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Atom Interferometers: Beyond Complementarity Principles  [PDF]
Zhi-Yuan Li
Physics , 2001,
Abstract: Complementarity lies at the heart of conceptual foundation of orthodox quantum mechanics. The wave-particle duality makes it impossible to tell which slit each particle passes through and still observe an interference pattern in a Young's double-slit experiment. In this paper, this duality is appraised under the standard formulation of quantum mechanics for atom interferometers. It is found that the internal freedoms like electronic states of an atom can be used to detect the which-path information of each atom while uphold the interference pattern of atoms when the center-of-mass motion of atoms is detected.
Atom-Wall interaction  [PDF]
Daniel Bloch,Martial Ducloy
Physics , 2005,
Abstract: This chapter deals with atom-wall interaction occurring in the "long-range" regime (typical distances: 1-1000 nm), when the electromagnetic fluctuations of an isolated atom are modified by the vicinity with a surface. Various regimes of interaction are discussed in an Introductory part, from Cavity Quantum ElectroDynamics modifications of the spontaneous emission, to Casimir effect, with emphasis on the atom-surface van der Waals interaction, characterized as a near-field interaction governed by a z-3 dependence. The major part of the Chapter focuses on the experimental measurements of this van der Waals interaction, reviewing various recent techniques, and insists upon optical techniques, and notably selective reflection spectroscopy which is particularly well-suited when excited atoms are considered. A review of various experiments illustrates the specific effects associated with a resonant coupling between the atomic excitation and surface modes, from van der Waals repulsion to surface-induced resonant transfer, and with anisotropy effects, including metastability transfer induced by a quadrupole contribution in the interaction. The effects of a thermal excitation of the surface -with a possible remote energy transfer to an atom-, and of interaction with nanobodies -which are intrinsically non planar- are notably discussed among the prospects.
Correlations in local measurements on a quantum state, and complementarity as an explanation of nonclassicality  [PDF]
Shengjun Wu,Uffe V. Poulsen,Klaus M?lmer
Physics , 2009, DOI: 10.1103/PhysRevA.80.032319
Abstract: We consider the classical correlations that two observers can extract by measurements on a bipartite quantum state, and we discuss how they are related to the quantum mutual information of the state. We show with several examples how complementarity gives rise to a gap between the quantum and the classical correlations, and we relate our quantitative finding to the so-called classical correlation locked in a quantum state. We derive upper bounds for the sum of classical correlation obtained by measurements in different mutually unbiased bases and we show that the complementarity gap is also present in the deterministic quantum computation with one quantum bit.
Elementary Atom Interaction with Matter  [PDF]
Stanislaw Mrowczynski
Physics , 1998,
Abstract: The calculations of the elementary atom (the Coulomb bound state of elementary particles) interaction with the atom of matter, which are performed in the Born approximation, are reviewed. We first discuss the nonrelativistic approach and then its relativistic generalization. The cross section of the elementary atom excitation and ionization as well as the total cross section are considered. A specific selection rule, which applies for the atom formed as positronium by particle-antiparticle pair, is analyzed.
Complementarity of Weak Lensing and Peculiar Velocity Measurements in Testing General Relativity  [PDF]
Yong-Seon Song,Gong-Bo Zhao,David Bacon,Kazuya Koyama,Robert C Nichol,Levon Pogosian
Physics , 2010, DOI: 10.1103/PhysRevD.84.083523
Abstract: We explore the complementarity of weak lensing and galaxy peculiar velocity measurements to better constrain modifications to General Relativity. We find no evidence for deviations from GR on cosmological scales from a combination of peculiar velocity measurements (for Luminous Red Galaxies in the Sloan Digital Sky Survey) with weak lensing measurements (from the CFHT Legacy Survey). We provide a Fisher error forecast for a Euclid-like space-based survey including both lensing and peculiar velocity measurements, and show that the expected constraints on modified gravity will be at least an order of magnitude better than with present data, i.e. we will obtain 5% errors on the modified gravity parametrization described here. We also present a model--independent method for constraining modified gravity parameters using tomographic peculiar velocity information, and apply this methodology to the present dataset.
Interaction-Free Measurements  [PDF]
Lev Vaidman
Physics , 1996,
Abstract: A brief review of interaction-free measurements (IFM) is presented. The IFM is a solution of a quantum puzzle: How to test a bomb which explodes on every test without exploding it? This paper was given in the Oxford conference in honor of Roger Penrose.
Weak localisation, interaction effects and the metallic phase in p-SiGe  [PDF]
P. T. Coleridge,A. S. Sachrajda,P. Zawadzki
Physics , 1999,
Abstract: Magnetoresistance results are presented for p-SiGe samples on the metallic side of the B=0 metal-insulator transition. It was possible to separate the weak localisation and Zeeman interaction effects but the results could not be explained quantitatively within the framework of standard theories for quantum corrections of a weakly interacting 2-dimensional system. Analysis using a theory for interaction corrections at intermediate temperatures, recently proposed by Zala, Narozhny and Aleiner, provided values of the Fermi liquid parameter $F_0^{\sigma}$ of order -0.5. Similar values also explain the linear increase of resistance with temperature characteristic of the metallic phase. e
Are Interaction-free Measurements Interaction Free?  [PDF]
L. Vaidman
Physics , 2000, DOI: 10.1134/1.1405211
Abstract: In 1993 Elitzur and Vaidman introduced the concept of interaction-free measurements which allowed finding objects without ``touching'' them. In the proposed method, since the objects were not touched even by photons, thus, the interaction-free measurements can be called as ``seeing in the dark''. Since then several experiments have been successfully performed and various modifications were suggested. Recently, however, the validity of the term ``interaction-free'' has been questioned. The criticism of the name is briefly reviewed and the meaning of the interaction-free measurements is clarified.
The impact of magnetic properties on atom-wall interaction  [PDF]
G. Bimonte,G. L. Klimchitskaya,V. M. Mostepanenko
Physics , 2009, DOI: 10.1103/PhysRevA.79.042906
Abstract: The Lifshitz-type formulas for the free energy and Casimir-Polder force acting between an atom possessing a permanent magnetic moment and a wall made of different materials are derived. Simple model allowing analytic results is considered where the atomic magnetic susceptibility is frequency-independent and wall is made of ideal metal. Numerical computations of the Casimir-Polder force are performed for H atom interacting with walls made of ideal metal, nonmagnetic (Au) and ferromagnetic (Fe) metals and of ferromagnetic dielectric. It is shown that for the first three wall materials the inclusion of the magnetic moment of an atom decreases and for the fourth material increases the magnitude of the Casimir-Polder force.
Sparsity without the Complexity: Loss Localisation using Tree Measurements  [PDF]
Vijay Arya,Darryl Veitch
Computer Science , 2011,
Abstract: We study network loss tomography based on observing average loss rates over a set of paths forming a tree -- a severely underdetermined linear problem for the unknown link loss probabilities. We examine in detail the role of sparsity as a regularising principle, pointing out that the problem is technically distinct from others in the compressed sensing literature. While sparsity has been applied in the context of tomography, key questions regarding uniqueness and recovery remain unanswered. Our work exploits the tree structure of path measurements to derive sufficient conditions for sparse solutions to be unique and the condition that $\ell_1$ minimization recovers the true underlying solution. We present a fast single-pass linear algorithm for $\ell_1$ minimization and prove that a minimum $\ell_1$ solution is both unique and sparsest for tree topologies. By considering the placement of lossy links within trees, we show that sparse solutions remain unique more often than is commonly supposed. We prove similar results for a noisy version of the problem.
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