I think it was my graduate quantum mechanics textbook (Gottfried and Yan), I read a description of the double slit experiment. It first described how the act of measuring which slit the particle goes through destroys the interference pattern. Then it went on to give a detailed exposition. It gave a example in which the detector at the slits writes to a computer hard drive which slit the particle passed through. Then it said that even if you leave everything the same, and have the detector interact with the particle at the slit, you can still create or destroy the interference pattern by disconnecting or connecting the hard drive at a location arbitrarily far from the experiment. I want to read about this again but I am not sure where I read it. I got a copy of Gottfried and Yan but it does not have the thing I want in it. It is a different version than I used in grad school as well, and I'm no even sure this is where I read what I'm looking for. Does anyone know where I can find or read about something like this: how even putting the detector to detect the particle does not destroy the interference pattern if it is not allowed to write the result to the HDD.
References appreciated, thanks!