4,701 research outputs found
Secondary Star Formation in a Population III Object
We explore the possibility of subsequent star formation after a first star
forms in a Pop III object, by focusing on the radiation hydrodynamic (RHD)
feedback brought by ionizing photons as well as H2 dissociating photons. For
the purpose, we perform three-dimensional RHD simulations, where the radiative
transfer of ionizing photons and H2 dissociating photons from a first star is
self-consistently coupled with hydrodynamics based on a smoothed particle
hydrodynamics method. As a result, it is shown that density peaks above a
threshold density can keep collapsing owing to the shielding of H2 dissociating
radiation by an H2 shell formed ahead of a D-type ionization front. But, below
the threshold density, an M-type ionization front accompanied by a shock
propagates, and density peaks are radiation hydrodynamically evaporated by the
shock. The threshold density is dependent on the distance from a source star,
which is for the source distance of 30pc. Taking into
consideration that the extent of a Pop III object is pc and
density peaks within it have the density of cm, it is
concluded that the secondary star formation is allowed in the broad regions in
a Pop III object.Comment: 4pages, 2 figures, submitted to Ap
Extracting Information from Qubit-Environment Correlations
Most works on open quantum systems generally focus on the reduced physical
system by tracing out the environment degrees of freedom. Here we show that the
qubit distributions with the environment are essential for a thorough analysis,
and demonstrate that the way that quantum correlations are distributed in a
quantum register is constrained by the way in which each subsystem gets
correlated with the environment. For a two-qubit system coupled to a common
dissipative environment , we show how to optimise interqubit
correlations and entanglement via a quantification of the qubit-environment
information flow, in a process that, perhaps surprisingly, does not rely on the
knowledge of the state of the environment. To illustrate our findings, we
consider an optically-driven bipartite interacting qubit system under the
action of . By tailoring the light-matter interaction, a
relationship between the qubits early stage disentanglement and the
qubit-environment entanglement distribution is found. We also show that, under
suitable initial conditions, the qubits energy asymmetry allows the
identification of physical scenarios whereby qubit-qubit entanglement minima
coincide with the extrema of the and entanglement
oscillations.Comment: 4 figures, 9 page
Correlations in optically-controlled quantum emitters
We address the problem of optically controlling and quantifying the
dissipative dynamics of quantum and classical correlations in a set-up of
individual quantum emitters under external laser excitation. We show that both
types of correlations, the former measured by the quantum discord, are present
in the system's evolution even though the emitters may exhibit an early stage
disentanglement. In the absence of external laser pumping,we demonstrate
analytically, for a set of suitable initial states, that there is an entropy
bound for which quantum discord and entanglement of the emitters are always
greater than classical correlations, thus disproving an early conjecture that
classical correlations are greater than quantum correlations. Furthermore, we
show that quantum correlations can also be greater than classical correlations
when the system is driven by a laser field. For scenarios where the emitters'
quantum correlations are below their classical counterparts, an optimization of
the evolution of the quantum correlations can be carried out by appropriately
tailoring the amplitude of the laser field and the emitters' dipole-dipole
interaction. We stress the importance of using the entanglement of formation,
rather than the concurrence, as the entanglement measure, since the latter can
grow beyond the total correlations and thus give incorrect results on the
actual system's degree of entanglement.Comment: 11 pages, 10 figures, this version contains minor modifications; to
appear in Phys. Rev.
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