Search results for "Clusters"
showing 10 items of 1274 documents
Nonlocal field correlations and dynamical Casimir-Polder forces between one excited- and two ground-state atoms
2006
The problem of nonlocality in the dynamical three-body Casimir-Polder interaction between an initially excited and two ground-state atoms is considered. It is shown that the nonlocal spatial correlations of the field emitted by the excited atom during the initial part of its spontaneous decay may become manifest in the three-body interaction. The observability of this new phenomenon is discussed.
Observation of the Continuous Stern-Gerlach Effect on an Electron Bound in an Atomic Ion
1999
We report on the first observation of the continuous Stern-Gerlach effect on an electron bound in an atomic ion. The measurement was performed on a single hydrogenlike ion ( 12C5+) in a Penning trap. The measured g factor of the bound electron, g = 2.001 042(2), is in excellent agreement with the theoretical value, confirming the relativistic correction at a level of 0.1%. This proves the possibility of g-factor determinations on atomic ions to high precision by using the continuous Stern-Gerlach effect. The result demonstrates the feasibility of conducting experiments on single heavy highly charged ions to test quantum electrodynamics in the strong electric field of the nucleus.
The fate of the resonating valence bond in graphene
2011
We apply a variational wave function capable of describing qualitatively and quantitatively the so called "resonating valence bond" in realistic materials, by improving standard ab initio calculations by means of quantum Monte Carlo methods. In this framework we clearly identify the Kekul\'e and Dewar contributions to the chemical bond of the benzene molecule, and we establish the corresponding resonating valence bond energy of these well known structures ($\simeq 0.01$eV/atom). We apply this method to unveil the nature of the chemical bond in undoped graphene and show that this picture remains only within a small "resonance length" of few atomic units.
Teleportation of atomic states via position measurements
2007
We present a scheme for conditionally teleporting an unknown atomic state in cavity QED, which requires two atoms and one cavity mode. The translational degrees of freedom of the atoms are taken into account using the optical Stern-Gerlach model. We show that successful teleportation with probability 1/2 can be achieved through local measurements of the cavity photon number and atomic positions. Neither direct projection onto highly entangled states nor holonomous interaction-time constraints are required.
Spin-lattice relaxation of individual solid-state spins
2018
Understanding the effect of vibrations on the relaxation process of individual spins is crucial for implementing nanosystems for quantum information and quantum metrology applications. In this work, we present a theoretical microscopic model to describe the spin-lattice relaxation of individual electronic spins associated to negatively charged nitrogen-vacancy centers in diamond, although our results can be extended to other spin-boson systems. Starting from a general spin-lattice interaction Hamiltonian, we provide a detailed description and solution of the quantum master equation of an electronic spin-one system coupled to a phononic bath in thermal equilibrium. Special attention is given…
Collisional and thermal ionization of sodium Rydberg atoms III. Experiment and theory fornS andnD states withn= 8–20 in crossed atomic beams
2005
The results of experimental and theoretical studies of collisional ionization of Na Rydberg atoms in nS and nD(n = 8–20) states are presented. Molecular and atomic ions from associative ionization and photoionization by blackbody radiation were detected after pulsed laser excitation of Rydberg states in crossed Na atomic beams. An original method of determination of associative ionization rate constants based on the measurement of ratios of molecular and atomic ion signals was used, which did not require the determination of absolute number density of Rydberg atoms. The measured rate constants of associative ionization of Rydberg atoms in collisions with ground-state Na atoms are compared w…
Direct Bound on the Total Decay Width of the Top Quark inpp¯Collisions ats=1.96 TeV
2009
We present the first direct experimental bound on the total decay width of the top quark, Gamma(t), using 955 pb(-1) of the Tevatron's p (p) over bar collisions recorded by the Collider Detector at Fermilab. We identify 253 top-antitop pair candidate events. The distribution of reconstructed top quark mass from these events is fitted to templates representing different values of the top quark width. Using a confidence interval based on likelihood-ratio ordering, we extract an upper limit at 95% C.L. of Gamma(t) < 13.1 GeV for an assumed top quark mass of 175 GeV/c(2).
Theoretical overview on top pair production and single top production
2012
In this talk I will give an overview on theoretical aspects of top quark physics. The focus lies on top pair production and single top production.
Top-quark pair production cross-section measurements with the ATLAS detector
2019
Measurements of the inclusive and differential top-quark pair production cross sections in proton-proton collisions with the ATLAS detector at the Large Hadron Collider at center-of-mass energies of 8 TeV and 13 TeV are presented. The inclusive measurements reach high precision and are compared to the best available theoretical calculations. Differential measurements of the kinematic properties of the top-quark production are also discussed. These measurements, including results using boosted tops, probe our understanding of top-quark pair production in the TeV regime.
Measurement of Top Quark Polarization in Top-Antitop Events from Proton-Proton Collisions ats=7 TeVUsing the ATLAS Detector
2013
This Letter presents measurements of the polarization of the top quark in top-antitop quark pair events, using 4: 7 fb(-1) of proton-proton collision data recorded with the ATLAS detector at the La ...