nt - p h / 03 12 15 5 v 1 1 8 D ec 2 00 3 Nonlocality and information flow : The approach of Deutsch and Hayden

Deutsch and Hayden claim to have provided an account of quantum mechanics which is particularly local, and which clarifies the nature of information transmission in entangled quantum systems. In this paper, a perspicuous description of their formalism is offered and their claim assessed. It proves essential to distinguish, as Deutsch and Hayden do not, between two ways of interpreting the formalism. On the first, conservative , interpretation, no benefits with respect to locality accrue that are not already available on either an Everettian or a statistical interpretation ; and the conclusions regarding information flow are equivocal. The second, ontological, interpretation, offers a framework with the novel feature that global properties of quantum systems are reduced to local ones; but no conclusions follow concerning information flow in more standard quantum mechanics.