[SEQ RERUN] On Being Decoherent

To­day’s post, On Be­ing De­co­her­ent was origi­nally pub­lished on 27 April 2008. A sum­mary (taken from the LW wiki):

When a sen­sor mea­sures a par­ti­cle whose am­pli­tude dis­tri­bu­tion stretches over space—per­haps see­ing if the par­ti­cle is to the left or right of some di­vid­ing line—then the stan­dard laws of quan­tum me­chan­ics call for the sen­sor+par­ti­cle sys­tem to evolve into a state of (par­ti­cle left, sen­sor mea­sures LEFT) + (par­ti­cle right, sen­sor mea­sures RIGHT). But when we hu­mans look at the sen­sor, it only seems to say “LEFT” or “RIGHT”, never a mix­ture like “LIGFT”. This, of course, is be­cause we our­selves are made of par­ti­cles, and sub­ject to the stan­dard quan­tum laws that im­ply de­co­her­ence. Un­der stan­dard quan­tum laws, the fi­nal state is (par­ti­cle left, sen­sor mea­sures LEFT, hu­man sees “LEFT”) + (par­ti­cle right, sen­sor mea­sures RIGHT, hu­man sees “RIGHT”).


Dis­cuss the post here (rather than in the com­ments to the origi­nal post).

This post is part of the Rerun­ning the Se­quences se­ries, where we’ll be go­ing through Eliezer Yud­kowsky’s old posts in or­der so that peo­ple who are in­ter­ested can (re-)read and dis­cuss them. The pre­vi­ous post was Where Ex­pe­rience Con­fuses Physi­cists, and you can use the se­quence_re­runs tag or rss feed to fol­low the rest of the se­ries.

Se­quence re­runs are a com­mu­nity-driven effort. You can par­ti­ci­pate by re-read­ing the se­quence post, dis­cussing it here, post­ing the next day’s se­quence re­runs post, or sum­ma­riz­ing forth­com­ing ar­ti­cles on the wiki. Go here for more de­tails, or to have meta dis­cus­sions about the Rerun­ning the Se­quences se­ries.