Quantum Illusions and Time Joan Vaccaro K K

Quantum Illusions and Time Joan Vaccaro K K GU 2007 Quantum Illusions and Time 1

Contents Quantum States Many Worlds Many Times Quantum States Photons (particles of light) • polarisation of E (electric field): two orthogonal directions y x E z GU 2007 Quantum Illusions and Time 2

Contents Quantum States Many Worlds Many Times • arbitrary polarisation y x E z • superpositions placement of “one thing on top of another” y • measurement y x E x 50% z E z PBS GU 2007 Quantum Illusions and Time y x E z 50% 3

Contents Quantum States Many Worlds Many Times • superposition of two positions y x opaque absorber with 2 slits upper E d z lower • verifying the superposition y x interference pattern E z photons pile up here one at a time but NOT here need many photons for verification GU 2007 Quantum Illusions and Time 4

Contents Quantum States Many Worlds Many Times Experiments Young photons electrons 1802 Young 1926 Davisson, Germer & Thomson atoms 1930 Estermann & Stern neutrons 1945 Wollan & Shull bucky balls 2002 Zeilinger virus? bacteria? flea? cat? people? Thomson Shull Zeilinger GU 2007 Quantum Illusions and Time 5

Contents Quantum States Many Worlds Many Times Many Worlds …first a bit of history… • 1920’s: treatment of radioactive decay radioactive atom possible tracks paths Pa( ) of single particle cloud chamber Tr( 1), Pa( 1) Tr( ) & Tr( 2), Pa( 2) Tr( 3), Pa( 3) Tr( 4), Pa( 4) but only one track per particle is seen GU 2007 Quantum Illusions and Time 6

Contents Quantum States Many Worlds Many Times Copenhagen Interpretation: • 1927: Bohr and Heisenberg in Copenhagen when experimenter looks at cloud chamber its state collapses Tr( 1), Pa( 1) Tr( 2), Pa( 2) Tr( 3), Pa( 3) Tr( 4), Pa( 4) see only one track GU 2007 Quantum Illusions and Time 7

Contents Quantum States Schrödinger’s Cat 00: 00 12 9 Many Worlds Many Times radioactive atom + Geiger detector 3 6 GU 2007 Quantum Illusions and Time 8

Contents Quantum States Schrödinger’s Cat 09: 30 12 Many Worlds Many Times radioactive atom + Geiger detector 9 6 cat dies GU 2007 Quantum Illusions and Time hammer trips and breaks vial of poison 9

Contents Quantum States Many Worlds Schrödinger’s Cat radioactive atom + Geiger detector 00: 15 12 9 Many Times 3 hammer trips and breaks vial of poison 6 cat dies Partial decay leads to superposition state until experimenter looks inside box and state collapses 50% chance hi kitty GU 2007 Quantum Illusions and Time oh no… OR 50% chance 10

Contents Quantum States Many Worlds Many Times I don’t like it and I’m sorry I ever had anything to do with it. collapse is not described by any dynamical process (with forces, potentials etc. ) Schrödinger 50% chance hi kitty GU 2007 Quantum Illusions and Time oh no… OR 50% chance 11

Contents Quantum States Everett 1957 (50 th Many Worlds Many Times anniversary year) • applying quantum mechanics to universe (cosmology) • no external observers (experimenters) to collapse state We need new toy example • don’t know how to treat “no life process” (dead) and “life process” (alive) as physical states GU 2007 Quantum Illusions and Time 12

Contents Quantum States Many Worlds Many Times The cat that may (or may not) be fed 00: 00 12 9 3 6 GU 2007 Quantum Illusions and Time 13

Contents Quantum States Many Worlds Many Times The cat that may (or may not) be fed 09: 30 12 9 3 6 GU 2007 Quantum Illusions and Time 14

Contents Quantum States Many Worlds Many Times The cat that may (or may not) be fed 00: 15 12 9 3 6 Why don’t we see this superposition? GU 2007 Quantum Illusions and Time 15

Contents Quantum States Many Worlds Many Times This is what happens when we look… here kitty-kitty… GU 2007 Quantum Illusions and Time 16

Contents Quantum States Many Worlds Many Times This is what happens when we look… there you are you’re so hungry you’ve over eaten …so how do we see superpositions GU 2007 Quantum Illusions and Time 17

Contents Quantum States Many Worlds Many Times The dropped cat experiment (with catchers) - how to “see” a superposition interference probability GU 2007 Quantum Illusions and Time 18

Contents Quantum States Many Worlds Many Times The dropped cat experiment (with catchers) - how to “see” a superposition interference probability GU 2007 Quantum Illusions and Time 19

Contents Quantum States Many Worlds Many Times The dropped cat experiment (with catchers) - how to “see” a superposition Parameters d = 0. 1 m x = 1 m m = 10 kg L = 1067 m probability t = 1026 y interference d x GU 2007 Quantum Illusions and Time L 20

Contents Quantum States Many Worlds Many Times we never even try to do this kind of experiment - need control (& disentangle atom… from cat etc. ) - but, importantly, need to repeat it many times to build up interference pattern separate “worlds” evolve… you’ve fat! here’s food $ $$$ the poor but happy world the rich but sad world the perception of “one single world” is an illusion GU 2007 Quantum Illusions and Time 21

Contents Quantum States Many Worlds Many Times David Pegg’s quantum theory of time • canonical approach to quantising gravity • Wheeler-de. Witt - equation: - universe is in a stationary state Pegg, J. Phys. A 24, - no motion – frozen dynamics 3031 (1991). - energy is well known (zero) prob. X prob. P • Heisenberg uncertainty principle X if you know position X well, momentum P is uncertain “ “ energy E “ time T “ “ P time in the universe must be uncertain GU 2007 Quantum Illusions and Time 22

Contents Quantum States Many Worlds Many Times • use new set of axes – each axis represents a different time state of the universe axes chosen to make projections all equal 3 2 1 1 2 3 4 5 History vector – totality of reality – state at all times GU 2007 Quantum Illusions and Time 23

Contents Quantum States Many Worlds Many Times • divide universe into 2 parts: Clock + Rest clock must have equally spaced energy levels R C orthogonal clock states 1 M M+1 P find interval where Clock and Rest are separate and non-interacting • rewrite interval in terms of orthogonal clock states GU 2007 Quantum Illusions and Time 24

Contents Quantum States M M+1 R 1 C Many Worlds Many Times P R 2 R 3 RP R • the dynamics of Rest can be written in terms of the time parameter t defined by Clock: t = Rn+1 Rn Rn t Schrödinger’s equation for dynamics GU 2007 Quantum Illusions and Time Rn t Rn 25

Contents R 1 Quantum States R 2 Many Worlds Many Times R 3 RP C R we live at these different times the perception of “one present” is an illusion this illusion is on par with the single world illusion GU 2007 Quantum Illusions and Time 26

Contents Quantum States Many Worlds Many Times Puzzle: how does our perception of travelling in time arise? R 1 R 2 these states of Rest are non-orthogonal Rm-1 R R 3 RP so can’t be sure which one we are in Rm Rm+1 • this gives a connection between different states of Rest • but the connection is the same in both directions! GU 2007 Quantum Illusions and Time 27

Contents Quantum States Many Worlds Many Times Puzzle: why do we travel in one direction in time? • anti-particles are the time reversed versions of particles time gamma ray photons electron e antielectron e+ space • all anti-particle and particle pairs are time symmetric except for Kaons (K mesons) GU 2007 Quantum Illusions and Time 28

Contents Quantum States Many Worlds Many Times Neutral kaons K 0 have a lifetime of less than 10 6 s. Decay paths: positron antimatter e+ pion neutrino K 0 e+ + + K 0 e + + + (more likely) electron pion antineutrino • equal number of K 0 and K 0 are found to yield different numbers of e+ and e • violation of CP & T symmetry (CERN 1998) t R 1 K 0 matter R 2 K 0 short lifetime antimatter K 0 R 3 + e matter RP K 0 long lifetime asymmetric GU 2007 Quantum Illusions and Time 29

Contents Quantum States R 1 t Many Worlds R 2 RP K 0 long lifetime K 0 short lifetime Rm-1 R 3 Many Times only unsure of which state in the “future” we are in Rm Rm+1 Kaons appear to be responsible for us travelling through time!!! GU 2007 Quantum Illusions and Time 30

Contents Quantum States Many Worlds Many Times Conclusion Many worlds: we exist in many worlds but have the illusion (and pleasures) of only one - but somewhere we are having a really good time Many times: we exist at many times but have the illusion of only one present which marches steadily toward to our demise! - but consoled by knowing we still exist at earlier times RIP Free will: even our perception of free will is an illusion – we cant change the future because we already exist there (hopefully) - but we can enjoy the illusion GU 2007 Quantum Illusions and Time 31