From Einstein To Quantum Cryptography
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The document summarizes a presentation given on January 14, 2012 for AUC Open Day. The presentation covered topics including the first quantum cryptography bank transfer between Vienna City Hall and a bank branch using entangled photons, the wave-particle duality of light and quantum mechanics, Bell's theorem and experiments violating local realism, and applications of quantum cryptography including secure communication using entangled photons. The presentation aimed to explain some counterintuitive aspects of quantum physics.
![ Determinism: “I would always be able to keep my
deterministic faith for fundamental phenomena” (Lorentz)
Causality
Can compute, but what does it mean? “If I am not
satisfied with current state of problem it is because I do not
understand yet physical meaning of its solution. What Heisenberg
has said is mathematically unexceptionable, but the point in
question is that of physical interpretation” (Schrödinger).
“Anschaulichkeit”: “The way Dirac has formulated
Schrödinger’s theory [leads to] a more advanced renunciation of
Anschaulichkeit, a fact very characteristic of symbolic methods in
quantum theory” (Bohr).
AUC Open Day January 14, 2012. SdH](https://image.slidesharecdn.com/fromeinsteintoquantumcryptography-130122141633-phpapp01/85/From-Einstein-To-Quantum-Cryptography-11-320.jpg)
From Einstein To Quantum Cryptography
- 1. AUC Open Day January 14, 2012 Sebastian de Haro
- 2. • First bank transfer encoded via quantum crypto for entangled photons • Information via glass fiber cable from Vienna City Hall to Bank Austria Creditanstalt branch office “Schottengasse”
- 3. Particles or waves? AUC Open Day January 14, 2012. SdH
- 4. http://russherman.com/Talks/FirstThreeMinutes_CollegeDay.pdf AUC Open Day January 14, 2012. SdH
- 5. AUC Open Day January 14, 2012. SdH
- 6. AUC Open Day January 14, 2012. SdH
- 7. AUC Open Day January 14, 2012. SdH
- 8. AUC Open Day January 14, 2012. SdH
- 9. Wave pulse Traveling wave Position well-defined Frequency (and velocity) well-defined Frequency (and velocity) ill-defined Position ill-defined Δ𝑥Δ𝑣 ≥ ℎ/𝑚 Planck’s constant: ℎ = 6,626068 × 10−34 kg m2 /s AUC Open Day January 14, 2012. SdH
- 10. “God does not play dice” AUC Open Day January 14, 2012. SdH
- 11. Determinism: “I would always be able to keep my deterministic faith for fundamental phenomena” (Lorentz) Causality Can compute, but what does it mean? “If I am not satisfied with current state of problem it is because I do not understand yet physical meaning of its solution. What Heisenberg has said is mathematically unexceptionable, but the point in question is that of physical interpretation” (Schrödinger). “Anschaulichkeit”: “The way Dirac has formulated Schrödinger’s theory [leads to] a more advanced renunciation of Anschaulichkeit, a fact very characteristic of symbolic methods in quantum theory” (Bohr). AUC Open Day January 14, 2012. SdH
- 12. 𝑣2 𝑣1 𝑣 = 𝑣1 + 𝑣2 = 0 AUC Open Day January 14, 2012. SdH
- 13. 𝑣2 𝑣1 = 100 m/s 𝑥 = 𝑥1 + 𝑥2 = 0 𝑣 = 𝑣1 + 𝑣2 = 0 AUC Open Day January 14, 2012. SdH
- 14. 𝑣2 𝑣1 = 100 m/s • No influences faster than light. • Conclusion: particle must have velocity before we measure it. • Violation of Δ𝑥Δ𝑣 ≥ ℎ/𝑚 • Therefore quantum mechanics is an incomplete theory. 𝑣= 𝑣1 + 𝑣2 = 0 AUC Open Day January 14, 2012. SdH
- 15. Faster-than-light interaction is not needed. We only have correlations. Entanglement: particles correlated and system behaves as a whole rather than sum of parts. Bell’s theorem (‘64): If independent particles had defined velocities before measured, this implies certain inequality which QM violates. Experiment confirms quantum mechanics (Aspect ‘82). AUC Open Day January 14, 2012. SdH
- 16. EPR with spin: + ↓ ↑ AUC Open Day January 14, 2012. SdH
- 17. Four possible states: ↑↑ 1 ↑↓+↓↑ 𝑠=1 2 ↓↓ 1 ↑↓−↓↑ 𝑠=0 2 AUC Open Day January 14, 2012. SdH
- 18. Record: 144 km in La Palma, Tenerife AUC Open Day January 14, 2012. SdH
- 19. 1 ↑↓−↓↑ 2 ↑= 1 ↓= 0 110100010 110100010 Share a randomly generated key Big Questions in Science, fall 2011. SdH, AUC 19
- 20. AUC Open Day January 14, 2012. SdH
- 21. Can be used for secure communication. Eavesdropper destroys correlations.
- 22. Photons: AUC Open Day January 14, 2012. SdH
- 24. Interference means change No possible ‘unvisible’ eavesdropper Applications: Banking Confident information Collaboration fundamental research with industry (and government). Key feature: entanglement (“spooky action at a distance”) AUC Open Day January 14, 2012. SdH
- 25. Counter-intuitive aspects: “If you are not confused by quantum physics then you haven’t really understood it.” (Niels Bohr) “I think I can safely say that nobody understands quantum mechanics.” (Richard Feynman). After WWII: “Shut up and calculate”. Imposed by increasing numbers of students: “Such classroom numbers, Berkeley’s department chair exclaimed to his dean, were ‘a disgrace and should not be tolerated at any respectable university’… The larger the class, the less time spent talking through the big issues.” (David Kaiser) AUC Open Day January 14, 2012. SdH
- 26. Central to most of modern physics. Key experiments and formalism. Interpretation. AUC Open Day January 14, 2012. SdH