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27 results on '"Weidman, P. D."'

1. Coulomb interaction-driven entanglement of electrons on helium

Author

Beysengulov, Niyaz R., Pollanen, Johannes, Schøyen, Øyvind S., Bilek, Stian D., Flaten, Jonas B., Leinonen, Oskar, Kristiansen, Håkon Emil, Stewart, Zachary J., Weidman, Jared D., Wilson, Angela K., and Hjorth-Jensen, Morten

Subjects
Quantum Physics, Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Atomic Physics
Abstract

The generation and evolution of entanglement in quantum many-body systems is an active area of research that spans multiple fields, from quantum information science to the simulation of quantum many-body systems encountered in condensed matter, subatomic physics, and quantum chemistry. Motivated by recent experiments exploring quantum information processing systems with electrons trapped above the surface of cryogenic noble gas substrates, we theoretically investigate the generation of \emph{motional} entanglement between two electrons via their unscreened Coulomb interaction. The model system consists of two electrons confined in separate electrostatic traps which establish microwave frequency quantized states of their motion. We compute the motional energy spectra of the electrons, as well as their entanglement, by diagonalizing the model Hamiltonian with respect to a single-particle Hartree product basis. This computational procedure can in turn be employed for device design and guidance of experimental implementations. In particular, the theoretical tools developed here can be used for fine tuning and optimization of control parameters in future experiments with electrons trapped above the surface of superfluid helium or solid neon., Comment: Revised figures and discussions

Published
2023

17. Prototypical Transition-Metal Carbenes, (CO)5Cr═CH2, (CO)4Fe═CH2, (CO)3Ni═CH2, (CO)5Mo═CH2, (CO)4Ru═CH2, (CO)3Pd═CH2, (CO)5W═CH2, (CO)4Os═CH2, and (CO)3Pt═CH2: Challenge to Experiment

Author

Weidman, Jared D., Estep, Marissa L., and Schaefer, Henry F.

Abstract

Transition-metal carbenes are useful in organometallic chemistry due to their demonstrated use as catalysts in carbon–carbon bond-forming reactions. Yet the prototypical transition-metal carbenes, consisting of a single metal center doubly bonded to a methylene ligand and surrounded by carbonyls, have been elusive to experimental synthesis. This theoretical work examines the structures and properties of nine prototypical transition-metal carbenes. Optimized values for M═CH2bond lengths, dissociation energies, and vibrational frequencies are reported. The M═CH2bond distances range from 1.81 (Ni) to 2.05 Å (Pd). The M═CH2dissociation energies fall in the range of 16.4 (Pd) to 92.3 kcal mol–1(Os). The spectroscopic observation of several of these molecules should be possible.

Published
2018
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18. On the Instability of Spheres Settling through a Vertical Pipe Filled with HPG.

Author

Weidman, P. D., Roberts, B., and Eisen, S.

Subjects
OSCILLATIONS, AERODYNAMICS, SPHERES, HELICAL waveguides, TUBES, WATER, FLUIDS, EXPERIMENTS
Abstract

An extensive set of experiments were performed to determine the stability boundary for the longitudinal oscillation of steel spheres settling through Hydroxy Propyl Guar (HPG) contained in long vertical tubes, a phenomenon first reported by Mollinger, et al. (1999). Results are reported in d/D-pH parameter space, where d is the sphere diameter and D is the internal diameter of a tube. Longitudinal oscillations, which owe their existence to the self-healing nature of the gel, occur over the region 0.48 < d/D < 0.86 and 8.31 < pH < 8.82. We discover that the upper pH limit of this stability domain is linked to the HPG gel point. During the course of experimentation, additional instabilities in the form of high-frequency transverse oscillations or helical motions were discovered and documented. The pure transverse oscillations found in the domain 8.035 < pH < 8.31 and 0.9 < d/D < 0.6 result from the elastic nature of the guar in this region. For 6.25 < pH < 8.035 transverse oscillations or stable descents are interspersed between bands of tight helical motion at large d/D and wide helical motion at low d/D. At the lowest value pH = 6.25 the guar is a Newtonian fluid, yet the spiral motion persists in small bands of d/D. We have verified, in the literature and through additional experiments using distilled water as the Newtonian liquid that the spiral motion of spheres falling inside vertical tubes does indeed exist. [ABSTRACT FROM AUTHOR]

Published
2012
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25. Wake transition and blockage effects on cylinder base pressures

Author

Weidman, Patrick D. and Weidman, Patrick D.

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. Base pressure measurements of circular cylinders at Reynolds numbers from 100 to 3 x [...] were obtained in a low speed wind tunnel. Pressure distributions from [...] to [...] were also obtained. In the Reynolds number region from the first appearance of an unsteady wake to the critical Reynolds number the base pressure coefficient shows two maximums and two minimums. The first maximum (Rd [...] 50) coincides with the first appearance, of the Karman vortex street. The succeeding minimum (Rd [...] 300) probably corresponds to the movement of the onset of transition from the end of the vortex-formation region into the free shear layers. The following maximum (Rd [...] 2200) is accompanied by a small discontinuity in the base pressure curve and a decrease in the Strouhal number. The final minimum corresponds to the end of the Schiller-Linke region, at which point transition to turbulence occurs in the free shear layers very near to the shoulder of the cylinder. A comparison of the blockage correction theories of Maskell and Allen and Vincenti was made at [...] = 6 x [...]. The value of the base pressure coefficient in an unlimited stream at this Reynolds number was found to be [...] = -1.215 for cylinders of one particular roughness, though this value depends on other unit Reynolds number effects. These effects can also result in a significant Reynolds number shift of the base pressure coefficients.

Published
1968

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