11 research outputs found
Raman spectroscopy of a single ion coupled to a high-finesse cavity
We describe an ion-based cavity-QED system in which the internal dynamics of
an atom is coupled to the modes of an optical cavity by vacuum-stimulated Raman
transitions. We observe Raman spectra for different excitation polarizations
and find quantitative agreement with theoretical simulations. Residual motion
of the ion introduces motional sidebands in the Raman spectrum and leads to ion
delocalization. The system offers prospects for cavity-assisted
resolved-sideband ground-state cooling and coherent manipulation of ions and
photons.Comment: 8 pages, 6 figure
Quantifying decoherence in continuous variable systems
We present a detailed report on the decoherence of quantum states of
continuous variable systems under the action of a quantum optical master
equation resulting from the interaction with general Gaussian uncorrelated
environments. The rate of decoherence is quantified by relating it to the decay
rates of various, complementary measures of the quantum nature of a state, such
as the purity, some nonclassicality indicators in phase space and, for two-mode
states, entanglement measures and total correlations between the modes.
Different sets of physically relevant initial configurations are considered,
including one- and two-mode Gaussian states, number states, and coherent
superpositions. Our analysis shows that, generally, the use of initially
squeezed configurations does not help to preserve the coherence of Gaussian
states, whereas it can be effective in protecting coherent superpositions of
both number states and Gaussian wave packets.Comment: Review article; 36 pages, 19 figures; typos corrected, references
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Hybrid Mechanical Systems
We discuss hybrid systems in which a mechanical oscillator is coupled to
another (microscopic) quantum system, such as trapped atoms or ions,
solid-state spin qubits, or superconducting devices. We summarize and compare
different coupling schemes and describe first experimental implementations.
Hybrid mechanical systems enable new approaches to quantum control of
mechanical objects, precision sensing, and quantum information processing.Comment: To cite this review, please refer to the published book chapter (see
Journal-ref and DOI). This v2 corresponds to the published versio
Decoherence control in microwave cavities
We present a scheme able to protect the quantum states of a cavity mode
against the decohering effects of photon loss. The scheme preserves quantum
states with a definite parity, and improves previous proposals for decoherence
control in cavities. It is implemented by sending single atoms, one by one,
through the cavity. The atomic state gets first correlated to the photon number
parity. The wrong parity results in an atom in the upper state. The atom in
this state is then used to inject a photon in the mode via adiabatic transfer,
correcting the field parity. By solving numerically the exact master equation
of the system, we show that the protection of simple quantum states could be
experimentally demonstrated using presently available experimental apparatus.Comment: 13 pages, RevTeX, 8 figure
Molecular characterization of two sub-family specific monoclonal antibodies to meningococcal Factor H binding protein
Factor H binding protein (FHbp) is a component of two licensed vaccines for prevention of sepsis and meningitis caused by serogroup B meningococci. FHbp binds human Factor H (FH), which contributes to evasion of host immunity and FHbp sequence variants can be classified into two sub-families. Antibodies against FHbp elicit complement-mediated killing and can inhibit recruitment of FH to the bacterial surface. We report epitope mapping studies of two murine IgG mAbs, designated JAR 31 and JAR 36, isolated from a mouse immunized with FHbp in sub-family A, which is present in âŒ30â40% of invasive isolates. In the present study, we tested the reactivity of mAbs JAR 31 and JAR 36 with seven natural FHbp sequence variants from different phylogenic groups. We screened bacteriophage-displayed peptide libraries to identify amino acid residues contributing to the JAR 36 epitope. Based on the reactivities of mAbs JAR 31 and JAR 36 with the seven FHbp variants, and the frequent occurrences of aspartate (D) and lysine (K) residues in the JAR 36-bound phage peptides, we selected six residues in the carboxyl-terminal region of FHbp for replacement with alanine (A). The D201A and K203A substitutions respectively eliminated and decreased binding of mAbs JAR 31 and JAR 36 to FHbp. These substitutions did not affect binding of the control mAb JAR 33 or of human FH. JAR 31 or JAR 36 mediated cooperative complement-mediated bactericidal activity with other anti-FHbp mAbs. The identification of two amino acid residues involved in the epitopes recognized by these anti-FHbp mAbs may contribute to a more complete understanding of the spatial requirements for cooperative anti-FHbp mAb bactericidal activity
Quantitative genome-scale analysis of protein localization in an asymmetric bacterium
Despite the importance of subcellular localization for cellular activities, the lack of high-throughput, high-resolution imaging and quantitation methodologies has limited genomic localization analysis to a small number of archival studies focused on C-terminal fluorescent protein fusions. Here, we develop a high-throughput pipeline for generating, imaging, and quantitating fluorescent protein fusions that we use for the quantitative genomic assessment of the distributions of both N- and C-terminal fluorescent protein fusions. We identify nearly 300 localized Caulobacter crescentus proteins, up to 10-fold more than were previously characterized. The localized proteins tend to be involved in spatially or temporally dynamic processes and proteins that function together and often localize together as well. The distributions of the localized proteins were quantitated by using our recently described projected system of internal coordinates from interpolated contours (PSICIC) image analysis toolkit, leading to the identification of cellular regions that are over- or under-enriched in localized proteins and of potential differences in the mechanisms that target proteins to different subcellular destinations. The Caulobacter localizome data thus represent a resource for studying both global properties of protein localization and specific protein functions, whereas the localization analysis pipeline is a methodological resource that can be readily applied to other systems