My original thought experiment from a couple years ago was: could you create one of those laptop screen protectors where the polarization encoding was a kind of one-time pad so that only you can see the screen with a special set of glasses. So many optical effects are quantum mechanical wave interference stuff, so I have always thought of using optical effects to make it hard for classical computers to decode things. How all of this plays out in practice would be serious research endeavours i’d imagine 😅

I know you can do it by just removing the polarizer and putting it on your glasses like this: But it should definitely be possible to just replace your screen with a non standard filter that requires the right glasses filter to see so its even more obscure. Now the real prize would be if theres a way to make it so sensitive or multi layered so that it's not feasible to brute force the encoding. I don't see much of a market for this tho. Anyone this worried about physical privacy should be worried about digital instead.