6,861 research outputs found

    CPT and QM tests using kaon interferometry

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    The neutral kaon system offers a unique possibility to perform fundamental tests of CPT invariance, as well as of the basic principles of quantum mechanics. The most recent and significant limits on CPT violation are reviewed, including the ones related to possible decoherence mechanisms or Lorentz symmetry breaking, which might be induced by quantum gravity. The experimental results show no deviations from the expectations of quantum mechanics and CPT symmetry, while the accuracy in some cases reaches the interesting Planck scale region. Finally, prospects for this kind of experimental studies at the upgraded DAFNE e+e- collider at Frascati are briefly discussed.Comment: talk at Heavy Quarks and Leptons, Melbourne, 200

    Testing cpt symmetry with neutral k mesons: A review

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    The neutral kaon system is a very peculiar system that offers unique possibilities to perform precise tests of the CPT symmetry. The entanglement of neutral kaon pairs that are produced at a φ-factory opens up new ways and scenarios in order to test this fundamental discrete symmetry. In this paper, the results of the most recent and significant CPT tests are reviewed. Experiments have set stringent limits on the CPT-violating parameters of different phenomenological models, some of them associated to possible decoherence mechanisms or Lorentz symmetry violation which might be justified in a quantum gravity framework. The present results show no violation of CPT symmetry, while their accuracy in some cases reaches the interesting level at which–in the most optimistic scenarios–quantum gravity effects might show up

    Are collapse models testable with quantum oscillating systems? The case of neutrinos, kaons, chiral molecules

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    Collapse models provide a theoretical framework for understanding how classical world emerges from quantum mechanics. Their dynamics preserves (practically) quantum linearity for microscopic systems, while it becomes strongly nonlinear when moving towards macroscopic scale. The conventional approach to test collapse models is to create spatial superpositions of mesoscopic systems and then examine the loss of interference, while environmental noises are engineered carefully. Here we investigate a different approach: We study systems that naturally oscillate --creating quantum superpositions-- and thus represent a natural case-study for testing quantum linearity: neutrinos, neutral mesons, and chiral molecules. We will show how spontaneous collapses affect their oscillatory behavior, and will compare them with environmental decoherence effects. We will show that, contrary to what previously predicted, collapse models cannot be tested with neutrinos. The effect is stronger for neutral mesons, but still beyond experimental reach. Instead, chiral molecules can offer promising candidates for testing collapse models.Comment: accepted by NATURE Scientific Reports, 12 pages, 1 figures, 2 table

    Direct test of time-reversal symmetry in the entangled neutral kaon system at a ϕ\phi-factory

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    We present a novel method to perform a direct T (time reversal) symmetry test in the neutral kaon system, independent of any CP and/or CPT symmetry tests. This is based on the comparison of suitable transition probabilities, where the required interchange of in out states for a given process is obtained exploiting the Einstein-Podolsky-Rosen correlations of neutral kaon pairs produced at a ϕ\phi-factory. In the time distribution between the two decays, we compare a reference transition like the one defined by the time ordered decays (ℓ−,ππ)(\ell^-,\pi\pi) with the T -conjugated one defined by (3π0,ℓ+)(3\pi^0, \ell^+). With the use of this and other T conjugated comparisons, the KLOE-2 experiment at DAΦ\PhiNE could make a significant test

    Theoretical analysis of aliasing noises in cold atom Mach-Zehnder interferometers

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    We present a theoretical analysis of aliasing noises that might appear in cold atom Mach-Zehnder interferometers used for the measurement of various physical quantities. We focus more specifically on single cold atom gyroscopes. To evaluate the level of aliasing noises, we have developed a model based on the power spectral densities of the different identified noise sources as input parameters and which makes use of a servo-loop to realize a precise measurement of the rotation rate. The model allows one to take into account different modes of operation, like a continuous as well as a pulsed or even a multi-ball operation. For monokinetic atoms, we show that the intermodulation noise can be completely filtered out with a continuous mode of operation and an optimum modulation scheme for any modulation frequency but also with a pulsed operation however only for specific launching frequencies. In the case of a real continuous atomic beam having a velocity distribution, it comes out that a high attenuation can be reached which indicates clearly the potential stability improvement that can be expected from a continuous operatio

    Aplicación de elementos finitos en la predicción del factor de intensidad de esfuerzos para fisuras en modo abertura

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    Se expone la importancia del criterio KIC en Fractomecánica y su campo de aplicabilidad. Se indican Las Limitaciones de la formulación analítica. Se proponen dos criterios de evaluación de K1 en base al Método de Elementos Finitos: el Criterio del Promedio de Valores y el Criterio del Intercepto. Se entregan resultados para ambos criterios aplicados a tres especímenes finitos, incluyendo una evaluación de cada criterio

    A large sample study of spin relaxation and magnetometric sensitivity of paraffin-coated Cs vapor cells

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    We have manufactured more than 250 nominally identical paraffin-coated Cs vapor cells (30 mm diameter bulbs) for multi-channel atomic magnetometer applications. We describe our dedicated cell characterization apparatus. For each cell we have determined the intrinsic longitudinal, \sGamma{01}, and transverse, \sGamma{02}, relaxation rates. Our best cell shows \sGamma{01}/2\pi\approx 0.5 Hz, and \sGamma{02}/2\pi\approx 2 Hz. We find a strong correlation of both relaxation rates which we explain in terms of reservoir and spin exchange relaxation. For each cell we have determined the optimal combination of rf and laser powers which yield the highest sensitivity to magnetic field changes. Out of all produced cells, 90% are found to have magnetometric sensitivities in the range of 9 to 30 fTHz. Noise analysis shows that the magnetometers operated with such cells have a sensitivity close to the fundamental photon shot noise limit
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