Unital quantum operators on the Bloch ball and Bloch region

For one qubit systems, we present a short, elementary argument characterizing unital quantum operators in terms of their action on Bloch vectors. We then show how our approach generalizes to multi-qubit systems, obtaining inequalities that govern when a ``diagonal'' superoperator on the Bloch region is a quantum operator. These inequalities are the n-qubit analogue of the Algoet-Fujiwara conditions. Our work is facilitated by an analysis of operator-sum decompositions in which negative summands are allowed.Comment: Revised and corrected, to appear in Physical Review

The first cyborg and First World War bodies as anti-war propaganda

This article discusses a play published in The Strand Magazine during the First World War which features a cyborg presenting anti-war and pacifist messages, used by The Strand to create anti-German propaganda. The article draws on theories of disability, cyborgs and the posthuman, and from new research on wartime fiction magazines. The importance of the cyborg character, Soldier 241, for the literary history of science fiction is explored by focusing on the relations between the mechanical and the impaired body, and on the First World War as a nexus for technological, surgical and military development. As a cyborg, this character reflects politicized desires that the wartime authorities did not acknowledge: a longing for the end of war, and refusal to countenance a society that rejected the impaired body