495 research outputs found
Continuous Generation of Quantum Light from a Single Ground-State Atom in an Optical Cavity
We show an optical wave-mixing scheme that generates quantum light by means
of a single three-level atom. The atom couples to an optical cavity and two
laser fields that together drive a cycling current within the atom. Weak
driving in combination with strong atom-cavity coupling induces transitions
between the dark states of the system, accompanied by single-photon emission
and suppression of atomic excitation by quantum interference. For strong
driving, the system can generate coherent or Schr\"odinger cat-like fields with
frequencies distinct from those of the applied lasers.Comment: 5 pages, 4 figure
Biologia da mosca-branca (Bemisia argentifolii) em tomate e repolho.
bitstream/item/103104/1/pa-1.pd
Bilinear and quadratic Hamiltonians in two-mode cavity quantum electrodynamics
In this work we show how to engineer bilinear and quadratic Hamiltonians in
cavity quantum electrodynamics (QED) through the interaction of a single driven
two-level atom with cavity modes. The validity of the engineered Hamiltonians
is numerically analyzed even considering the effects of both dissipative
mechanisms, the cavity field and the atom. The present scheme can be used, in
both optical and microwave regimes, for quantum state preparation, the
implementation of quantum logical operations, and fundamental tests of quantum
theory.Comment: 11 pages, 3 figure
Metabolic fingerprinting of <i>Lactobacillus paracasei</i>:the optimal quenching strategy
BACKGROUND: Quenching in cold buffered methanol at −40 °C has long been the preferred method for sub-second inactivation of cell metabolism during metabolic fingerprinting. However, methanol is known to cause intracellular metabolite leakage of microbial cells, making the distinction between intra- and extracellular metabolites in microbial systems challenging. In this paper, we tested three quenching protocols proposed for microbial cultures: fast filtration, cold buffered methanol and cold glycerol saline. RESULTS: Our results clearly showed that cold glycerol saline quenching resulted in the best recovery of intracellular metabolites in Lactobacillus paracasei subsp. paracasei (L. paracasei). Membrane integrity assayed by propidium iodide revealed that approximately 10 % of the L. paracasei cell membranes were damaged by contact with the cold buffered methanol solution, whilst cold glycerol saline quenching led to minimal cell damage. Due to the nature of the L. paracasei culture, fast filtration took several minutes, which is far from ideal for metabolites with high intracellular turnover rates. CONCLUSION: The implementation of a reliable, reproducible quenching method is essential within the metabolomics community. Cold glycerol saline prevented leakage of intracellular metabolites, and, thus, allowed more accurate determinations of intracellular metabolite levels
Nonadiabatic coherent evolution of two-level systems under spontaneous decay
In this paper we extend current perspectives in engineering reservoirs by
producing a time-dependent master equation leading to a nonstationary
superposition equilibrium state that can be nonadiabatically controlled by the
system-reservoir parameters. Working with an ion trapped inside a nonindeal
cavity we first engineer effective Hamiltonians that couple the electronic
states of the ion with the cavity mode. Subsequently, two classes of
decoherence-free evolution of the superposition of the ground and decaying
excited levels are achieved: those with time-dependent azimuthal or polar
angle. As an application, we generalise the purpose of an earlier study [Phys.
Rev. Lett. 96, 150403 (2006)], showing how to observe the geometric phases
acquired by the protected nonstationary states even under a nonadiabatic
evolution.Comment: 5 pages, no figure
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