Hi. I hope this is the right forum for the question. Landauer's principle says that the erasure of one bit of information (1 or 0) requires kBTln2 of heat production. When he talks about erasure, it means "resetting back to 0 (or 1)" after measuring. He says something along "this is needed as to not to bias the device". I guess this means "for the device to perform a measure, it needs to previously be in a given state". So that if you need to measure 0's and 1's, it intrinsically needs to be restored to 0 before each new measure. Why?