(stupid) question about FTL

here's something I don't understand. and this will seem really stupid and I know I am wrong, so I am not trying to argue something stupid, I just want to get where my understanding fails: I have thought of a method of actually transmitting information FTL and I cannot see during what step it doesn't work. So think of a simple quantum computer that has only one task to compute some basic quantum algorithm or whatever. my understanding is that sometimes, this computation can just break due to accidental decoherence. can that not be used to transmit information? here's my scenario: we have a quantum computer entangled with another quantum computer. I don't care whether that can be created using current tech or anything, just imagine a quantum computer was split in two. then we take one of the halves and fly it across the galaxy 1 light year away. doesn't matter how or anything, and let's assume it doesn't lose coherence. we discuss beforehand that after X time, one person will perform that quantum algorithm on one of the halves, and the other will intentionally decohere it at that exact time discussed beforehand if he wished to send a "True" message, or not do anything if he wishes to send a "False" message. so a simple boolean message sent FTL, and the way it is received is instant: we know what algorithm the computer does and what the input is: if the output is correct = no decoherence = False, if output is wrong or gibberish = decoherence = True. where am I mistaking? and just to make it clear again, I am asking this because I have recently started learning basic stuff about quantum computers and I want to understand what am I misunderstanding. I come from computer science not physics. Thanks submitted by /u/Royal_Plate2092 [link] [comments]