320 research outputs found
Efficient qubit detection using alkali earth metal ions and a double STIRAP process
We present a scheme for robust and efficient projection measurement of a
qubit consisting of the two magnetic sublevels in the electronic ground state
of alkali earth metal ions. The scheme is based on two stimulated Raman
adiabatic passages (STIRAP) involving four partially coherent laser fields. We
show how the efficiency depends on experimentally relevant parameters: Rabi
frequencies, pulse widths, laser linewidths, one- and two-photon detunings,
residual laser power, laser polarization and ion motion.Comment: 14 pages, 15 figure
Ramsey interferometry with oppositely detuned fields
We report a narrowing of the interference pattern obtained in an atomic
Ramsey interferometer if the two separated fields have different frequency and
their phase difference is controlled. The width of the Ramsey fringes depends
inversely on the free flight time of ground state atoms before entering the
first field region in addition to the time between the fields. The effect is
stable also for atomic wavepackets with initial position and momentum
distributions and for realistic mode functions.Comment: 6 pages, 6 figure
Three level atom optics via the tunneling interaction
Three level atom optics (TLAO) is introduced as a simple, efficient and
robust method to coherently manipulate and transport neutral atoms. The
tunneling interaction among three trapped states allows to realize the spatial
analog of the stimulated Raman adiabatic passage (STIRAP), coherent population
trapping (CPT), and electromagnetically induced transparency (EIT) techniques.
We investigate a particular implementation in optical microtrap arrays and show
that under realistic parameters the coherent manipulation and transfer of
neutral atoms among dipole traps could be realized in the millisecond range.Comment: 5 pages, 6 figure
Select pyrimidinones inhibit the propagation of the malarial parasite, Plasmodium falciparum
Plasmodium falciparum, the Apicomplexan parasite that is responsible for the most lethal forms of human malaria, is exposed to radically different environments and stress factors during its complex lifecycle. In any organism, Hsp70 chaperones are typically associated with tolerance to stress. We therefore reasoned that inhibition of P. falciparum Hsp70 chaperones would adversely affect parasite homeostasis. To test this hypothesis, we measured whether pyrimidinone-amides, a new class of Hsp70 modulators, could inhibit the replication of the pathogenic P. falciparum stages in human red blood cells. Nine compounds with IC50 values from 30 nM to 1.6 μM were identified. Each compound also altered the ATPase activity of purified P. falciparum Hsp70 in single-turnover assays, although higher concentrations of agents were required than was necessary to inhibit P. falciparum replication. Varying effects of these compounds on Hsp70s from other organisms were also observed. Together, our data indicate that pyrimidinone-amides constitute a novel class of anti-malarial agents. © 2009 Elsevier Ltd. All rights reserved
Precision measurement of spin-dependent interaction strengths for spin-1 and spin-2 87Rb atoms
We report on precision measurements of spin-dependent interaction-strengths
in the 87Rb spin-1 and spin-2 hyperfine ground states. Our method is based on
the recent observation of coherence in the collisionally driven spin-dynamics
of ultracold atom pairs trapped in optical lattices. Analysis of the Rabi-type
oscillations between two spin states of an atom pair allows a direct
determination of the coupling parameters in the interaction hamiltonian. We
deduce differences in scattering lengths from our data that can directly be
compared to theoretical predictions in order to test interatomic potentials.
Our measurements agree with the predictions within 20%. The knowledge of these
coupling parameters allows one to determine the nature of the magnetic ground
state. Our data imply a ferromagnetic ground state for 87Rb in the f=1
manifold, in agreement with earlier experiments performed without the optical
lattice. For 87Rb in the f=2 manifold the data points towards an
antiferromagnetic ground state, however our error bars do not exclude a
possible cyclic phase.Comment: 11 pages, 5 figure
Adiabatic population transfer via multiple intermediate states
This paper discusses a generalization of stimulated Raman adiabatic passage
(STIRAP) in which the single intermediate state is replaced by intermediate
states. Each of these states is connected to the initial state \state{i} with
a coupling proportional to the pump pulse and to the final state \state{f}
with a coupling proportional to the Stokes pulse, thus forming a parallel
multi- system. It is shown that the dark (trapped) state exists only
when the ratio between each pump coupling and the respective Stokes coupling is
the same for all intermediate states. We derive the conditions for existence of
a more general adiabatic-transfer state which includes transient contributions
from the intermediate states but still transfers the population from state
\state{i} to state \state{f} in the adiabatic limit. We present various
numerical examples for success and failure of multi- STIRAP which
illustrate the analytic predictions. Our results suggest that in the general
case of arbitrary couplings, it is most appropriate to tune the pump and Stokes
lasers either just below or just above all intermediate states.Comment: 14 pages, two-column revtex style, 10 figure
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Very High Temperature Reactor (VHTR) Survey of Materials Research and Development Needs to Support Early Deployment
The VHTR reference concept is a helium-cooled, graphite moderated, thermal neutron spectrum reactor with an outlet temperature of 1000 C or higher. It is expected that the VHTR will be purchased in the future as either an electricity producing plant with a direct cycle gas turbine or a hydrogen producing (or other process heat application) plant. The process heat version of the VHTR will require that an intermediate heat exchanger (IHX) and primary gas circulator be located in an adjoining power conversion vessel. A third VHTR mission - actinide burning - can be accomplished with either the hydrogen-production or gas turbine designs. The first ''demonstration'' VHTR will produce both electricity and hydrogen using the IHX to transfer the heat to either a hydrogen production plant or the gas turbine. The plant size, reactor thermal power, and core configuration will be designed to assure passive decay heat removal without fuel damage during accidents. The fuel cycle will be a once-through very high burnup low-enriched uranium fuel cycle. The purpose of this report is to identify the materials research and development needs for the VHTR. To do this, we focused on the plant design described in Section 2, which is similar to the GT-MHR plant design (850 C core outlet temperature). For system or component designs that present significant material challenges (or far greater expense) there may be some viable design alternatives or options that can reduce development needs or allow use of available (cheaper) materials. Nevertheless, we were not able to assess those alternatives in the time allotted for this report and, to move forward with this material research and development assessment, the authors of this report felt that it was necessary to use a GT-MHR type design as the baseline design
Methods for Assessing Child and Family Outcomes in Early Childhood Special Education Programs
Although many concerns have been raised about methods of assessing outcomes in early childhood special education programs, professionals in the field are nevertheless faced with the need to select appropriate instruments for evaluating child and family outcomes as the result of intervention. A conference to address the current assessment needs of professionals was convened. This paper summarizes this conference, in which five prominent individuals in the field of early childhood special education gave specific recommendations for one child and one family outcome measure which would be applicable to a range of handicapped children between birth and age 5 being served in typical early intervention programs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68510/2/10.1177_027112148600600202.pd
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Entry State Distributions of Discrete Yrast Transitions in Heavy Ion Induced Fusion Reactions
Gamma rays emitted during yrast transitions from compound nuclei are detected with a 4..pi.. multielement gamma ray detector system. Both total pulse height (H) and coincidence fold data (k) are obtained for each event. Results presented include entry state distribution states, k and H projections for some of these distributions, and k and H as a function of spin of the yrast transition. 5 figs. (DWL
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