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Quantum Cheshire Cats

Quantum Cheshire Cats. Y. Aharonov, S. Popescu, D. Rohrlich, P. Skrzypczyk (2012). Quantum Cheshire Cats. Quantum Cheshire Cats. Quantum Cheshire Cats. Quantum weak values. A pre- and post-selected ensemble: The initial state is The final state is. Quantum weak values.

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Quantum Cheshire Cats

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  1. Quantum Cheshire Cats Y. Aharonov, S. Popescu, D. Rohrlich, P. Skrzypczyk (2012)

  2. Quantum Cheshire Cats

  3. Quantum Cheshire Cats

  4. Quantum Cheshire Cats

  5. Quantum weak values A pre- and post-selected ensemble: The initial state is The final state is

  6. Quantum weak values A pre- and post-selected ensemble: The initial state is The final state is measure A “weakly”

  7. Quantum weak values If we measure A “weakly” on an ensemble of systems pre-selected in and post-selected in , the result is the “weak value” : Y. Aharonov, D. Albert and L. Vaidman, PRL60 (1988) 1351

  8. Quantum Cheshire Cats

  9. Quantum Cheshire Cats

  10. Quantum Cheshire Cats “Well! I've often seen a cat without a grin,” thought Alice; “but a grin without a cat! It's the most curious thing I ever saw in all my life!”

  11. Quantum “grin” states “grin +” (left circularly polarized) “grin –” (left circularly polarized)

  12. Quantum position states

  13. Quantum Cheshire Cats

  14. Quantum weak values The weak value of is

  15. Quantum weak values The weak value of is

  16. Quantum weak values The weak value of is

  17. Quantum weak values So, is the Cat in the Left box? It sure is!

  18. Quantum weak values So, is the Cat grinning? It sure is!

  19. Quantum Cheshire Cat The Cat in the Left box, and the Cat is grinning. Hence it is obvious, dear Alice, that the Cat is grinning in the Left box!

  20. Quantum Cheshire Cat The Cat in the Left box, and the Cat is grinning. Hence it is obvious, dear Alice, that the Cat is grinning in the Left box! Obvious but false: the weak value of vanishes!

  21. Quantum weak values The weak value of is

  22. Quantum weak values The weak value of is

  23. Quantum Cheshire Cat The Cheshire Cat is in the Left box, but there is no net grin in the Left box. On the contrary, the only net grin is in the Right box.

  24. Quantum Cheshire Cat

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