On superqubits

We first reconsider the mathematical background of superqubit theory and describe important peculiarities of superspaces and supermatrices which are usually out of attention. Then we study states in super Hilbert spaces using super-bra/super-ket formalism in details. The qubit (qudit) and superqubit (superqudit) are defined as linear spans in the corresponding Hilbert subspaces. A new kind of superqubit carring the odd parity is introduced. The multi-superqubit states are studied, and the superconcurrence which distinguishes separable states is proposed.