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Articles 1 - 5 of 5
Full-Text Articles in Physics
Critique Of The Wigner Tunneling Speed And A Proposed Alternative, P Krekora, Q Su, Rainer Grobe
Critique Of The Wigner Tunneling Speed And A Proposed Alternative, P Krekora, Q Su, Rainer Grobe
Faculty publications – Physics
In the context of superluminal propagation of wave packets through potential barriers, the tunneling speed is usually characterized by the Wigner velocity. We propose an alternative speed that takes into account the interference between the incoming and the reflected waves and leads to a better estimation of arrival time for a wave packet entering the tunneling region. This arrival time is derived by an extrapolation from inside the barrier. The analytical theory is based on the stationary phase approximation whose validity is justified by a comparison with the numerical solution of the time-dependent Dirac equation.
The Vacuum Excitation And Squeezing Properties Of Two Quantum Oscillators With Delta-Kicked Interactions, J Y. Ji, David Peak
The Vacuum Excitation And Squeezing Properties Of Two Quantum Oscillators With Delta-Kicked Interactions, J Y. Ji, David Peak
All Physics Faculty Publications
The vacuum excitation and squeezing of two harmonic oscillators with delta-kicked interactions for four types of elementary coupling are studied. The exact quantum motion for the Heisenberg operators and the explicit form of squeezing operators are found. The variances are calculated to study the squeezing properties for position, momentum and generalized quadrature operators.
Effects Of Relativity On The Time-Resolved Tunneling Of Electron Wave Packets, P Krekora, Q Su, Rainer Grobe
Effects Of Relativity On The Time-Resolved Tunneling Of Electron Wave Packets, P Krekora, Q Su, Rainer Grobe
Faculty publications – Physics
We solve numerically the time-dependent Dirac equation for a quantum wave packet tunneling through a potential barrier. We analyze the spatial probability distribution of the transmitted wave packet in the context of the possibility of effectively superluminal peak and front velocities of the electron during tunneling. Both the Dirac and Schrodinger theories predict superluminal tunneling speeds. However, in contrast to the Dirac theory the Schrodinger equation allows a possible violation of causality. Based on an analysis of the tunneling process in full temporal and spatial resolution, we introduce an instantaneous tunneling speed that can be computed inside the potential barrier.
Numerical Study Of Optical Delay In Semiconductor Multilayer Distributed Bragg Reflector And Tunable Microcavity Structures, Michael I. K. Etan
Numerical Study Of Optical Delay In Semiconductor Multilayer Distributed Bragg Reflector And Tunable Microcavity Structures, Michael I. K. Etan
Theses and Dissertations
The Air Force has a growing need for the greater bandwidth, speed, and flexibility offered by optical communication links. Future space systems and airborne platforms will most likely use optical signals for efficient power transmission and to minimize the possibility of spoofing and eavesdropping. Tunable optical delays play an important role in the implementation of free space optical communication links. The primary challenge in implementing these systems is the active maintenance of coherent wave fronts across the system's optical aperture. For space applications, this aperture may he hundreds of meters in diameter. Spatial segmentation of a large aperture into smaller …
Dirac Theory Of Ring-Shaped Electron Distributions In Atoms, P Krekora, R E. Wagner, Q Su, Rainer Grobe
Dirac Theory Of Ring-Shaped Electron Distributions In Atoms, P Krekora, R E. Wagner, Q Su, Rainer Grobe
Faculty publications – Physics
The time-dependent Dirac equation is solved numerically on a space-time grid for an atom in a strong static magnetic field and a laser field. The resonantly induced relativistic motion of the atomic electron leads to a ringlike spatial probability density similar to the features that have been recently predicted [Wagner, Su, and Grobe, Phys. Rev. Lett. 84, 3282 (2000)] based on a phase-space method. We further demonstrate that spin-orbit coupling for a fast-moving electron in such an atom becomes significant and the time dependence of the spin can dephase even if initially aligned parallel to the direction of the static …