Hi, I stumbled upon "http://grad.physics.sunysb.edu/~amarch/" [Broken] about a double slit quantum eraser experiment. Reading it I got the idea that it could be used for faster-than-light communication. The problem is that I couldn't figure out in which way this method would fail (other than being a rather tough nut to crack engineering wise). I would appreciate it if someone could point out where it crashes with theory. Here's the idea: Alice generates a several batches of entangled photons and gives half, one from each pair, to Bob via conventional means. Bob then travels to a nearby star, where he wants to communicate back his findings to Alice as soon as possible. So, at a predetermined time after the Bob arrives, Bob begins to send photons from the first batch through the p path of the detector (as described in the eraser experiment). To encode a zero, he would insert the polarizer, and to encode a 1 he would remove it. Simultaneously, Alice sends her first batch trough the s path of the detector. If she notices an interference pattern, she writes down a 1, else a 0. The problems I see are: a) Keeping the photons entangled and preventing loss, so that the batches are "in sync". b) Some way of counting the number of photons sent into the detector device, so that Alice knows when to move Ds. Or could she just use a regular double slit setup (photographic plate or similar)? Are there any theoretical issues with the above? Or are they just (very hard) engineering challenges? Although the photons have to get to Bob via conventional means, if it could work, wouldn't this for all intents and purposes be a FTL communication device?