Is there a double slit experiment that I can perform that will show the photons acting like particles?

Question

I have done many double and single slit experiments where I created clear interference patterns. But one of the amazing things about the double slit is that under certain conditions the wave properties of light go away and the particle properties of light are created. How can I create an experiment where the interference pattern is replaced with a pattern that shows the particle properties of light?

Answer 1

Actually the particle properties of light are there all along, and the pattern would be the same.

To see light as particles in the double-slit experiment, you have to shoot photons individually and see them form the interference pattern dot by dot.

What would make a different pattern though is a detector able to record which slit a photon uses. You would then not get any more interferences, just the sum of two single-slit diffraction patterns.

Answer 2

You can detect the individual photons building up the interference pattern by using a digital camera to record the interference pattern. You then need to place the camera behind the slits and you need to make sure the photo-sites of the sensor are going to be hit no more than a few hundred times. This is because you need to use the highest ISO setting where the dynamic range will be the lowest.

If you use a 1 mw green laser and the entire interference patters covers all the, say, 20 megapixels, then there are about 140 million photons hitting each photo-site per second. If you expose for, say, 1/4000 seconds, you'll still have 35000 photons hitting each photo-site, which is too much. You can reduce the amount by using a neutral density filter. If you use one that reduces the light intensity by a factor of 1000, you'll have on average 35 photons per photo-site per exposure, allowing you to see the discrete steps in intensity at each pixel.

You'll also have to deal with noise and the fact that only a fraction of the photons hitting a photo-site will actually be detected, these factors depend on the quality of the camera.

Answer 3

Sure, you need to detect which slit the photon goes through. In principle you could do it like this:

1. Hang a plate from an apparatus that is robust against transferring momentum to it.
2. Cut two slits into the plate that have splitting on the order of the photon wavelength to set up the regular double slit scenario.
3. Design a very sensitive momentum sensor for the plate (for instance put reflecting mirrors on the ends and set up a laser interferometer)
4. Shoot one photon at a time at the center of your plate, detect which way the plate is kicked due to conservation of momentum.