From the physical point of view entanglement witnesses (EWs) define a universal tool for
analysis and classification of quantum entangled states. From the mathematical perspective …

The quantum steering ellipsoid of a two-qubit state is the set of Bloch vectors that Bob can
collapse Alice's qubit to, considering all possible measurements on his qubit. We provide an …

Any two-qubit state can be represented geometrically by a steering ellipsoid inside the Bloch
sphere. We extend this approach to represent any block-positive two-qubit operator B. We …

It was conjectured that the structural physical approximation (SPA) of an optimal
entanglement witness is separable (or equivalently, that the SPA of an optimal positive map …

Disproving the conjecture on the structural physical approximation to optimal decomposable
entanglement witnesses - IOPscience Skip to content IOP Science home Accessibility Help …

Numerous work had been done to quantify the entanglement of a two-qubit quantum state,
but it can be seen that previous works were based on joint measurements on two copies or …

We present an analysis of the properties and characteristics of weakly optimal entanglement
witnesses, that is witnesses whose expectation value vanishes on at least one product …

In open quantum systems, it is known that if the system and environment are in a product
state, the evolution of the system is given by a linear completely positive (CP) Hermitian …

We provide a recurrent construction of entanglement witnesses for a bipartite systems living
in a Hilbert space corresponding to 2 N qubits (N qubits in each subsystem). Our …

Any bipartite entanglement witness W can be written as W= c σ I− σ, where σ is a quantum
state, I is the identity matrix, and c σ is a non-negative number. We present a general method …