If you have demonstrated the Hong-Ou-Mandel effect, you might want to convince yourself that both photons really leave the beam splitter in one output and hence you do not see any coincidences anymore (or rather, since the experiment is not perfect, you see a lot less coincidences).
How can we do that? Easy. We add a Hanbury Brown & Twiss setup in one of the outputs (or even in both, if you have 2 quED-HBT). This should look like this:
And in the actual Experiment:
We expect that in the minimum of the Hong-Ou-Mandel dip, we should see a maximum of coincidences between the detectors 2 and 3. The reason being that those are the ones that are behind the beam splitter and if there are two photons at the input of the beam splitter, in about half of the cases they should split up. This is the same idea we always use in the Hanbury-Brown & Twiss measurements.
And this is what we have measured:
The green and purple lines are the coincidences between detector 1 and detector 2 and 3, respectively. You can see the HOM dip there. The white line, however, represents coincidences between detector 2 and 3. Here you see a peak where the other lines show the dip.
What do you need?
- 1 x quED (high rate version advised)
- 1 x quED-HOM (for optimal resolution use motorised version)
- 1 (or 2) x quED-HBT
- 2-Photon Hong-Ou-Mandel Interference
- Single-Photon Interference (Michelson Interferometer) + Hanbury Brown & Twiss
- Franson Interference