Fundamental thermodynamic limits in memory preservation


Once written, any memory is doomed to loose its content after some time, if no action is taken. In modern computers, to avoid memory losses, a refresh procedure is periodically performed. In this paper we present theoretical and experimental study of sub-k_BT system to evaluate the minimum energy required to preserve one bit of information over time. Two main conclusions are drawn: i) You can keep your memory for free: the energetic cost to preserve information for a fixed time duration with a given error probability can be arbitrarily reduced if the refresh procedure is performed often enough. ii) You cannot keep it forever: the Heisenberg uncertainty principle sets an upper bound on the memory lifetime.