We set up the quED and the Michelson Interferometer add-on quED-MI as usual:
We start with the Single Photon Interference effect as before:
The quED-MI is designed in such a way that the polarisation of the photons at the input of the interferometer is diagonal (i.e. 45° between horizontal and vertical). Now we add polarisers in the two arms of the interferometer, one horizontal, one vertical. This affects the interference:
This can be interpreted in the following way: At the output of the interferometer, you can determine by the polarisation of the photon, which of the two possible paths it has taken (so-called “which-way” or “welcher-Weg” information). Thus, the interference is destroyed.
Now, we add a third polariser at the output of the interferometer. This is what happens:
The interference re-appears. Do you know why it is called the “quantum eraser”?
What do you need?
The three polarisers are integrated into the quED-MI, you can swing them in and out.