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 😅