# Variations of double slit experiment

1. Jun 8, 2012

### igorcov

Hi,

Have there been done variations of double slit experiment, particularly I'm interested in following scenarios:
1. Three slits instead of 2. (Would expect the same behaviour of wave interference)
2. An observer is installed at one of the three slits. (Again, wave interference should be present?)
3. Double slit with observer in one slit, followed by other panel with 2 slits without observer.

Thanks,

2. Jun 8, 2012

### Simon Bridge

Yep - every variation you can think of has been tried.
Particularly the three-slit experiments:
http://arstechnica.com/science/2010/07/born-rules-quantum-mechanics-survives-triple-slit-test/
... the article makes a mistake by asserting that the photon flows through all the slits in some way.

Your observer interacts with the system in some way - to detect 100% of the photons through one slit, for example, it has to block the slit completely - changing the nature of the experiment.

I still think Feynman gives the best description of how this works in his lay lecture series.

1. yes
2. depends on the setup - I'd expect 2-slit interference to dominate but less bright.
3. depends on the setup - but more complicated. You'd have to sum over all paths through the entire setup.

3. Jun 8, 2012

### DougW

Another question I have always wondered about, has there ever been speculation or research into whether probability has a plank value? What I mean is that anything with a probability of less than 1/6.6 X 10^34 would not exist in our universe. If every other 'measurable' feature of the universe has a planck floor, why wouldn't probability?

4. Jun 8, 2012

### Simon Bridge

iirc: probability does not work like that and neither does the plank length.
You'd have to figure out how the uncertainty principle applies to probability.
You want to go into depth - I'd suggest you start your own thread instead of hijacking someone elses.