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2002

Quantum Physics

Articles 1 - 13 of 13

Full-Text Articles in Physics

Higher-Order Evaluation Of The Critical Temperature For Interacting Homogeneous Dilute Bose Gases, Frederico F. F. De Souza Cruz, Marcus Pinto, Rudnei O. Ramos, Paulo Sena May 2002

Higher-Order Evaluation Of The Critical Temperature For Interacting Homogeneous Dilute Bose Gases, Frederico F. F. De Souza Cruz, Marcus Pinto, Rudnei O. Ramos, Paulo Sena

Dartmouth Scholarship

We use the nonperturbative linear δ expansion method to evaluate analytically the coefficients c1 and c''2 that appear in the expansion for the transition temperature for a dilute, homogeneous, three-dimensional Bose gas given by Tc=T0(1+c1an1/3+[c′2ln(an1/3)+c''2]a2n2/3+O(a3n)), where T0 is the result for an ideal gas, a is the s-wave scattering length, and n is the number density. In a previous work the same method has been used to evaluate c1 to order δ2 with the result c1=3.06. Here, we push the calculation to the next two orders obtaining c1=2.45 at order δ3 and c1=1.48 at order δ4. Analyzing the topology …

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Experimental Quantum Cloning Of Single Photons, Antia Lamas-Linares, Christoph Simon, John C. Howell, Dik Bouwmeester Mar 2002

Experimental Quantum Cloning Of Single Photons, Antia Lamas-Linares, Christoph Simon, John C. Howell, Dik Bouwmeester

Mathematics, Physics, and Computer Science Faculty Articles and Research

Although perfect copying of unknown quantum systems is forbidden by the laws of quantum mechanics, approximate cloning is possible. A natural way of realizing quantum cloning of photons is by stimulated emission. In this context, the fundamental quantum limit to the quality of the clones is imposed by the unavoidable presence of spontaneous emission. In our experiment, a single input photon stimulates the emission of additional photons from a source on the basis of parametric down-conversion. This leads to the production of quantum clones with near-optimal fidelity. We also demonstrate universality of the copying procedure by showing that the same …

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Electrons, Stern–Gerlach Magnets, And Quantum Mechanical Propagation, Herman Batelaan Mar 2002

Electrons, Stern–Gerlach Magnets, And Quantum Mechanical Propagation, Herman Batelaan

Department of Physics and Astronomy: Faculty Publications

Quantum corrections to Newton’s equations are obtained and used to illustrate that classical dynamics is embedded explicitly in quantum dynamics. Originally, the resultant set of dynamical equations has been used to shed light on quantum chaos. We show that the method can provide insight into the dynamics of free particles and the harmonic oscillator. We then use it to determine whether Stern–Gerlach magnets can be constructed for free electrons.

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Generalized Moonshine And Orbifold Constructions, Michael Tuite, Rossen Ivanov Jan 2002

Generalized Moonshine And Orbifold Constructions, Michael Tuite, Rossen Ivanov

Conference papers

A brief review is given of some of our recent work on Generalised Monstrous Moonshine using abelian orbifoldings of the Moonshine Module.

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Cooling Atoms In An Optical Trap By Selective Parametric Excitation, Nicola Poli, Robert J. Brecha, Giacomo Roati, Giovanni Modugno Jan 2002

Cooling Atoms In An Optical Trap By Selective Parametric Excitation, Nicola Poli, Robert J. Brecha, Giacomo Roati, Giovanni Modugno

Physics Faculty Publications

We demonstrate the possibility of energy-selective removal of cold atoms from a tight optical trap by means of parametric excitation of the trap vibrational modes. Taking advantage of the anharmonicity of the trap potential, we either selectively remove the most energetic trapped atoms or excite those at the bottom of the trap by tuning the parametric modulation frequency. This process, which had been previously identified as a possible source of heating, also appears to be a robust way for forcing evaporative cooling in anharmonic traps.

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Atomic Hydrogen Cleaning Of Inp(100): Electron Yield And Surface Morphology Of Negative Electron Affinity Activated Surfaces, M. A. Hafez, H. E. Elsayed-Ali Jan 2002

Atomic Hydrogen Cleaning Of Inp(100): Electron Yield And Surface Morphology Of Negative Electron Affinity Activated Surfaces, M. A. Hafez, H. E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

Atomic hydrogen cleaning of the InP(100) surface has been investigated using quantitative reflection high-energy electron diffraction. The quantum efficiency of the surface when activated to negative electron affinity was correlated with surface morphology. The electron diffraction patterns showed that hydrogen cleaning is effective in removing surface contaminants, leaving a clean, ordered, and (2×4)-reconstructed surface. After activation to negative electron affinity, a quantum efficiency of ∼6% was produced in response to photoactivation at 632 nm. Secondary electron emission from the hydrogen-cleaned InP(100)-(2×4) surface was measured and correlated to the quantum efficiency. The morphology of the vicinal InP(100) surface was investigated using …

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Publisher's Note: Η Photoproduction On The Proton For Photon Energies From 0.75 To 1.95 Gev [Phys. Rev. Lett. 89, 222002 (2002)], M. Bektasoglu, K. V. Dharmawardane, G. E. Dodge, C. E. Hyde-Wright, A. Klein, S. E. Kuhn, R. A. Niyazov, S. Stepanyan, L. B. Weinstein, Et Al., Clas Collaboration Jan 2002

Publisher's Note: Η Photoproduction On The Proton For Photon Energies From 0.75 To 1.95 Gev [Phys. Rev. Lett. 89, 222002 (2002)], M. Bektasoglu, K. V. Dharmawardane, G. E. Dodge, C. E. Hyde-Wright, A. Klein, S. E. Kuhn, R. A. Niyazov, S. Stepanyan, L. B. Weinstein, Et Al., Clas Collaboration

Physics Faculty Publications

No abstract provided.

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Η Photoproduction On The Proton For Photon Energies From 0.75 To 1.95 Gev, M. Bektasoglu, K. V. Dharmawardane, G. E. Dodge, C. E. Hyde-Wright, A. Klein, S. E. Kuhn, S. Stepanyan, J. Yun, Et Al., Clas Collaboration Jan 2002

Η Photoproduction On The Proton For Photon Energies From 0.75 To 1.95 Gev, M. Bektasoglu, K. V. Dharmawardane, G. E. Dodge, C. E. Hyde-Wright, A. Klein, S. E. Kuhn, S. Stepanyan, J. Yun, Et Al., Clas Collaboration

Physics Faculty Publications

Differential cross sections for γp→ηp have been measured with tagged real photons for incident photon energies from 0.75 to 1.95 GeV. Mesons were identified by missing mass reconstruction using kinematical information for protons scattered in the production process. The data provide the first extensive angular distribution measurements for the process above W = 1.75  GeV. Comparison with preliminary results from a constituent quark model support the suggestion that a third S11 resonance with mass ∼1.8  GeV couples to the ηN channel.

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First Measurement Of The Double Spin Asymmetry In →E→P → E ‘Π⁺ In The Resonance Region, G. E. Dodge, K. V. Dharmawardane, T. A. Forest, C. E. Hyde-Wright, A. Klein, S. E. Kuhn, R. A. Niyazov, L. B. Weinstein, J. Yun, Et. Al., Clas Collaboration Jan 2002

First Measurement Of The Double Spin Asymmetry In →E→P → E ‘Π⁺ In The Resonance Region, G. E. Dodge, K. V. Dharmawardane, T. A. Forest, C. E. Hyde-Wright, A. Klein, S. E. Kuhn, R. A. Niyazov, L. B. Weinstein, J. Yun, Et. Al., Clas Collaboration

Physics Faculty Publications

The double spin asymmetry in the →e→p → e' π+n reaction has been measured for the first time in the resonance region for four-momentum transfer Q2 = 0.35-1.5 GeV2. Data were taken at Jefferson Lab with the CLAS detector using a 2.6 GeV polarized electron beam incident on a polarized solid NH3 target. Comparison with predictions of phenomenological models shows strong sensitivity to resonance contributions. Helicity-1/2 transitions are found to be dominant in the second and third resonance regions. The measured asymmetry is consistent with a faster rise with Q2 …

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Some Irrational Generalised Moonshine From Orbifolds, Rossen Ivanov, Michael Tuite Jan 2002

Some Irrational Generalised Moonshine From Orbifolds, Rossen Ivanov, Michael Tuite

Articles

We verify the Generalised Moonshine conjectures for some irrational modular functions for theMonster centralisers related to the Harada-Norton, Held, M12 and L3(3) simple groups based on certain orbifolding constraints. We find explicitly the fixing groups of the hauptmoduls arising in each case.

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Rational Generalized Moonshine From Abelian Orbifoldings Of The Moonshine Module, Rossen Ivanov, Michael Tuite Jan 2002

Rational Generalized Moonshine From Abelian Orbifoldings Of The Moonshine Module, Rossen Ivanov, Michael Tuite

Articles

We consider orbifoldings of the Moonshine Module with respect to the abelian group generated by a pair of commuting Monster group elements with one of prime order p = 2, 3, 5, 7 and the other of order pk for k = 1 or k prime. We show that constraints arising from meromorphic orbifold conformal field theory allow us to demonstrate that each orbifold partition function with rational coefficients is either constant or is a hauptmodul for an explicitly found modular fixing group of genus zero. We thus confirm in the cases considered the Generalised Moonshine conjectures for all rational …

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Phase And Absorption Gratings For Electrons, Hong Gao, Glen Gronniger, Daniel Friemund, Alex Cronin Jan 2002

Phase And Absorption Gratings For Electrons, Hong Gao, Glen Gronniger, Daniel Friemund, Alex Cronin

Department of Physics and Astronomy: Faculty Publications

We report the experimental realization of phase and absorption gratings for electrons. Phase gratings made with standing waves of light with a periodicity of 266 nm are used to diffract 380 eV electrons [1]. Material gratings of 100 and 200 nm periodicity are used to diffract 500 eV electrons. We are exploring the possibility to use these gratings for low energy electron interferometry.

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Optimal Simulation Of Two-Qubit Hamiltonians Using General Local Operations, C. H. Bennett, J. I. Cirac, Matthew S. Leifer, D. W. Leung, N. Linden, S. Popescu, G. Vidal Jan 2002

Optimal Simulation Of Two-Qubit Hamiltonians Using General Local Operations, C. H. Bennett, J. I. Cirac, Matthew S. Leifer, D. W. Leung, N. Linden, S. Popescu, G. Vidal

Mathematics, Physics, and Computer Science Faculty Articles and Research

We consider the simulation of the dynamics of one nonlocal Hamiltonian by another, allowing arbitrary local resources but no entanglement or classical communication. We characterize notions of simulation, and proceed to focus on deterministic simulation involving one copy of the system. More specifically, two otherwise isolated systems A and B interact by a nonlocal Hamiltonian H≠HA+HB . We consider the achievable space of Hamiltonians H8 such that the evolution e2iH8t can be simulated by the interaction H interspersed with local operations. For any dimensions of A and B, and any nonlocal Hamiltonians H and H8, there exists a scale factor …

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