­scious­ness is a prop­erty of hu­man brains, and hu­man brains, like ev­ery­thing else in the uni­verse, are made of elec­trons and quarks play­ing by quan­tum laws. The point is that hu­man brains are not sin­gled out for spe­cial treat­ment, they get the same rules as ev­ery­thing else.

For the writ­ers among you, think of a word pro­ces­sor fea­ture that takes some text, and turns it into ALL CAPS. You can put a great novel into this fea­ture if you want. The point is that the rule its self acts the same way whether or not it’s given great liter­a­ture. You can’t use the rule to tell what is great liter­a­ture, you have to read it and de­cide your­self. Con­scious­ness, like liter­a­ture, is a high level view that’s hard to pin down pre­cisely, and is largely a mat­ter of how we choose to define it. Quan­tum me­chan­ics is a sim­ple, mechanis­tic rule.

Yes I know that some of you are think­ing of the dou­ble slit ex­per­i­ment. You make a screen with two slits, shine light through and get an in­terfer­ence pat­tern. Put a de­tec­tor at one slit, at­tach a dial to the de­tec­tor, and have a sci­en­tist watch­ing the dial so they can see which slit the pho­ton went through, and the in­terfer­ence pat­tern dis­ap­pears. Per­haps, thought some of the early sci­en­tists, con­scious­ness causes the quan­tum wave func­tion to col­lapse, the uni­verse doesn’t like us know­ing which slit the pho­ton goes through.

How­ever, lets do a few more ex­per­i­ments. Re­peat the pre­vi­ous one, ex­cept that the sci­en­tist is sleep­ing in front of the dial. No in­terfer­ence pat­tern. Turn the dial to face the wall, re­move the sci­en­tist en­tirely. Still no in­terfer­ence pat­tern. Un­plug the dial from the de­tec­tor, so elec­tri­cal im­pulses run up the wire and then can’t go any­where. Again, no in­terfer­ence. What­ever is stop­ping in­terfer­ence pat­terns, it looks like de­tec­tors, not con­scious­ness.

It turns out that any in­ter­ac­tion with any other par­ti­cles, such that the po­si­tion the other par­ti­cle ends up in de­pends on which slit a pho­ton went through, cre­ates en­tan­gle­ment be­tween the pho­ton and the other par­ti­cle, which de­stroys in­terfer­ence. And the atoms in the dial, the elec­trons in the wire, and par­ti­cles in the de­tec­tor its self, all have there po­si­tion de­pend on where the pho­ton went.

In gen­eral, the way to get rid of mys­ter­ies is to break them up into smaller mys­ter­ies, un­til your left with loads of tiny mys­ter­ies. How life worked used to be one big mys­tery. But thanks to mod­ern biol­ogy, we now have thou­sands of tiny mys­ter­ies about how yeast metabolism can tol­er­ate high lev­els of al­co­hol, or how pro­to­zoa DNA doesn’t get tan­gled when they repli­cate. And these are sur­rounded by large amounts of well un­der­stood sci­ence. (I’m not a biol­o­gist, so these par­tic­u­lar things might be solved by now, but you get the Idea) Big mys­ter­ies get bro­ken down into a pile of fact, and sev­eral smaller ones.

Glu­ing the “mys­tery” of quan­tum me­chan­ics, to the “mys­tery” of con­scious­ness to make a big­ger and more mys­te­ri­ous mys­tery, would be a mis­take even if both of these things were ac­tu­ally mys­ter­ies to hu­man­ity. Mys­tery is a blank text­book, not a fea­ture of the world, and in this case, there is a clear pic­ture of quan­tum me­chan­ics, and a rough sketch of con­scious­ness in the text­books.