5,301 research outputs found
Exploring the framework of assemblage moment matrices and its applications in device-independent characterizations
In a recent work [Phys. Rev. Lett. 116, 240401 (2016)], a framework known by
the name of "assemblage moment matrices" (AMMs) has been introduced for the
device-independent quantification of quantum steerability and measurement
incompatibility. In other words, even with no assumption made on the
preparation device nor the measurement devices, one can make use of this
framework to certify, directly from the observed data, the aforementioned
quantum features. Here, we further explore the framework of AMM and provide
improved device-independent bounds on the generalized robustness of
entanglement, the incompatibility robustness and the incompatibility weight. We
compare the tightness of our device-independent bounds against those obtained
from other approaches. Along the way, we also provide an analytic form for the
generalized robustness of entanglement for an arbitrary two-qudit isotropic
state. When considering a Bell-type experiment in a tri- or more-partite
scenario, we further show that the framework of AMM provides a natural way to
characterize a superset to the set of quantum correlations, namely, one which
also allows post-quantum steering.Comment: 17 pages, 6 figures. Comments welcome
Hierarchy in temporal quantum correlations
Einstein-Podolsky-Rosen (EPR) steering is an intermediate quantum correlation
that lies in between entanglement and Bell non-locality. Its temporal analogue,
temporal steering, has recently been shown to have applications in quantum
information and open quantum systems. Here, we show that there exists a
hierarchy among the three temporal quantum correlations: temporal
inseparability, temporal steering, and macrorealism. Given that the temporal
inseparability can be used to define a measure of quantum causality, similarly
the quantification of temporal steering can be viewed as a weaker measure of
direct cause and can be used to distinguish between direct cause and common
cause in a quantum network.Comment: 10 pages, 3 figure
Examining non-locality and quantumcoherent dynamics induced by acommon reservoir
If two identical emitters are coupled to a common reservoir, entanglement can be generated during the decay process. When using Bell's inequality to examine the non-locality, however, it is possible that the bound cannot be violated in some cases. Here, we propose to use the steering inequality to examine the non-locality induced by a common reservoir. Compared with the Bell inequality, we find that the steering inequality has a better tolerance for examining non-locality. In view of the dynamic nature of the entangling process, we also propose to observe the quantum coherent dynamics by using the Leggett-Garg inequalities. We also suggest a feasible scheme, which consists of two quantum dots coupled to nanowire surface plasmons, for possible experimental realization
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