1,240 research outputs found
A Note on the Radiative and Collisional Branching Ratios in Polarized Radiation Transport with Coherent Scattering
We discuss the implementation of physically meaningful branching ratios
between the CRD and PRD contributions to the emissivity of a polarized
multi-term atom in the presence of both inelastic and elastic collisions. Our
derivation is based on a recent theoretical formulation of partially coherent
scattering, and it relies on a heuristic diagrammatic analysis of the various
radiative and collisional processes to determine the proper form of the
branching ratios. The expression we obtain for the emissivity is
, where and
are the emissivity terms for the redistributed and
partially coherent radiation, respectively, and where "f.s." implies that the
corresponding term must be evaluated assuming a flat-spectrum average of the
incident radiation
Quantum error correction may delay, but also cause, entanglement sudden death
Dissipation may cause two initially entangled qubits to evolve into a
separable state in a finite time. This behavior is called entanglement sudden
death (ESD). We study to what extent quantum error correction can combat ESD.
We find that in some cases quantum error correction can delay entanglement
sudden death but in other cases quantum error correction may cause ESD for
states that otherwise do not suffer from it. Our analysis also shows that
fidelity may not be the best measure to compare the efficiency of different
error correction codes since the fidelity is not directly coupled to a state's
remaining entanglement.Comment: 3 figure
Entanglement invariant for the double Jaynes-Cummings model
We study entanglement dynamics between four qubits interacting through two
isolated Jaynes-Cummings hamiltonians, via the entanglement measure based on
the wedge product. We compare the results with similar results obtained using
bipartite concurrence resulting in what is referred to as "entanglement sudden
death". We find a natural entanglement invariant under evolution demonstrating
that entanglement sudden death is caused by ignoring (tracing over) some of the
system's degrees of freedom that become entangled through the interaction.Comment: Sec. V has largely been rewritten. An error pertaining to the
entanglement invariant has been corrected and a correct invariant valid for a
much larger set of states have been found, Eq. (25
Salt harvesting
Saltworks (other terms: salterns, saltponds, solar ponds) are man-made hypersaline systems where table salt or halite (NaCl, sodium chloride) is harvested. Salt production in the Guadiana River estuary is based on solar evaporation of sea water. In other areas, salt is obtained from solid state or brine mining.
Saltworks using sea water are usually located in low coastal areas, allowing gravitational filling of ponds during the high tides. Evaporative salt production is restricted to geographical areas where this process is favoured by combined action of wind, solar radiation, low rain rates, and high temperatures. Hence, the Mediterranean and part of the European Atlantic coastal areas fulfil these conditions, particularly during
the summer months where the evaporation greatly exceeds precipitation.info:eu-repo/semantics/publishedVersio
Detecting non-locality in multipartite quantum systems with two-body correlation functions
Bell inequalities define experimentally observable quantities to detect
non-locality. In general, they involve correlation functions of all the
parties. Unfortunately, these measurements are hard to implement for systems
consisting of many constituents, where only few-body correlation functions are
accessible. Here we demonstrate that higher-order correlation functions are not
necessary to certify nonlocality in multipartite quantum states by constructing
Bell inequalities from one- and two-body correlation functions for an arbitrary
number of parties. The obtained inequalities are violated by some of the Dicke
states, which arise naturally in many-body physics as the ground states of the
two-body Lipkin-Meshkov-Glick Hamiltonian.Comment: 10 pages, 2 figures, 1 tabl
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