A home made double slit experiment with a twist! By using a polarizing sheet -- like your sunglasses -- and very careful placement, we can encode the "which path information" in the photons. Watch the video to see how we can use a third polarizer to then erase this information and recover the original interference pattern. Albeit with a lot of imperfections!

Join to see how we can recreate a pretty crazy physics experiment with nothing more than polarizers, rubber erasers, and clothes pegs.

Write up available here!

We have since used this as a demonstration for six clubs days for the SFU Physics Student Association, and upgraded the laser mount to include a frame for the slits t be placed. A future version of this experiment will be 3D printed with slots for a collimating lens, slits, and filters; and maybe also a lens to magnify the beam for short-throw demonstrations. Please be safe with lasers if you try to create this demo, its lots of fun!