Single Photon Dual Slit Demonstartion

[alan sailer]

I have wanted to do a recreation of the classic quantum mechanics demo that show single photons
going through a dual slit can create a classic interference pattern.

Making the set-up did take some time but was reasonably straightforward. The source was a low power HeNe laser.
It goes through a rotatable variable attenuator and two fixed attentuators and then hits the dual slit. At the output
of the slit is a dielectric bandpass filter at 633nm (improves signal to noise ratio) and then into the detector, an old
Hamamatsu image intensifier. The output of this goes into a low light CMOS video camera.

It was easy to see that the set-up worked buy using a camera to integrate the output of the video camera. But I
wanted to see the photon hits add up in real time. I tried a few astrophotography stacking programs but they did
not show real time stacking. After asking about real time stacking on an astro website I was pointed to SharpCap.

It turned out to do the job. After some help from Robin, the programmer of SharpCap I was able to get a good enough
output which I videoed using a Nikon DSLR. Stacking is not integrating but it does work.

As I kind of expected getting software to do the job was more time consuming and frustrating than the mechanical set-up.
Here is a link to my Flickr site showing the video along with my best attempt to narrate what is happening.

https://www.flickr.com/photos/8763834@N02/53334653284

It's kind of fun to do these experiments even though I am finding nothing new. This one was especially neat because
after all is said and done, I have no idea (nor does anyone else) how this can possibly happen. One photon at a time
and you get an interference pattern. Real magic...

Cheers.

[klugesmith]

 Very nice work there, Alan.   The video with narration does the job.   
The demonstration may be traditional, but will always be thought-provoking.

Its reproduction is a most respectable challenge.  Can you show us pictures of your setup?

My optical demonstrations lately have been much more primitive, e.g. diffraction by periodic grids in household objects:
inkjet printer ribbons, fine wire mesh from fuel filters & drip irrigation filters, perforated sheets in coffee filter funnels.
https://highvoltageforum.net/index.php?topic=1894.msg14172#msg14172

[alan sailer]

I'll could publish a photo but honestly it is just a bunch of PVC fittings pounded together. With a bare HeNe on one side.
I've seen pictures of other single photons and it is quite similar, tubes all taped together. Keeping it dark inside is the goal, not pretty.

Cheers.