Eur. Phys. J. B (2018) 91: 156
https://doi.org/10.1140/epjb/e2018-80716-6

Regular Article

Landauer’s limit and the physicality of information^★

Department of Electrical and Computer Engineering, University of Massachusetts Amherst, Amherst, MA 01003-9292, USA

^a e-mail: anderson@ecs.umass.edu

Received: 19 December 2017
Received in final form: 7 May 2018
Published online: 9 July 2018

Abstract

Landauer’s lower bound on the dissipative cost of information erasure is revisited within a new physical conception of information. The notion of strong physical information is introduced, and the new conception of physical information – observer-local referential (OLR) information – is defined, shown to be strongly physical, and related to other measures that arise in physical information contexts. A generalization of Landauer’s limit is then obtained for OLR information from quantum dynamics and entropic inequalities alone. Specializations of this bound are compared and contrasted to similar bounds under conditions for which they coincide, and important distinctions between seemingly identical bounds expressed in terms of various information measures are discussed. The controversial distinction between Landauer erasure of known and unknown data – and the alleged difference between their respective erasure costs – is then explored via OLR information. This physically grounds and clarifies distinctions between known and unknown data and between unconditional and conditional erasure operations, enables a straightforward physical accounting of associated lower bounds on erasure costs, and illustrates the advantages of OLR information for resolution of controversies related to the dissipative cost of information erasure. Applications of OLR information to determination of irreversibility induced dissipation bounds in more complex computing scenarios are briefly discussed.