Whats wrong with concept of "faster than light" information transfer device? (not about technical implementation, just about theory)

Question

Yesterday, while lying in bed, an idea came to me, and I don’t understand why it won’t work?

1. Setup:

   1.1) Two infinite stores of entangled pairs of photons, each connected to a double-slit device.

   1.2) Each of them can emit photons in the same order.

   1.3) The devices are separated by a vast distance (1B light years, as example).

2. Modulation:

   One device modulates a binary signal by toggling the detector on/off, influencing whether an interference pattern appears (wave-like behavior) or disappears (particle-like behavior).

3. Observation:

   At the distant device, a screen and macro-sensor (like a camera) are used to detect changes in the interference pattern to (particle-like and back to wave-like behavior). These changes are interpreted as the binary signal.

What's wrong with this concept?

Answer 1

There isn't enough information given here to answer this question fully, but the short version is that whatever you do at you do for the "modulation" has absolutely no observable effect on anything you can detect at the distant device.

The formal reason for this is the no-communication theorem, which you can read more about on wikipedia, or many other places