Quantum Mechanics I: Interpretations

1. Quantum Mechanics I:Interpretations by Robert Nemiroff Michigan Technological University

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

3. Uncertainty Principle:Interpretations There are MANY interpretations of quantum mechanics, but only a few will be reviewed here: • Copenhagen Interpretation • Many Worlds Interpretation • Ensemble Interpretation • Hidden Variables

4. Uncertainty Principle:Copenhagen Interpretation • Most quoted interpretation convention. • No single statement defines it. • Defining properties sometimes unclear. • Systems described by wave function(s) • Wave functions are probabilistic • particles do not have an exact position • uncertainty principle always holds • Wave functions "collapse" when an observer makes a measurement

5. Uncertainty Principle: Many Worlds Interpretation • Every possible quantum measurement outcome occurs • each outcome is realized in a different universe • these universes do not communicate • together, these universes compose a metaverse • No observer-triggered wave function collapse • therefore different from the Copenhagen interpretation • incorporates "decoherence" instead

6. Uncertainty Principle: Ensemble Interpretation • QM wavefunctions only apply to particle ensembles • does not apply to individual particles • each particle in ensemble is "prepared" the same • supported, at times, by Einstein • avoids some single-particle philosophy debates • can attribute probability to classical ignorance, not QM indeterminancy

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