David A. Harmin

Theory of the Stark Effect in Highly Excited Atoms

The physics of a Rydberg atom in a uniform dc electric field is a solvable problem [1]. The theory underlying this assertion has several components, which in turn rely on certain approximations, but the machinery as a whole has been put to the experimental test and found to be accurate to a level of up to 10 ppm [2]. The broad assumptions that allow one to investigate atoms, ions, and perhaps even molecules with some success are made in the spirit of multichannel quantum-defect theory (MQDT) [3, 4]. Such a treatment is appropriate to Rydberg systems, wherein one electron is significantly more excited than any of the others. The finer structural aspects of the atom + field system—as reflected in the detailed features of an observable spectrum—are associated with the highly excited electron only. The thrust of the present approach is to obtain a complete description of an excited hydrogen atom in an electric field, and to consider modifications to the atomic spectrum introduced by the presence of a nonhydrogenic atom’s core.

Multichannel quantum‐defect theory of the Stark effect

The spectra of hydrogen and nonhydrogenic Rydberg atoms in a dc electric field F are discussed in the framework of multichannel quantum defect theory (MQDT). Nonhydrogenic, many‐electron interactions are confined to the atomic core, where the field’s influence is nil. The Rydberg electron’s wave function is sensitive to F, but only outside the core. Hydrogen‐Stark eigenfunctions in a parabolic basis are required to represent the excited electron at r≫rF where z=−rF marks the classical saddle point and classical ionization limit ecil=−2√F (a.u.). A frame transformation connects spherical and parabolic bases for hydrogen. WKB phase and tunnelling integrals parametrize the field’s effects on wave function phases and amplitudes, and determine the hydrogenic density of states HF. The atom’s reaction matrix K (including quantum defects) then determines the nonhydrogenic density of states DF. At e<ecil, DF has a quasi‐discrete spectrum of Stark‐split and ‐broadened levels, whereas at e≳ecil all levels ionize. Th...

Duality in Two-Ways Interferometers: the Symmetric Quanton-Detecton System

Two entangled two-level system (or qubits) is the fundamental ‘brick’ in the construcion of quantum logic gates, which are the base of quantum networks. Quantum entanglement is also at the core of the duality principle relating fringe visibility and acquisition of which way information in a two-ways interferometer. We present here a quantum logic gate — the Symmetric Quanton-Detecton System, for which each qubit can play the role of quanton or which-way detector. Applying the results of Englert [Phys. Rev. Lett. 77, 2154 (1996).] we derive a pair of coupled duality relations for the system.