I'm watching Leonard Susskind's online QM lectures, and in it he talks about the double slit experiment. He says that if the particle leaves a "mark", allowing you tell which slit it went through, (for example a "1" vs a "0" on a computer read out) this destroys the interference pattern. But I'm curious, does the "mark" have to permanent? For example if the particle, traveling through one slit, causes a dial inside an empty room to twitch then return to normal, would that destroy the interference pattern? My thinking is that, since information is never destroyed, the twitch of the dial is still 'recorded' in the room, and recoverable, in some sense. if you want me to find the exact lecture and post the video, I can.