120745638
SHORT-RANGE CORRELATIONS AND ELASTIC ELECTRON SCATTERING.
19234257
Experimental realization of decoherence-free subspace in neutron interferometry.
A decoherence-free subspace (DFS) is an important class of quantum-error-correcting (QEC) codes that have been proposed for fault-tolerant quantum computation. The applications of QEC techniques, however, are not limited to quantum-information processing (QIP). Here we demonstrate how QEC codes may be used to improve experimental designs of quantum devices to achieve noise suppression. In particular, neutron interferometry is used as a test bed to show the potential for adding quantum error correction to quantum measurements. We built a five-blade neutron interferometer that incorporates both a standard Mach-Zender configuration and a configuration based on a DFS. Experiments verify that the DFS interferometer is protected against low-frequency mechanical vibrations. We anticipate these improvements will increase the range of applications for matter-wave interferometry.
120225283
Quark structure of simple and complex hadrons
Abstract A realistic description of the meson and baryon spectra can be achieved within a non-relativistic quark model but the coupling of baryonic q 3 -states to meson-baryon decay channels is of vital importance for a proper description of the decay properties of baryon resonances which are interpreted as bound (q 3 )-configurations embedded in meson continua. This dressing of q 3 -states automatically leads to an energy- and state dependent baryon-baryon interaction that allows a formulation of a multibaryon Hamiltonian for complex hadrons. Within this framework the subnuclear dynamics of intermediate energy excitations of complex hadrons is discussed.
120855950
Pionic and electromagnetic excitation of A* resonances
The nuclear excitation spectrum in the Delta (3,3) energy range is studied by comparing elastic pion scattering with coherent neutral pion photoproduction. The corresponding multipole excitation strength distributions are found to be quite different. This emphasises the role of the electromagnetic excitations of nuclei for the investigation of the A* resonances which is complementary to their mesonic excitation. Results are presented for 12C( gamma , pi 0) 12C(GS); they are compared with those of the phenomenological isobar doorway model and of DWIA calculations.
13703277
COLLECTIVE TREATMENT OF THE GIANT RESONANCES IN SPHERICAL NUCLEI.
In a collective treatment the energies of the giant resonances are given by the boundary conditions at the nuclear surface, which is subject to vibration in spherical nuclei. The general form of the coupling between these two collective motions is given by angular-momentum and parity conservation. The coupling constants are completely determined within the hydrodynamical model. In the present treatment the influence of the surface vibrations on the total photon-absorption cross section is calculated. It turns out that in most of the spherical nuclei this interaction leads to a pronounced structure in the cross section. The agreement with the experiments in medium-heavy nuclei is striking; many of the experimental characteristics are reproduced by the present calculations. In some nuclei, however, there seem to be indications of single-particle excitations which are not yet contained in this work.
121598524
Collective resonance in pion-nucleus scattering
Pion-nucleus scattering is described by the excitation of bound nucleons into the ..delta.. resonance leading to isobaric resonances of the whole nucleus. A few broad collective resonances of different multipolarity are shown to dominate elastic and inelastic ..pi..-/sup 12/C scattering. From the qualitatively good agreement with the data, we conclude that those giant isobaric resonances are a general feature of the nuclear excitation spectrum in the ..delta.. (3, 3) energy range.
122949791
Deployment of the first CDMS II ZIP Detectors at the Stanford Underground Facility
Abstract The CDMS II experiment deployed the first set of ZIP (Z-dependent Ionization and Phonon) detectors at the Stanford Underground Facility (SUF) shallow depth site in the spring of 2000. With a payload consisting of 3 Ge (250g ea.) and 3 Si (100g ea.) ZIPs, the run was the first demostration of multiple ZIPs operating simltaneously. Good discrimination between electron and nuclear recoil events of 99.8% was established, down to recoil energies of 10 keV. A measurement of the γ, β, and neutron backgrounds was made.
17072730
Exclusion limits on the WIMP-nucleon cross section from the first run of the Cryogenic Dark Matter Search in the Soudan Underground Laboratory
The Cryogenic Dark Matter Search (CDMS-II) employs low-temperature Ge and Si detectors to seek Weakly Interacting Massive Particles (WIMPs) via their elastic scattering interactions with nuclei. Simultaneous measurements of both ionization and phonon energy provide discrimination against interactions of background particles. For recoil energies above 10 keV, events due to background photons are rejected with > 99.99% efficiency. Electromagnetic events very near the detector surface can mimic nuclear recoils because of reduced charge collection, but these surface events are rejected with > 96% efficiency by using additional information from the phonon pulse shape. Efficient use of active and passive shielding, combined with the 2090 m.w.e. overburden at the experimental site in the Soudan mine, makes the background from neutrons negligible for this first exposure. All cuts are determined in a blind manner from in situ calibrations with external radioactive sources without any prior knowledge of the event distribution in the signal region. Resulting efficiencies are known to {approx}10%. A single event with a recoil of 64 keV passes all of the cuts and is consistent with the expected misidentification rate of surface-electron recoils. Under the assumptions for a standard dark matter halo, these data exclude previously unexplored parameter space for both spin-independent and spin-dependent WIMP-nucleon elastic scattering. The resulting limit on the spin-independent WIMP-nucleon elastic-scattering cross-section has a minimum of 4 x 10{sup -43} cm{sup 2} at a WIMP mass of 60 GeV c{sup -2}. The minimum of the limit for the spin-dependent WIMP-neutron elastic-scattering cross-section is 2 x 10{sup -37} cm{sup 2} at a WIMP mass of 50 GeV c{sup -2}.
119277250
Infrared singularities in Landau gauge Yang-Mills theory
We present a more detailed picture of the infrared regime of Landau-gauge Yang-Mills theory. This is done within a novel framework that allows one to take into account the influence of finite scales within an infrared power counting analysis. We find that there are two qualitatively different infrared fixed points of the full system of Dyson-Schwinger equations. The first extends the known scaling solution, where the ghost dynamics is dominant and gluon propagation is strongly suppressed. It features in addition to the strong divergences of gluonic vertex functions in the previously considered uniform scaling limit, when all external momenta tend to zero, also weaker kinematic divergences, when only some of the external momenta vanish. The second solution represents the recently proposed decoupling scenario where the gluons become massive and the ghosts remain bare. In this case we find that none of the vertex functions is enhanced, so that the infrared dynamics is entirely suppressed. Our analysis also provides a strict argument why the Landau-gauge gluon dressing function cannot be infrared divergent.
118486774
Quantum gates and multipartite entanglement resonances realized by motion
We demonstrate the presence of genuine multipartite entanglement between the modes of quantum fields in non-uniformly moving cavities. The transformations generated by the cavity motion can be considered as multipartite quantum gates. We present two setups for which multi-mode entanglement can be generated for bosons and fermions. As a highlight we show that the bosonic genuine multipartite correlations can be resonantly enhanced. Our results provide fundamental insights into the structure of Bogoliubov transformations and suggest strong links between quantum information, quantum fields in curved spacetimes and gravitational analogs by way of the equivalence principle.
89606799
Lorentz invariance of entanglement classes in multipartite systems
We analyze multipartite entanglement in systems of spin-½ particles from a relativistic perspective. General conditions which have to be met for any classification of multipartite entanglement to be Lorentz invariant are derived, which contributes to a physical understanding of entanglement classification. We show that quantum information in a relativistic setting requires the partition of the Hilbert space into particles to be taken seriously. Furthermore, we study exemplary cases and show how the spin and momentum entanglement transforms relativistically in a multipartite setting.