We obtain a mathematically simple characterization of all functionals coinciding with the von Neumann reduced entropy on pure states based on the Khinchin–Faddeev axiomatization of Shannon entropy and give a physical interpretation of the axioms in terms of entanglement.
We explore and develop the mathematics of the theory of entanglement measures. After a careful review and analysis of definitions, of preliminary results, and of connections between conditions on entanglement measures, we prove a sharpened version of a uniqueness theorem which gives necessary and sufficient conditions for an entanglement measure to coincide with the reduced von Neumann entropy on pure states. We also prove several versions of a theorem on extreme entanglement measures in the case of mixed states. We analyze properties of the asymptotic regularization of entanglement measures proving, for example, convexity for the entanglement cost and for the regularized relative entropy of entangle ment.
Entanglement is well understood concept for distinguishable particles. However fundamental particles are inherently indistinguishable and when they occupy orthogonal modes, i.e. have orthogonal wave functions, they are effectively distinguishable. Thus there should exist a formulation for entanglement which works in the generic case, i.e. even when wave functions overlap. To achieve this, we consider R\`{e}nyi entropies which are measurable quantities. Outcomes of such measurements for a generic case are conjectured in terms of R\`{e}nyi entropies of spatial regions in a field theory. To leading order naive quantum mechanical answers are reproduced. Corrections depend on overlap of wave functions and exhibit novel features. In a generic case the Von Neumann entropy computed from these R\`{e}nyi entropies is argued to be a measure of entanglement of pure states and a formula for this is conjectured in terms of Von Neumann entropies of spatial regions in field theory. It seems, due to the corrections it is possible for the entanglement to exceed maximal quantum mechanical value, e.g. log2 for a single qubit.
Consider a system consisting of n d-dimensional quantum particles and an arbitrary pure state $|\ensuremath{\Psi}〉$ of the whole system. Suppose we simultaneously perform complete von Neumann measurements on each particle. The Shannon entropy of the outcomes' joint probability distribution is a functional of the state $|\ensuremath{\Psi}〉$ and of n measurements chosen for each particle. Denote $S[\ensuremath{\Psi}]$ the minimum of this entropy over all choices of the measurements. We show that $S[\ensuremath{\Psi}]$ coincides with the entropy of entanglement for bipartite states. We compute $S[\ensuremath{\Psi}]$ for some special multipartite states: the hexacode state ∣H〉(n=6,d=2) and the determinant states ∣Detn〉(d=n). The computation yields S[H]=4log2 and S[Detn]=log(n!). Counterparts of the determinant state defined for d<n are also considered.
Abstract We introduce new entanglement measures on the set of density operators on tensor product Hilbert spaces. These measures are based on the greatest cross norm on the tensor product of the sets of trace class operators on Hilbert space. We show that they satisfy all the basic requirements on entanglement measures discussed in the literature, including convexity, invariance under local unitary operations and non-increase under local quantum operations and classical communication. In the second part of this paper we discuss the uniqueness theorem for entanglement measures. We obtain a mathematically simple characterization of all functionals coinciding with the von Neumann reduced entropy on pure states based on the Khinchin-Faddeev axiomatization of Shannon entropy and give a physical interpretation of the axioms in terms of entanglement. We also discuss the uniqueness theorem in the operational approach and argue that the standard argument in favor of the uniqueness theorem for entanglement measures is not fully conclusive and that further axioms have to be added to the list of postulates. 1