The fundamental difference between logical and thermodynamic irreversibilities, or, Why Landauer's result cannot be a physical principle

Abstract

Landauer's "principle" claims that erasing one bit of information necessarily dissipates at least Tln2 of heat into the surroundings, making a possibly logically irreversible operation also thermodynamically irreversible. It is commonly accepted that this result is a fundamental principle of physics that definitively establishes the link between information and energy. Here we show that this result cannot be general. In fact it comes: 1) from a confusion between logical and thermodynamic irreversibilities and between logical and thermodynamic states, which is reminiscent of the classic Gibbs' paradox about the joining of two volumes of the same gas; and 2) from two unnecessary constraints imposed on the erase procedure. Clarifying these points permits: to dissociate the notions of logical and thermodynamic irreversibilities; to invalidate Landauer's result as being a general physical principle; and to open the door to hardware implementations allowing erasure to follow a thermodynamically reversible, or at least quasistatic, path.