Recently, Kayumov [Lobachevskii J. Math. 38 (2017), pp. 466–468] obtained a sharp estimate for the n n -th truncated area functional normalize...

We discuss a generalization to 2 qubits of the standard Bloch sphere representation for a single qubit, in the framework of Hopf fibrations of high dimensional spheres by lower dimensional spheres. The single qubit Hilbert space is the 3-dimensional sphere S. The S base space of a suitably oriented S Hopf fibration is nothing but the Bloch sphere, while the circular fibres represent the qubit o...