Efficient nonlinear witnessing of non-absolutely separable states with lossy detectors

Abstract

Entangled states are undoubtedly an integral part of various quantum information processing tasks. On the other hand, absolutely separable states which cannot be made entangled under any global unitary operations are useless from the resource theoretic perspective, and hence identifying non-absolutely separable states can be an important issue for designing quantum technologies. Here we report that nonlinear witness operators provide significant improvements in detecting non-absolutely separable states over their linear analogs, by invoking examples of states in various dimensions. We also address the problem of closing detection loophole and find critical efficiency of detectors above which no fake detection of non-absolutely separable (non-absolutely positive partial transposed) states is possible.

9 pages, 6 figures

References in corpus (11)

• Entanglement detection
• Optimal entanglement witnesses based on local orthogonal observables
• Determining lower bounds on a measure of multipartite entanglement from few local observables
• Detection Loophole in Bell experiments: How post-selected local correlations can look non-local
• Optimal two-qubit tomography based on local and global measurements: Maximal robustness against errors as described by condition numbers
• Entanglement witnesses and a loophole problem
• Accessible nonlinear entanglement witnesses
• Nonlinear entanglement witnesses, covariance matrices and the geometry of separable states
• Iterations of nonlinear entanglement witnesses
• Positive reduction from spectra
• Nonlinear Improvement of Qubit-qudit Entanglement Witnesses

Cited by in corpus (4)

• Absolute fully entangled fraction from spectrum
• Maximum entanglement of mixed symmetric states under unitary transformations
• Resource Theory of Non-absolute Separability
• Measurement-device-independent nonlinear entanglement witnesses