4,795 research outputs found
Cosmological Implications of the Fundamental Relations of X-ray Clusters
Based on the two-parameter family nature of X-ray clusters of galaxies
obtained in a separate paper, we discuss the formation history of clusters and
cosmological parameters of the universe. Utilizing the spherical collapse model
of cluster formation, and assuming that the cluster X-ray core radius is
proportional to the virial radius at the time of the cluster collapse, the
observed relations among the density, radius, and temperature of clusters imply
that cluster formation occurs in a wide range of redshift. The observed
relations favor the low-density universe. Moreover, we find that the model of
is preferable.Comment: 7 pages, 4 figures. To be published in ApJ Letter
On the quantumness of correlations in nuclear magnetic resonance
Nuclear Magnetic Resonance (NMR) was successfully employed to test several
protocols and ideas in Quantum Information Science. In most of these
implementations the existence of entanglement was ruled out. This fact
introduced concerns and questions about the quantum nature of such bench tests.
In this article we address some issues related to the non-classical aspects of
NMR systems. We discuss some experiments where the quantum aspects of this
system are supported by quantum correlations of separable states. Such
quantumness, beyond the entanglement-separability paradigm, is revealed via a
departure between the quantum and the classical versions of information theory.
In this scenario, the concept of quantum discord seems to play an important
role. We also present an experimental implementation of an analogous of the
single-photon Mach-Zehnder interferometer employing two nuclear spins to encode
the interferometric paths. This experiment illustrate how non-classical
correlations of separable states may be used to simulate quantum dynamics. The
results obtained are completely equivalent to the optical scenario, where
entanglement (between two field modes) may be present
Hanbury Brown Twiss effect for ultracold quantum gases
We have studied 2-body correlations of atoms in an expanding cloud above and
below the Bose-Einstein condensation threshold. The observed correlation
function for a thermal cloud shows a bunching behavior, while the correlation
is flat for a coherent sample. These quantum correlations are the atomic
analogue of the Hanbury Brown Twiss effect. We observe the effect in three
dimensions and study its dependence on cloud size.Comment: Figure 1 availabl
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