Inconsistent Histories Revealed by Quantum Measurement

1. Inconsistent Histories Revealed by Quantum Measurement A New Class of Paradoxes and their Implications Avshalom Elitzur and Shahar Dolev Bar-Ilan University

2. Overview: • The Rationale • The three views concerning time • The issue of time-asymmetry and indeterminism • Two types of QM experiments: Spatial and temporal paradoxes • Our strategy • Inconsistent histories? • Back to time

3. The Rationale: • QM challenges our basic notions of space and time. • Therefore, a better understanding of the quantum riddles will come from a deeper account of spacetime. • Conversely, a better understanding of spacetime might emerge from investigating into quantum riddles

4. Three Views of Time: • “Block Universe” • “Extreme Presentism” • “Becoming”

5. The Issue Of Time-Asymmetry And Indeterminism Run Simulation!

6. The Issue Of Time-Asymmetry And Indeterminism

7. The Issue Of Time-Asymmetry And Indeterminism

8. Two Types Of QM Experiments: • Experiments presenting spatial peculiarities: EPR Experiment E-V Experiment

9. Two Types Of QM Experiments: • Experiments presenting temporal peculiarities: HBT Experiment Schrödinger’s cat Delayed Choice

10. x x x x Aharonov’s and Cramer’s proposal • Aharonov’s and Cramer’s unifying theories: • All type-A experiments are in fact type-B experiments. • The problem: Block Universe again. ? ? • Offer • Confirmation • Negotiation • Handshake

11. Our Strategy: • Postpone the Quantum-classical Interaction. • Pursue the bomb idea • This was first taken up by Hardy.

12. Results: • The first result (Hardy, 1992): EPR formed by a single particle in an MZI: • Particles in superpositions (but not entangled) • “Silent” Detector clicks • The particles become entangled

13. Results: • Second result (Hardy, 1992): a quantum mechanical bomb more intriguing than EV • Particle in a superposition • “Silent” Detector clicks • The particle must have “collapsed” into the crossing box • The photon must have gone through the opposite path!

14. Inconsistent Histories? • A new class of paradoxes: When the measurement measures not only a state but an entire evolution, then • indeed sometimes an entire evolution seems to be formed; • sometimes that evolution looks like a Schrödinger cat with a history of a dead cat but traces of a live one.

15. Inconsistent Histories? • Non sequential behavior of the wave function: • Particles in superposition (but not entangled) • “Silent” Detector clicks • The middle particle was measured and found to have “collapsed” into the intersecting box • All other particles returned to their original superposition!

16. Inverse EPR… (Elitzur, Dolev, Zeilinger 2001) … or better call it: RPE

17. Inverse EPR • Particles in superposition (but not entangled) • “Silent” Detector clicks • The particles become entangled

18. Inverse EPR • With an inconsistent history? • To test non-locality, test for Bell Inequality • Use Spin measurement in 3 directions: x, y, and z • Spin x (“which box”) measurement allows only one history for the photon • Consequently, the entanglement disappears

19. Inconsistent Histories? THIS SENTENCE HAS NEVER BEEN WRITTEN :-)

20. Back To Time • Could there be a transactional model in which spacetime itself is subject to dynamics?