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AUC Open Day January 14, 2012
Sebastian de Haro
• 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”
Particles or waves?
AUC Open Day January 14, 2012. SdH
http://russherman.com/Talks/FirstThreeMinutes_CollegeDay.pdf AUC Open Day January 14, 2012. SdH
AUC Open Day January 14, 2012. SdH
AUC Open Day January 14, 2012. SdH
AUC Open Day January 14, 2012. SdH
AUC Open Day January 14, 2012. SdH
AUC Open Day January 14, 2012. SdH
Traveling wave Frequency (and velocity) well-defined
Position ill-defined
Wave pulse Position well-defined
Frequency (and velocity) ill-defined
Δ𝑥Δ𝑣 ≥ ℎ/𝑚
Planck’s constant: ℎ = 6,626068 × 10−34 kg m2/s
AUC Open Day January 14, 2012. SdH
“God does not play dice”
AUC Open Day January 14, 2012. SdH
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
𝑣 = 𝑣1 + 𝑣2 = 0
𝑣1 𝑣2
AUC Open Day January 14, 2012. SdH
𝑣1 = 100 m/s 𝑣2
𝑥 = 𝑥1 + 𝑥2 = 0 𝑣 = 𝑣1 + 𝑣2 = 0
AUC Open Day January 14, 2012. SdH
𝑣1 = 100 m/s 𝑣2
𝑣 = 𝑣1 + 𝑣2 = 0
• No influences faster than light. • Conclusion: particle must have
velocity before we measure it. • Violation of • Therefore quantum mechanics is
an incomplete theory.
Δ𝑥Δ𝑣 ≥ ℎ/𝑚
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
EPR with spin:
AUC Open Day January 14, 2012. SdH
↓ ↑ +
Four possible states:
AUC Open Day January 14, 2012. SdH
1
2↑↓+↓↑
↑↑
1
2↑↓−↓↑
↓↓
𝑠 = 1
𝑠 = 0
Record: 144 km in La Palma, Tenerife
AUC Open Day January 14, 2012. SdH
Big Questions in Science, fall 2011. SdH, AUC 19
Share a randomly generated key
↑= 1 ↓= 0
1
2↑↓−↓↑
110100010 110100010
AUC Open Day January 14, 2012. SdH
Can be used for secure communication. Eavesdropper destroys correlations.
Photons:
AUC Open Day January 14, 2012. SdH
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
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
Central to most of modern physics.
Key experiments and formalism.
Interpretation.
AUC Open Day January 14, 2012. SdH