In the experiment setup picture of the Delayed choice quantum eraser, photons reach D0 and shows a pattern, before its quantum entangled counterparts reach one of D1, D2, D3, or D4. The pattern differs based on what happens at the beam splitters (BSa and BSb) and whether the which-path information is lost.
What if, instead of installing beam splitters BSa and BSb, we install either pure glass panels or pure silver mirrors. Now imagine we place the splitter part of the setup light-years away from earth, with an astronaut who can decide if she wants to put 2 mirrors or 2 glass panels at BSa and BSb. By shooting photons and observing the patterns on D0 on earth, we could instantly tell which decision the astronaut has made. She can then expand this further, encode any information into bits, and achieve FTL communication.
It will be something like: we keep shooting photons at D0 and keep seeing interference pattern, until one day we go, "yep, it starts to look like a diffraction pattern now, she must have switched the panels moments ago!"
Since no information can travel FTL, I'm sure my idea is flawed, but what's wrong with it?
