What Every Dog Should Know
  About Quantum Physics
                         
               xp 
                      ...
Quantum Physics




                  ~20 Nobel Prizes
                  For quantum pioneers
Why Should Dogs Care About Quantum
                     Physics?
Three reasons:

     1) Computers
            Semiconduct...
What‟s the Deal with Quantum Physics?
Four essential elements:

       I) Wavefunctions
             Everything in the uni...
Wavefunctions
I) Wavefunctions
     Everything in the universe is
     described by a wavefunction

Mathematical function,...
Electrical Conductors
Electrical properties of materials depend on electron motion:
Electron Waves
Electrons behave like waves
Semiconductor Chips
Control electron properties by
modifying material

Key to making silicon computer chips




 Computer...
Allowed States
II) Allowed States
       Quantum objects are only
       found in specific states

“State”  collection of...
Atomic Spectra
Bohr Model




    Niels Bohr, 1913
Explains light emitted by atoms
        Strange idea, but effective
        Gets hydro...
Lasers
Lasers work using allowed states
   Start with excited atoms


   Emit light, drop down in energy



   Light cause...
Laser Communications
                          First Laser: May 16, 1960
                             “A solution looking ...
Probability
III) Probability
       You can only predict the
       probability of a given state

Wavefunction gives proba...
Sunlight
Temperature of Sun: 10,000,000 degrees

Shines by nuclear fusion:
   Stick 4 protons together, make helium
Sunlight
                        Temperature of Sun: 10,000,000 degrees

                        Shines by nuclear fusion:...
Sunlight
Temperature of Sun: 10,000,000 degrees

Shines by nuclear fusion:
   Stick 4 protons together, make helium
Proble...
Probability is a Problem

              “The theory delivers a lot,
              but hardly brings us closer
            ...
“Physicists are silly…”




      Can never know exactly where thrown
       object will land, only probability
Measurement
IV) Measurement
     An object‟s state is
     indeterminate until you
     measure it

Wavefunction tells you...
Schrödinger‟s Cat




(from http://commons.wikimedia.org/wiki/File:Schrodinger_cat_everret.png )
Schrödinger‟s Cat
Cat is both alive and dead
  AT THE SAME TIME


Invented by Erwin
   Schrödinger to show
   philosophica...
Tennis Experiment
Tennis Experiment




 Find probability distribution with two stripes, one each slit
Electron Experiment
Send electrons at two slits in a barrier:




              Image and video from Hitachi:
            ...
What‟s Going On?

Phenomenon called “Interference”

  Waves from two different sources
    add to give bright and dark spo...
Double Slit
Pattern depends on distance from slits




Get alternating pattern of “bright” and “dark” stripes
Double Slit with Electrons
Electrons behave like waves

  Probability shows the
     effects of interference

BUT: electro...
Double Slit with Electrons
“[A] phenomenon which is
impossible, absolutely
impossible, to explain in any
classical way, an...
More Interference
Double-slit only scratches the
  surface of quantum weirdness

   Interference of molecules
      (C60, ...
What Every Dog Should Know
                About Quantum Physics
Four essential elements, shown in double-slit experiment:...
Schrödinger‟s Dog
The End
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What Every Dog Should Know About Quantum Physics

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A talk given to the IB class from Schenectady high School, 5/24/10.

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What Every Dog Should Know About Quantum Physics

  1. 1. What Every Dog Should Know About Quantum Physics  xp  2 I like cheese Chad Orzel http://scienceblogs.com/principles/
  2. 2. Quantum Physics ~20 Nobel Prizes For quantum pioneers
  3. 3. Why Should Dogs Care About Quantum Physics? Three reasons: 1) Computers Semiconductor chips 2) Telecommunications Lasers, fiber optics 3) Sunlight Quantum physics allows the Sun to shine
  4. 4. 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
  5. 5. 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
  6. 6. Electrical Conductors Electrical properties of materials depend on electron motion:
  7. 7. Electron Waves Electrons behave like waves
  8. 8. Semiconductor Chips Control electron properties by modifying material Key to making silicon computer chips  Computers are Quantum!
  9. 9. 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
  10. 10. Atomic Spectra
  11. 11. Bohr Model Niels Bohr, 1913 Explains light emitted by atoms Strange idea, but effective Gets hydrogen almost perfectly (not as successful with other elements)  Not the full story, but gets started in right direction
  12. 12. Lasers Lasers work using allowed states Start with excited atoms Emit light, drop down in energy Light causes other atoms to emit  Amplification Build up between mirrors
  13. 13. Laser Communications First Laser: May 16, 1960 “A solution looking for a problem…” Gordon Gould, Union „41 One problem it solves: T. Maiman Fiber optic communications Telephone, Internet sent using laser light  Telephones are Quantum!
  14. 14. 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  Some chance of things happening even when they shouldn‟t
  15. 15. Sunlight Temperature of Sun: 10,000,000 degrees Shines by nuclear fusion: Stick 4 protons together, make helium
  16. 16. Sunlight Temperature of Sun: 10,000,000 degrees Shines by nuclear fusion: Stick 4 protons together, make helium Problem: Protons repel each other (unless they‟re really, really close) Temperature needed to get fusion directly: 15,000,000,000 degrees 1,500 times the Sun‟s temperature!
  17. 17. Sunlight Temperature of Sun: 10,000,000 degrees Shines by nuclear fusion: Stick 4 protons together, make helium Problem: need 15,000,000,000 degrees Solution: Quantum Tunneling Small probability of particles passing through impassable barriers Allows enough fusion to power Sun  Sunlight is Quantum!
  18. 18. 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
  19. 19. “Physicists are silly…” Can never know exactly where thrown object will land, only probability
  20. 20. 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
  21. 21. Schrödinger‟s Cat (from http://commons.wikimedia.org/wiki/File:Schrodinger_cat_everret.png )
  22. 22. 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
  23. 23. Tennis Experiment
  24. 24. Tennis Experiment  Find probability distribution with two stripes, one each slit
  25. 25. Electron Experiment Send electrons at two slits in a barrier: Image and video from Hitachi: http://www.hitachi.com/rd/research/em/doubleslit.html
  26. 26. 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 = =
  27. 27. Double Slit Pattern depends on distance from slits Get alternating pattern of “bright” and “dark” stripes
  28. 28. 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
  29. 29. 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
  30. 30. 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
  31. 31. 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
  32. 32. Schrödinger‟s Dog
  33. 33. The End

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