I have a train of pulses (with some known time separation between them) and I want to mix two of these (perform an XOR - beam splitter transformation - between them), leaving the rest alone. How do I do this?
If the pulses were separated into different spatial modes I could just take a regular beam splitter and stick the two modes I wanted into it, but how can this be done in time?
Equivalently is there a way to efficiently change the basis of an optical pulse train to the spatial domain?
We can assume the pulses are identical up to a binary phase (which is wy the BS transform will give an XOR).
A restriction is that I won't know very long in advance which modes I want to mix, and it will be given differently each run of the experiment.
It seems like there should be an off-the-shelf thing that does this (some kind of commercial (de)multiplexing device)?