What Every Dog Should Know About Quantum Physics
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The document explains fundamental concepts of quantum physics, highlighting four key elements: wavefunctions, allowed states, probability, and measurement. It discusses how quantum objects exist in indeterminate states until measured and presents the double-slit experiment as a demonstration of interference and randomness in quantum behavior. Notable physicists like Niels Bohr and Albert Einstein are cited, illustrating both the effectiveness and philosophical implications of quantum mechanics.
![Double Slit with Electrons
“[A] phenomenon which is
impossible, absolutely
impossible, to explain in any
classical way, and which has
in it the heart of quantum
mechanics. In reality, it
contains the only mystery.”
-- Richard Feynman](https://image.slidesharecdn.com/homeschool-100322182441-phpapp01/85/What-Every-Dog-Should-Know-About-Quantum-Physics-23-320.jpg)
What Every Dog Should Know About Quantum Physics
- 1. What Every Dog Should Know About Quantum Physics xp 2 I like cheese Chad Orzel http://scienceblogs.com/principles/
- 3. Quantum Physics ~20 Nobel Prizes For quantum pioneers
- 5. What’s the Deal with Quantum Physics? Four essential elements: I) Wavefunctions Everything in the universe is described by a wavefunction II) Allowed States Quantum objects are only found in specific states III) Probability You can only predict the probability of a given state IV) Measurement An object’s state is indeterminate until you measure it
- 6. Wavefunctions I) Wavefunctions Everything in the universe is described by a wavefunction Mathematical function, describes properties of object Put in position and time Get out what’s going on Has both particle and wave properties Detect at specific position like particle Function extends over space like wave
- 7. Allowed States II) Allowed States Quantum objects are only found in specific states “State” collection of properties position, velocity, energy, momentum, etc. Only certain special states are allowed NEVER find object with other properties Property that gives quantum physics its name “quantum” = “how much” in Latin
- 9. Bohr Model Niels Bohr, 1913 Explains light emitted by atoms Strange idea, but effective Gets hydrogen almost perfectly Other elements don’t work as well, but better than any other method
- 10. Bohr Orbits and Waves Wave behavior explains Bohr states Allowed orbits are a whole number of wavelengths in circumference Electron wavefunction ends in the same place it starts Need wave nature to get allowed states (Complete theory doesn’t have orbits, but this gets the basic idea)
- 11. Probability III) Probability You can only predict the probability of a given state Wavefunction gives probability of each of the allowed states Can’t say definitely where a quantum object will be located Outcome of a single experiment is completely random
- 12. Probability is a Problem “The theory delivers a lot, but hardly brings us closer to the secret of the Old One. I for one am convinced that He does not throw dice.” -- Albert Einstein, letter to Max Born,1926
- 13. “Physicists are silly…” Can never know exactly where thrown object will land, only probability
- 14. Measurement IV) Measurement An object’s state is indeterminate until you measure it Wavefunction tells you probability Until you measure it, the object is in ALL possible states, AT THE SAME TIME
- 16. Schrödinger’s Cat Cat is both alive and dead AT THE SAME TIME Invented by Erwin Schrödinger to show philosophical problem with quantum physics Situation seems completely ridiculous BUT IT’S TRUE
- 18. Tennis Experiment Find probability distribution with two stripes, one each slit
- 19. Electron Experiment Send electrons at two slits in a barrier: Image and video from Hitachi: http://www.hitachi.com/rd/research/em/doubleslit.html
- 20. What’s Going On? Phenomenon called “Interference” Waves from two different sources add to give bright and dark spots Peak + Peak = Bigger Peak Peak + Valley = Nothing = =
- 21. Double Slit Pattern depends on distance from slits Get alternating pattern of “bright” and “dark” stripes
- 22. Double Slit with Electrons Electrons behave like waves Probability shows the effects of interference BUT: electrons detected as particles One at a time, at single spots on screen Each electron must pass through BOTH slits at SAME TIME
- 23. Double Slit with Electrons “[A] phenomenon which is impossible, absolutely impossible, to explain in any classical way, and which has in it the heart of quantum mechanics. In reality, it contains the only mystery.” -- Richard Feynman
- 24. More Interference Double-slit only scratches the surface of quantum weirdness Interference of molecules (C60, at right) “Quantum Eraser” Quantum Zeno Effect Entanglement and Teleportation “Spooky action at a distance” etc, etc,… Huge variety of weird stuff involving quantum physics
- 25. What Every Dog Should Know About Quantum Physics Four essential elements, shown in double-slit experiment: I) Wavefunctions Electrons (particles) show interference (waves) II) Allowed States Each slit defines a state III) Probability Where each electron lands is random IV) Measurement Each electron goes through BOTH slits at once
- 29. The End