1927 Solvay Conference

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Κλειώ Βασιλόπουλος
8 χρόνια πριν
Προβολές:

1 I. Kominis

2 1927 Solvay Conference Heisenberg Schrödinger Ehrenfest Pauli Bragg Debye Planck Dirac Curie Lorentz Brillouin Compton Born Einstein Bohr

The New Quantum Revolution Gedanken experiments that were puzzling the founders of quantum physics in 1920 s are now real experiments performed in the lab.

3 The New Quantum Revolution Gedanken experiments that were puzzling the founders of quantum physics in 1920 s are now real experiments performed in the lab. The most counter- intuitive concepts of quantum physics are used to develop new technology Quantum Coherence Quantum Entanglement Quantum Non-locality Quantum Uncertainty Quantum Computation Quantum Communication Quantum Cryptography Quantum Sensors

4 1st Quantum Principle Physical reality is irreducibly random God does not play dice

5 1 st Quantum Question How does structure emerge from quantum randomness? or How do we harness quantum reality to produce technology?

6 Quantum Technologies Magnetic Resonance Imaging Photonics Semiconductor Electronics NMR Protein Structure Drug Design Spins Lasers Photons Superconductivity Electrons

7 Quantum Information Processing Quantum Computing Quantum Communications Quantum Cryptography Qubits realized with Electrons Photons Spins

8 Light as electromagnetic wave James Clerk Maxwell ( )

9 Light as a stream of photons Photomultiplier Tube

10 Beam Splitter I in I t I t = I r = I in 2 I r

11 Beam splitter with single photons P 1 P 2 P 3

12 Irreducible quantum randomness The only prediction quantum physics can make is that the probability that the photon will be reflected or transmitted is 1/2. Call Detector A click = 0 Call Detector B click = 1 Repea4ng the experiment many 4mes, we get a inexhaus4ble sequence of quantum random bits :

13 Irreducible quantum randomness The fundamental difference of quantum randomness from classical randomness is that the lager can in principle be reduced to certainty. The former cannot.

14 Hidden variables Hidden-variable theories were introduced to explain quantum randomness. For example, do photons have a reflection-gene or a transmission-gene? If they do, detector B should never fire. However, it does fire with probability 1/4. Hidden-variable theories have been disproved by experiment. Quantum randomness is real.

15 Particle or wave? Young s Double Slit Experiment What is measured at the observation screen is the intensity of incident light, I(x) = E(x) 2 Since E(x) = E 1 (x) + E 2 (x) I(x) = I 1 + I 2 + 2Re{E 1 E 2 * }

16 Young s Double Slit Experiment with particles

17 Quantum Principles Which-path information If any kind of information about the photon path can be retrieved the interference pattern is lost. Complementarity Visibility of interference pattern Knowledge of particle s position Determinism/Randomness The deterministic development of the interference pattern is an ensemble average The detection point of a single particle is fundamentally unpredictable Contextuality If we attempt to measure particle nature, it is a particle. If we attempt to measure wave nature, it is a wave Objective reality is not the classical concept of localized particle or wave, but a multitude of possibilities

18 Mach-Zender Interferometer P A = P B = 1 2 Wrong!!

19 Quantum superposition principle The fundamental principle of quantum physics ψ 1 ψ 2 If and are possible states of the quantum system, then the quantum superposition ψ = α ψ 1 + β ψ 2 is also a possible physical state, where α and β are complex numbers called amplitudes. If a physical event can be realized in many indistinguishable ways P = α 1 + α If a physical event can be realized in many distinguishable ways P = P 1 + P

20 Optics arrangement for Mach-Zender interferometer

21 Optics arrangement for BEC

22 Spin precession in a magnetic field Για τα πρωτόνια 42 MHz/T

23 NPL NBS-1 NBS Rabi introduces atomic beam clock 1955 Essen-Parry (UK) develop the first cesium beam clock with stability 1 s in 300 years 1967 Time switches from astronomical to atomic 1999 Laser cooling clock, stability 1s σε 20,000,000 years NBS-5 NBS-6 NIST-F1

Navigation then and now: GPS 24 δορυφόροι,

24 Navigation then and now: GPS 24 δορυφόροι, τουλάχιστο 4 ορατοί από κάθε σηµείο στη γη. Κάθε δορυφόρος έχει 2 ατοµικά ρολόγια. Μεγάλη ακρίβεια (σταθερότητα) στη µέτρηση χρόνου, άρα Ακρίβεια στην τοποθεσία ~ µερικά m Εφαρµογές: ναυσιπλοϊα, χαρτογραφία, χρονισµός

25 Nuclear magnetic resonance 1952 Nobel Prize in Physics Felix Bloch. (Stanford, USA) Edward Purcell (Harvard, USA) Για την ανάπτυξη νέων µεθόδων και µετρήσεων ακρίβειας πυρηνικού µαγνητισµού.

26 NMR & MRI

27 Quantum physics of spin 100 % πάνω 100 % κάτω 50 % πάνω 50 % κάτω

28 Two spins - entanglement 100 % πάνω και τα δύο 100 % κάτω και τα δύο 50 % πάνω και τα δύο 50 % κάτω και τα δύο

29 Entanglement & quantum computers

30 Classical versus quantum correlations ψ = 1 2 ( + ) ψ = 1 2 ( + )

31 States of matter Temperature plasma gas liquid solid Bose Einstein CondensaBon

32 Superconductivity Superconductivity was discovered by Kamerlingh- Onnes in 1911 in Mercury (Hg) having T c 4 K. Mercury has passed into a new state which on account of its extraordinary electrical properties can be called the superconducting state H. Kamerlingh-Onnes Dependence of Resistance on Temperature

33 Superconducting technology MRI Scanner Human Brain MRI Large magnetic fields (> 1T) are needed to get a high Magnetic Resonance Imaging (MRI) signal Large currents necessary > 1000A Heat dissipation RI 2, coils will melt. With superconducting coils, R=0.

34 Temperature scale for laser cooling Laser Cooling

35 Two Nobel prizes for laser cooling & BEC experiments Ψύξη Ατόµων µε Laser 1997 Nobel Prize in Physics T v BEC BEC = 10 nk. 1 mm/s S. Chu (Stanford, USA) C. Cohen- Tannoudji (ENS, France) W. Phillips (NIST, USA) Για την ανάπτυξη µεθόδων ψύξης και παγίδευσης ατόµων µε laser. T v D D = 122 µk. 10 cm/s 2001 Nobel Prize in Physics E. Cornell (JILA, USA) W. KeGerle (MIT, USA) C. Wieman (JILA, USA) Για την επίτευξη συµπύκνωσης Bose-Einstein σε ατµούς αλκαλικών ατόµων.

Technology for quantum information Manipulation of single atoms and single photons

36 Why bother? Atom Laser 1. New states of matter BEC, Optical Lattices 2. New Technology Atom Lasers, gyroscopes, gravity gradiometers 3. Technology for quantum information Manipulation of single atoms and single photons 4. Precision measurements High accuracy atomic clocks 5. Difficult and exciting experiments!!!! Atomic Fountain Clock

37 Bose-Einstein condensation Bose Bose and Einstein predicted the condensation in 1925, it was realized experimentally in Einstein Atom laser is for atoms what the laser is for photons.

38 Laser cooling and trapping of single ions 1989 Nobel Prize in Physics H. Dehmelt (U. Washington, USA) W. Paul (U. Bonn, Germany) Για την ανάπτυξη µεθόδων παγίδευσης ιόντων. Τεχνολογία Υλοποίησης Κβαντικών Υπολογιστών Απόλυτος Ελεγχος της Κβαντικής Κατάστασης Απόλυτος Ελεγχος Αλληλεπιδράσεων Ιδανική Μόνωση από την Επίδραση του Περιβάλλοντος και άρα Μεγάλος Χρόνος Ζωής Κβαντικών Καταστάσεων

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