Double slit questions

Transcription

1 1) How does the intensity pattern on the screen look for an experiment with light and classical particles respectively? Similarities and differences?

2 Intensity Double slit questions Intensity 1) How does the intensity pattern on the screen look for an experiment with light and classical particles respectively? Similarities and differences? Light Classical particles

3 2) How does the intensity pattern look when you do the experiment with a stream of (many) quantum particles, like electrons, neutrons,?

4 Intensity 2) How does the intensity pattern look when you do the experiment with a stream of (many) quantum particles, like electrons, neutrons,? Quantum particles

5 3) If you instead send in quantum particles towards the slits one by one, what happens to the intensity pattern? How does the pattern evolve when more and more particles are sent in? Why?

6 3) If you instead send in quantum particles towards the slits one by one, what happens to the intensity pattern? How does the pattern evolve when more and more particles are sent in? Why? N=11 N=200 N=6000 N=40000 N=140000

7 4) Is there some place on the screen where the particles never can end up? How can one understand this?

8 Intensity Double slit questions 4) Is there some place on the screen where the particles never can end up? How can one understand this? Ideal case Reality Destructive interference of waves

9 5) What determines where each individual particle will hit the screen? Why?

10 5) What determines where each individual particle will hit the screen? Why? God does not play dice Well, according to (orthodox) quantum mechanics god does! Quantum mechanics only give statistical predictions for measurement outcomes. There is no way to predict exactly where each individual particle hit. Newtons/Maxwells world was deterministic. The quantum world is indeterministic. A lot of discussions related to free will,

11 6) Does the particle go through one of the two slits, through both or through none of them? If possible, how would you describe this using the language of particles and/or waves?

12 6) Does the particle go through one of the two slits, through both or through none of them? If possible, how would you describe this using the language of particles and/or waves? Wave through both slits Particle through one slit Quantum particles are described by probability waves describes both wave and particle properties. Orthodox quantum mechanics: The question is pointless, we should only make predictions for outcomes of measurements!

13 7) What happens when you try to detect/measure through which of the slits the particle went? Why do you think this happens? Do you see any parallels to the story of Schrödingers cat?

14 7) What happens when you try to detect/measure through which of the slits the particle went? Why do you think this happens? Do you see any parallels to the story of Schrödingers cat? When you measure you will see the particle going through one of the two slits By asking a particle question you get a particle answer Interference pattern destroyed Schrödingers cat - Before you look the cat is in a quantum superposition of dead and alive. - When you look you will find it either dead or alive (reduction/collapse).

15 8) What does it mean to detect, or measure, through which slit the particle goes? Can t this measurement be done without disturbing the particle? Why?

16 8) What does it mean to detect, or measure, through which slit the particle goes? Can t this measurement be done without disturbing the particle? Why? Measurement is interaction By looking you modify the quantum particle properties Looking without disturbing works only in the classical world.

17 9) Does it matter who performs the measurement, a conscious observer or a machine? Motivate your conclusion!

18 9) Does it matter who performs the measurement, a conscious observer or a machine? Motivate your conclusion! The only requirement in (orthodox) quantum mechanics: the observer must be a classical object (man or machine).