Characterization and properties of weakly optimal entanglement witnesses

Recurrent construction of optimal entanglement witnesses for 2N-qubit systems

Optimal entanglement criterion for mixed quantum states.

We develop a strong and computationally simple entanglement criterion. The criterion is based on an elementary positive map Phi which operates on state spaces with even dimension N > or = 4. It is shown that Phi detects many entangled states with a positive partial transposition (PPT) and that it leads to a class of optimal entanglement witnesses. This implies that there are no other witnesses ...

Detecting three-qubit bound MUB diagonal entangled states via Nonlinear optimal entanglement witnesses

One of the important approaches to detect quantum entanglement is using linear entanglement witnesses (EW s). In this paper, by determining the envelope of the boundary hyper-planes defined by a family of linear EW s, a set of powerful nonlinear optimal EW s is manipulated. These EW s enable us to detect some three qubits bound MUB (mutually unbiased bases) diagonal entangled states, i.e., the ...

Is absolute separability determined by the partial transpose?

The absolute separability problem asks for a characterization of the quantum states ρ ∈ Mm ⊗Mn with the property that UρU† is separable for all unitary matrices U. We provide evidence that ρ is absolutely separable if and only if UρU† has positive partial transpose for all unitary matrices U. In particular, we show that many well-known separability criteria are unable to detect entanglement in ...

Teleportation via an Entangled Coherent Channel and Decoherence Effect on This Channel

We study an entangled two-mode coherent state within the framework of2×2-dimensional Hilbert space. We investigate the problem of quantum teleportation ofa superposition coherent state via an entangled coherent channel. By three differentmeasures with the titles ``minimum assured fidelity (MASF)”, ``average teleportationfidelity” and ``optimal fidelity (f)” we study the ...