2. Many Worlds - Many Minds A view of our universe Ingvar Lindgren

3. Einstein Dispute about the interpretation of QM Bohr ”God plays dice” ”God does NOT play dice”

4. ...modern experiments and the discovery of decoherence have shifted the prevailing quantum interpretations away from wave function collapse towards unitary physics,....

5. Copenhagen school Bohr, Heisenberg, Pauli

6. Result ii Wave function  c i  i M Measuring process acc. to Cop. interpret. A measurement is performed by a macroscopic apparatus System is instantaneously and randomly transformed to an eigenstate of the observable. Wave function collapse The probability for a certain result is |c i | 2 ”God plays dice” Max Born’s probalitity interpretation

7. EPR paradox Einstein-Podolsky-Rosen 1935 Hidden variables? Bell’s inequality Two-photon decay J=0 Photons of opposite polarization. Acc. to Cop. interpret. the photons have no specific polarization, before the pol. has been measured. Superposition of states.  c i  i ii The measurement of photon 1 gives it a specific polarization. Then also the polarization of photon 2 will be given.

8. Schrödinger’s cat Radiation from a radioactive material initiates a buttet that kills the cat. Before the observation, the cat is acc. to Copenhagen interpret. in a superposition of dead and alive.

9. Superposition -- entanglement  c i  i Mathematically a state can be expanded in any complete basis set. Entanglement: Coupling of physical states (eigenstates of an observable)‏ Collapse of wave function: Abrupt destruction of entanglement  c i  i ii

10. Problems with the Copenhagen interpretation The measurement process requires an macroscopic observer. The collapse of the wave function does not follow any known laws of physics. Born’s statistical interpretation is an additional assumption that does not follow from the model. Artificial border between micro and macro systems.

12. Entire world evolves accord. to time-dependent Schrödinger eq. Also measuring device treated quantum mechanically (von Neumann)‏ Dropping collapse of wf

13.     c i |S i    0 > No interaction between system and meas. device Measuring device affected by interaction with the system under study    c i |S i  i > No interaction between system and meas. device Interaction between system and meas. device SM SM

14. Everett termed this ”relative-state model” DeWitt introduced around 1970 the term ”Many-worlds interpretation” Observer connected to ONE branch, sees only that branch SM S1M1S1M1 S2M2S2M2 SM S1M1O1S1M1O1 S2M2O1S2M2O1

15. The Everett original model is incomplete. Does not explain the emergence of stable, non-interfering brances Does not explain the emergence of classicality Decoherence has to be considered Why no interference between the branches?

16. Dynamical dislocation of quantum-mechanical entanglements, destruction of quantum coherence Decoherens (W.H. Zurek, H.D. Zeh ~1980)‏ Zurek, Rev. Mod. Phys. 75, 715 (2003)‏ Purely quantum-mechanical phenomenon Caused by interaction by the environment Wojciech Hubert Zurek Dieter Zeh

17. Left alone, strong coherences between the branches Complete entanglement SM S1M1S1M1 S2M2S2M2

18. SM S1M1S1M1 S2M2S2M2 Interaction with environment

19. SM S1M1S1M1 S2M2S2M2 Entanglement with environment reduces entanglement between branches

20. SM S1M1S1M1 S2M2S2M2 Further entanglement with environment reduces further entanglement between branches

21. Eventually development of stable pointer states Not further affected by environment Branches completely decoupled Emergence of classicality SM S1M1S1M1 S2M2S2M2 pointer states stable, decoupled classicality

22. SM S1M1S1M1 S2M2S2M2 Zurek: Einselection environment-induced superselection Preferred states: Independent of initial conditions pointer states stable, decoupled classicality

23. SM S1M1S1M1 S2M2S2M2 This is the measurement process in MWI Different “worlds” - different “minds” Observer in one branch not aware of the other branches No macroscopic observer No collapse Continuous transition to classicality – No cat! pointer states stable, decoupled classicality

24. SM S1M1S1M1 S2M2S2M2 Compare Darwin's theory: Origin of the spicies Survival of the fittest ”Quantum Darvinism” pointer states stable, decoupled classicality

25. SM S2M2S2M2 Copenhagen interpretation: Nature selects randomly ONE branch ”God plays dice”

26. Extra detektor Stern-Gerlach magnet to measure spin orientation Extra detector will destroy interference

27. System (spin) – detector (magnet) – environment (extra detektor) System (spin) – detector (magnet):  =  s + d + e + > +  s - d - e - > |     s + d + > <  s - d - | Density matrix  = |  > <  | = Interference terms  =     s + d + >  +  s - d - > Reduced density matrix for sd system ( =  ij ):  r  =  e = |     s + d + > <  s - d - | No interference

28. H. D. Zeh: The importance of decoherence was overlooked for the first 60 years of quantum theory precisely because entanglement was misunderstood....

29. Quantum-mechanical decoherence has been verified experimentally Zeilinger et al., Nature 401, 680 (1999)‏ Haroche et al, PRL 77, 4887 (1996)‏ Serge HarocheAnton Zeilinger

30. Advantages with Everett-DeWitt model (with decoherence)‏ Schrödinger equation strictly valid. No collapse of wave function. No classical observer needed. No artificial border between micro and macro systems. Decoherence leads to emergence of classicality – No cat states Born’s statistical interpretation follows from the model (Zurek 2005)‏

31. Many experts consider this to be the most – or even the only -- consistent interpretation of mechanics quantum presented so far.

32. Dieter Zeh 2000: The multi-universe interpretation (which should rather be called multi-consciousness interpretation) seems to be the only interpretation of a universal quantum theory (with an exact Schrödinger equation) that is compatible with the way the world is perceived. However, because of quantum non-locality it requires an appropriate modification of the traditional epistemological postulate of psycho-physical parallelism. In this interpretation, the physical world is completely described by Everett's wave function that evolves deterministically (Laplacean). This global quantum state then defines an inde- terministic (hence "branching") succession of states for all observers. Therefore, the world itself appears indeterministic subjective in principle, but largely objective through quantum correlations (entanglement).

33. Dieter Zeh 2000:... the Heisenberg-Bohr picture of quantum mechanics is dead. Neither classical concepts, nor any uncertainty relations, complementarity, observables, quantum logic, quantum statistics, or quantum jumps have to be introduced on a fundamental level.

34. The decoherence leads ‏to disentanglement of entangled states. The branches still exist but are not aware of each other. Personal view

35. Universe – a bifurcations tree

40. Life....... Universe – a bifurcations tree

41. Life....... Homo sapiens Universe – a bifurcations tree

42. Life.......... Homo sapiens I.L. Universe – a bifurcations tree

43. Life....... Homo sapiens....... Probability for Life  Hom.sap.  I.L extremely small.... I.L. Universe – a bifurcations tree

44. Tage Danielssons statistik ”Jag menar, före Harrisburg så var det ju ytterst osannolikt att det som hände i Harrisburg skulle hända, men så fort det hade hänt, rakade ju sannolikheten upp till inte mindre än 100 procent, så det var nästan sant att det hade hänt.”

45. Life....... Homo sapiens....... Probability for Life  Hom.sap.  I.L extremely small.... ”Men när det väl har hänt, är sannolikheten 100 %, och det är nästan sant att det har hänt.” I.L. Universe – a bifurcations tree

46. Life....... Homo sapiens.......... All branches remain – no collapse of wave function I.L. Universe – a bifurcations tree

47. My universe.......... I.L. Life Homo sapiens But each observer can see only one branch – ”Many minds” All branches remain – no collapse of wave function

48. .......... Life Homo sapiens ”Anthropic principle” Looks like a collapse of wave function for each observer I.L. All branches remain – no collapse of wave function My universe But each observer can see only one branch – ”Many minds”

49. Anthropic principle

50. No coincidence that the universe has the properties it has Acc. to anthropic principle universe must have exactly these properties in order for humans to be created and to develop If not, we would not exist and could not worry about it. (Dicke 1961, Brandon Carter, 1973)‏ Brandon Carter

51. A Brief History of Time (1988)‏ (9 mill. copies)‏ Stephen Hawking Universe in a nutshell (2001)‏

52. Hugh Ross: Fingerprint of God Creator and the Cosmos Martin Rees: Before the beginning Barrow-Silk: The left hand of creation

53. The direction of time (5.ed.)‏ Knowledge and the world H. Dieter Zeh

54. Max Tegmark

55. I.L. Interpretation of Quantum Mechanics, http://fy.chalmers.se/~f3ail/ Peter Byrne: The Many Worlds of Hugh Everett, Sci. Amer. Nov. 2007 Stanford Encyclopedia of Philosophy Zurek, Rev. Mod. Phys. 75, 715 ( 2003 )‏ Further reading D. H. Zeh, arXiv:quant-ph Tegmark and Wheeler: 100 years of the Quantum, arXiv:quant-ph/0101077v1 Zurek, Physics Today 44, 36 (1991)