Abstract

Recently, Brukner and Zeilinger (Phys. Rev. Lett. 83(17) (2001) 3354) have claimed that the Shannon information is not well defined as a measure of information in quantum mechanics, adducing arguments that seek to show that it is inextricably tied to classical notions of measurement. It is shown here that these arguments do not succeed: the Shannon information does not have problematic ties to classical concepts. In a further argument, Brukner and Zeilinger compare the Shannon information unfavourably to their preferred information measure, I(p), with regard to the definition of a notion of ''total information content.'' This argument is found unconvincing and the relationship between individual measures of information and notions of ''total information content'' investigated. We close by considering the prospects of Zeilinger's Foundational Principle as a foundational principle for quantum mechanics.