Q UANTUM M ECHANICS I: I NTERPRETATIONS by Robert Nemiroff Michigan Technological University

Physics X: About This Course Pronounced "Fiziks Ecks" Reviews the coolest concepts in physics Being taught for credit at Michigan Tech o Michigan Tech course PH4999 o Aimed at upper level physics majors o Light on math, heavy on concepts o Anyone anywhere is welcome No textbook required o Wikipedia, web links, and lectures only

U NCERTAINTY P RINCIPLE : I NTERPRETATIONS I NTERPRETATIONS There are MANY interpretations of quantum mechanics, but only a few will be reviewed here: Copenhagen Interpretation Many Worlds Interpretation Ensemble Interpretation Hidden Variables

U NCERTAINTY P RINCIPLE : C OPENHAGEN I NTERPRETATION C OPENHAGEN I NTERPRETATION Most quoted interpretation convention. No single statement defines it. o Defining properties sometimes unclear. Systems described by wave function(s) Wave functions are probabilistic o particles do not have an exact position o uncertainty principle always holds Wave functions "collapse" when an observer makes a measurement

U NCERTAINTY P RINCIPLE : M ANY W ORLDS I NTERPRETATION M ANY W ORLDS I NTERPRETATION Every possible quantum measurement outcome occurs o each outcome is realized in a different universe o these universes do not communicate o together, these universes compose a metaverse No observer-triggered wave function collapse o therefore different from the Copenhagen interpretation o incorporates "decoherence" insteaddecoherence

U NCERTAINTY P RINCIPLE : E NSEMBLE I NTERPRETATION E NSEMBLE I NTERPRETATION QM wavefunctions only apply to particle ensembles o does not apply to individual particles o each particle in ensemble is "prepared" the same o supported, at times, by Einstein o avoids some single-particle philosophy debates o can attribute probability to classical ignorance, not QM indeterminancy

U NCERTAINTY P RINCIPLE : H IDDEN V ARIABLES H IDDEN V ARIABLES Uncertainty caused by untracked complexity Universe classical but influenced by unseen variables o not unlike matter before atoms discovered Once endorsed by Einstein o Origin of "God does not play dice." phrase Fundamentally different than standard QM uncertainty o universe completely deterministic allows a "first mover" type God Might demand faster than light communication Bell realized HV makes different statistical predictions o QM found right, HV wrong by modern tests