research question: what is the effect of modulation frequency and optical coupling ratio on von neumann entropy, Shannon entropy, bit error rate, mutual information?

methodology: There will be two lasers which will be modulated by an Aurdino to produce bit sequences. A neutral density filter will be applied on top of the lasers to reduce the amount of photos. On the path of one laser beam there will be a quarter wave plate and a half wave plate and on the other there will only be a half wave plate. My reasoning for this is because when i later reconstruct the density matrix for the von Neumann entropy it will be easier to detect the two different beams. Half wave plates and quarter wave plates tend to be very expensive so I will be making it myself. I will link an article at the end which describes how to do so.

The beams will then be combined into a variable beam splitter. These are really expensive so I was testing out other options and a plastic box seems to work just fine... I saw a video reconfirming my belief. I will link it at the end as well. Anyways, I was planning to change the angle of the opening of the box. (will make sense if you see the video.) This is meant to be the 'crosstalk' aspect of my experiment.

Then the beams will continue. I will find out the bit error rate using a SPAD (single photon detector). I will do the same for mutual information. I will measure the shannon entropy in the same way. Lastly for the von Neumann entropy I will measure the intensities at different angles to get the stokes parameters from which I will get the polarization density matrix.

Here are the links:

utube vid: https://youtu.be/P1n3hizj3c4?si=EJAcG6kwxXsObGpe

article: Broadband quarter- and half-wave plates manufactured with cellophane films - ScienceDirect

application: Essentially, I am testing to see whether polarization entropy can be used as an additional diagnostic tool that BER (which is what is conventionally used) overlooks. This can be used to detect changes in signal quality based on the physical qualities of the light which transmits it in quantum communication systems, not solely based on the transmitted bit sequences.

Anyways, any advice on this topic would be greatly welcome such as any additional applications/ resources you would reccomend. Also if there are any blaringly obvious problems that I happened to overlook please let me know.