1,415 research outputs found
Electromagnetically Induced Transparency in strongly interacting Rydberg Gases
We develop an efficient Monte-Carlo approach to describe the optical response
of cold three-level atoms in the presence of EIT and strong atomic
interactions. In particular, we consider a "Rydberg-EIT medium" where one
involved level is subject to large shifts due to strong van der Waals
interactions with surrounding Rydberg atoms. We find excellent agreement with
much more involved quantum calculations and demonstrate its applicability over
a wide range of densities and interaction strengths. The calculations show that
the nonlinear absorption due to Rydberg-Rydberg atom interactions exhibits
universal behavior
Excitation transport through Rydberg dressing
We show how to create long range interactions between alkali-atoms in
different hyper-fine ground states, allowing coherent electronic quantum state
migration. The scheme uses off resonant dressing with atomic Rydberg states,
exploiting the dipole-dipole excitation transfer that is possible between
those. Actual population in the Rydberg state is kept small. Dressing offers
large advantages over the direct use of Rydberg levels: It reduces ionisation
probabilities and provides an additional tuning parameter for life-times and
interaction-strengths. We present an effective Hamiltonian for the ground-state
manifold and show that it correctly describes the full multi-state dynamics for
up to 5 atoms.Comment: 22 pages + 6 pages appendices, 8 figures, replaced with revised
version, added journal referenc
Two-dimensional Rydberg gases and the quantum hard squares model
We study a two-dimensional lattice gas of atoms that are photo-excited to
high-lying Rydberg states in which they interact via the van-der-Waals
interaction. We explore the regime of dominant nearest neighbor interaction
where this system is intimately connected to a quantum version of Baxter's hard
squares model. We show that the strongly correlated ground state of the Rydberg
gas can be analytically described by a projected entangled pair state that
constitutes the ground state of the quantum hard squares model. This
correspondence allows us to identify a first order phase boundary where the
Rydberg gas undergoes a transition from a disordered (liquid) phase to an
ordered (solid) phase
Newton's cradle and entanglement transport in a flexible Rydberg chain
In a regular, flexible chain of Rydberg atoms, a single electronic excitation
localizes on two atoms that are in closer mutual proximity than all others. We
show how the interplay between excitonic and atomic motion causes electronic
excitation and diatomic proximity to propagate through the Rydberg chain as a
combined pulse. In this manner entanglement is transferred adiabatically along
the chain, reminiscent of momentum transfer in Newton's cradle.Comment: 4 pages, 3 figures. Revised versio
Adiabatic entanglement transport in Rydberg aggregates
We consider the interplay between excitonic and atomic motion in a regular,
flexible chain of Rydberg atoms, extending our recent results on entanglement
transport in Rydberg chains [W\"uster et al., Phys.Rev.Lett 105 053004 (2010)].
In such a Rydberg chain, similar to molecular aggregates, an electronic
excitation is delocalised due to long range dipole-dipole interactions among
the atoms. The transport of an exciton that is initially trapped by a chain
dislocation is strongly coupled to nuclear dynamics, forming a localised pulse
of combined excitation and displacement. This pulse transfers entanglement
between dislocated atoms adiabatically along the chain. Details about the
interaction and the preparation of the initial state are discussed. We also
present evidence that the quantum dynamics of this complex many-body problem
can be accurately described by selected quantum-classical methods, which
greatly simplify investigations of excitation transport in flexible chains
The effects of cognitive styles on naive impetus theory application degrees of pre-service science teachers
Cataloged from PDF version of article.The purpose of this study was to determine whether there is a relationship
between pre-service science teachers’ Field Dependent or Field Independent (FD/FI) cognitive
styles and the application of degrees of naive impetus theory. The sample consisted of 122 preservice
science teachers (97 females and 25 males) who were enrolled in the Introductory
Physics course required by the Science Education program. Data were collected in two
successive years, after the completion of the required Introductory Physics undergraduate
courses, in 2008 and 2009. The Group Embedded Figure Test and Impetus Theory
Application Test (a two-tier-type test) were administered to assess the FD/FI tendency of
students and to determine the degree students applied the naïve impetus theory, respectively.
Initial results showed that a majority of students had made use of the native impetus theory
repeatedly. The results also indicated that the degree to which students applied the naïve
impetus theory was statistically related to their FD/FI cognitive styles. The findings of this
research showed that there existed a statistically significant difference between the FI and FD
students’ degree of applying the naïve impetus theory in favor of FI students. However, the test
score gap between FI and FD students remained almost constant regardless of the testing
instruments utilized in this study
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