129 research outputs found
Electromagnetically Induced Transparency from a Single Atom in Free Space
We report an absorption spectroscopy experiment and the observation of
electromagnetically induced transparency from a single trapped atom. We focus a
weak and narrowband Gaussian light beam onto an optically cooled Barium ion
using a high numerical aperture lens. Extinction of this beam is observed with
measured values of up to 1.3 %. We demonstrate electromagnetically induced
transparency of the ion by tuning a strong control beam over a two-photon
resonance in a three-level lambda-type system. The probe beam extinction is
inhibited by more than 75 % due to population trapping.Comment: 4 pages, 3 figure
Optical control of the refractive index of a single atom
We experimentally demonstrate the elementary case of electromagnetically
induced transparency (EIT) with a single atom inside an optical cavity probed
by a weak field. We observe the modification of the dispersive and absorptive
properties of the atom by changing the frequency of a control light field.
Moreover, a strong cooling effect has been observed at two-photon resonance,
increasing the storage time of our atoms twenty-fold to about 16 seconds. Our
result points towards all-optical switching with single photons
Bayesian feedback control of a two-atom spin-state in an atom-cavity system
We experimentally demonstrate real-time feedback control of the joint
spin-state of two neutral Caesium atoms inside a high finesse optical cavity.
The quantum states are discriminated by their different cavity transmission
levels. A Bayesian update formalism is used to estimate state occupation
probabilities as well as transition rates. We stabilize the balanced two-atom
mixed state, which is deterministically inaccessible, via feedback control and
find very good agreement with Monte-Carlo simulations. On average, the feedback
loops achieves near optimal conditions by steering the system to the target
state marginally exceeding the time to retrieve information about its state.Comment: 4 pages, 4 figure
Stability of surfaces in the chalcopyrite system
It has been observed previously that the stable surfaces in chalcopyrites are the polar 112 surfaces. We present an electron microscopy study of epitaxial films of different compositions. It is shown that for both CuGaSe2 and CuInSe2 the 001 surfaces form 112 facets. With increasing Cu excess the faceting is suppressed, indicating a lower surface energy of the 001 surface than the energy of the 112 surface in the Cu rich regime, but the 001 surface is higher in energy than the 112 surface in the Cu poor regime. As both surfaces are polar the stabilization is attributed to defect formatio
Unusual mixed solvent supramolecular crystal framework formed of a new tecton-like tetracarboxylic building block
Broken symmetry and the variation of critical properties in the phase behaviour of supramolecular rhombus tilings
The degree of randomness, or partial order, present in two-dimensional
supramolecular arrays of isophthalate tetracarboxylic acids is shown to vary
due to subtle chemical changes such as the choice of solvent or small
differences in molecular dimensions. This variation may be quantified using an
order parameter and reveals a novel phase behaviour including random tiling
with varying critical properties as well as ordered phases dominated by either
parallel or non-parallel alignment of neighbouring molecules, consistent with
long-standing theoretical studies. The balance between order and randomness is
driven by small differences in the intermolecular interaction energies, which
we show, using numerical simulations, can be related to the measured order
parameter. Significant variations occur even when the energy difference is much
less than the thermal energy highlighting the delicate balance between entropic
and energetic effects in complex self-assembly processes
Two-Dimensional 1,3,5-Tris(4-carboxyphenyl)benzene Self-Assembly at the 1-Phenyloctane/Graphite Interface Revisited
International audienceTwo-dimensional (2D) self-assembly of star-shaped 1,3,5-tris(4-carboxyphenyl)benzene molecules is investigated. Scanning tunneling microscopy reveals that this molecule can form three hydrogen-bonded networks at the 1-phenyloctane/graphite interface. One of these structures is close-packed and the two other ones are porous structures, with hexagonal and rectangular cavities. The network with rectangular cavities appears to be the most stable structure
Cavity electromagnetically induced transparency and all-optical switching using ion Coulomb crystals
The control of one light field by another, ultimately at the single photon
level, is a challenging task which has numerous interesting applications within
nonlinear optics and quantum information science. Due to the extremely weak
direct interactions between optical photons in vacuum, this type of control can
in practice only be achieved through highly nonlinear interactions within a
medium. Electromagnetic induced transparency (EIT) constitutes one such means
to obtain the extremely strong nonlinear coupling needed to facilitate
interactions between two faint light fields. Here, we demonstrate for the first
time EIT as well as all-optical EIT-based light switching using ion Coulomb
crystals situated in an optical cavity. Unprecedented narrow cavity EIT feature
widths down to a few kHz and a change from essentially full transmission to
full absorption of the probe field within a window of only ~100 kHz are
achieved. By applying a weak switching field, we furthermore demonstrate nearly
perfect switching of the transmission of the probe field. These results
represent important milestones for future realizations of quantum information
processing devices, such as high-efficiency quantum memories, single-photon
transistors and single-photon gates
Thalidomide influences atherogenesis in aortas of ApoE−/−/LDLR−/− double knockout mice: a nano-CT study
A Mississippian black shale record of redox oscillation in the Craven Basin, UK
Early diagenetic redox oscillation processes have been rarely recognised in the ancient rock record but potentially exert an important control on mineral authigenesis, hydrocarbon prospectivity and supply of metals and/or reduced S as part of associated mineral systems. The upper unit of the Mississippian Bowland Shale Formation is a candidate record of diagenetic redox oscillation processes because it was deposited under a relatively high sediment accumulation rate linked to a large delta system, and under dominantly anoxic and intermittently sulphidic bottom-water conditions. In order to characterise the syngenetic and early diagenetic processes, sedimentological and geochemical data were integrated through the Upper Bowland Shale at three sites in the Craven Basin (Lancashire, UK). Organic matter (OM) comprises a mixture of Type II, II-S, II/III and III OM. ‘Redox zones’ are defined by patterns of Fe-speciation and redox-sensitive trace element enrichment and split into two groups. ‘Sulphidic’ zones (EUX, AN-III, AN-I and AN-IT) represent sediments deposited under conditions of at least intermittently active sulphate-reduction in bottom-waters. ‘Non-sulphidic’ zones (OX-RX, OX-F and OX) represent sediments deposited under non-sulphidic (oxic to ferruginous anoxic) bottom-waters. Operation of a shelf-to-basin ‘reactive Fe’ (FeHR) shuttle, moderated by sea level fluctuation and delta proximity, controlled the position and stability of redoxclines between zones of Fe and sulphate reduction, and methanogenesis. Early diagenetic redoxclines were capable of migration through the shallow sediment column relatively quickly, in response to sea level fluctuation. Preservation of syngenetic and early diagenetic geochemical signals shows redoxclines between Fe and sulphate reduction, and the upper boundary of sulphate-methane transition zone, were positioned within decimetres (i.e., 10 s cm) of seabed. Falling sea level and increasing FeHR supply is recognised as a switch from zones EUX (high sea level), AN-III and ultimately AN-I and AN-IT (low sea level). Zone AN-I defines the operation of ‘redox oscillation’, between zones of Fe and sulphate reduction in shallow porewaters, associated with enhanced degradation of OM and complete dissolution of primary carbonate. Preservation of OM and carbonate, in this system, was a function of changing bottom and pore water redox processes. Redox oscillation operated in a siliciclastic, prodeltaic environment associated with a relatively high sediment accumulation rate and high loadings of labile organic matter and metal oxides. These findings are important for understanding Late Palaeozoic black shales in the context of hydrocarbon and mineral systems
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