119 research outputs found
Criminal Law—Court Orders Broad Relief to Inmates Throughout the Virginia Penal System Where Constitutional Rights Have Been Violated.
Landman v. Royster, 333 F. Supp. 621 (E.D. Va. 1971)
Operator Ordering in Quantum Radiative Processes
In this work we reexamine quantum electrodynamics of atomic eletrons in the
Coulomb gauge in the dipole approximation and calculate the shift of atomic
energy levels in the context of Dalibard, Dupont-Roc and Cohen-Tannoudji (DDC)
formalism by considering the variation rates of physical observables. We then
analyze the physical interpretation of the ordering of operators in the dipole
approximation interaction Hamiltonian in terms of field fluctuations and
self-reaction of atomic eletrons, discussing the arbitrariness in the
statistical functions in second order bound-state perturbation theory.Comment: Latex file, 12 pages, no figures, includes PACS numbers and minor
changes in the text with the addition of a new sectio
Spontaneous and stimulated emission tuning characteristics of a Josephson junction in a microcavity
We have investigated theoretically the tuning characteristics of a Josephson
junction within a microcavity for one-photon spontaneous emission and for
one-photon and two-photon stimulated emission. For spontaneous emission, we
have established the linear relationship between the magnetic induction and the
voltage needed to tune the system to emit at resonant frequencies. For
stimulated emission, we have found an oscillatory dependence of the emission
rate on the initial Cooper pair phase difference and the phase of the applied
field. Under specific conditions, we have also calculated the values of the
applied radiation amplitude for the first few emission maxima of the system and
for the first five junction-cavity resonances for each process. Since the
emission of photons can be controlled, it may be possible to use such a system
to produce photons on demand. Such sources will have applications in the fields
of quantum cryptography, communications and computation
Ac-cotunneling through an interacting quantum dot under a magnetic field
We analyze inelastic cotunneling through an interacting quantum dot subject
to an ambient magnetic field in the weak tunneling regime under a non-adiabatic
time-dependent bias-voltage. Our results clearly exhibit photon-assisted
satellites and an overall suppression of differential conductance with
increasing driving amplitude, which is consistent with experiments. We also
predict a zero-anomaly in differential conductance under an appropriate driving
frequency.Comment: Phys. Lett. A (in press
Spontaneous excitation of an accelerated atom: The contributions of vacuum fluctuations and radiation reaction
We consider an atom in interaction with a massless scalar quantum field. We
discuss the structure of the rate of variation of the atomic energy for an
arbitrary stationary motion of the atom through the quantum vacuum. Our main
intention is to identify and to analyze quantitatively the distinct
contributions of vacuum fluctuations and radiation reaction to the spontaneous
excitation of a uniformly accelerated atom in its ground state. This gives an
understanding of the role of the different physical processes underlying the
Unruh effect. The atom's evolution into equilibrium and the Einstein
coefficients for spontaneous excitation and spontaneous emission are
calculated.Comment: 13 pages, KONS-RGKU-94-09, to appear in Phys. Rev.
Radiative energy shifts of accelerated atoms
We consider the influence of acceleration on the radiative energy shifts of
atoms in Minkowski space. We study a two-level atom coupled to a scalar quantum
field. Using a Heisenberg picture approach, we are able to separate the
contributions of vacuum fluctuations and radiation reaction to the Lamb shift
of the two-level atom. The resulting energy shifts for the special case of a
uniformly accelerated atom are then compared with those of an atom at rest.Comment: 12 pages, Latex, 1 figure as uuencoded eps file, shorter version will
appear in Phys. Rev.
Resonant dipole-dipole interaction in the presence of dispersing and absorbing surroundings
Within the framework of quantization of the macroscopic electromagnetic
field, equations of motion and an effective Hamiltonian for treating both the
resonant dipole-dipole interaction between two-level atoms and the resonant
atom-field interaction are derived, which can suitably be used for studying the
influence of arbitrary dispersing and absorbing material surroundings on these
interactions. The theory is applied to the study of the transient behavior of
two atoms that initially share a single excitation, with special emphasis on
the role of the two competing processes of virtual and real photon exchange in
the energy transfer between the atoms. In particular, it is shown that for weak
atom-field interaction there is a time window, where the energy transfer
follows a rate regime of the type obtained by ordinary second-order
perturbation theory. Finally, the resonant dipole-dipole interaction is shown
to give rise to a doublet spectrum of the emitted light for weak atom-field
interaction and a triplet spectrum for strong atom-field interaction.Comment: 15 pages, 1 figure, RevTE
The Dipole Coupling of Atoms and Light in Gravitational Fields
The dipole coupling term between a system of N particles with total charge
zero and the electromagnetic field is derived in the presence of a weak
gravitational field. It is shown that the form of the coupling remains the same
as in flat space-time if it is written with respect to the proper time of the
observer and to the measurable field components. Some remarks concerning the
connection between the minimal and the dipole coupling are given.Comment: 10 pages, LaTe
Squeezed Light Generation in Nonlinear System with Chaotic Dynamics
The squeezing in a nonlinear system with chaotic dynamics is considered. The
model describing interaction of collection of two-level atoms with a
single-mode of self-consistent field and an external field is analyzed. It is
shown that in the semiclassical limit, in contrast to the regular behaviour,
the chaotic dynamics result in: (i) an increase in squeezing, (ii) unstable
squeezing and contraction of time intervals of squeezing on large enough times.
The possibility of the experimental observation of the described effects is
discussed.Comment: 12 pages, RevTEX (EPSF-style), 6 figure
Quantum field theory of cooperative atom response: Low light intensity
We study the interactions of a possibly dense and/or quantum degenerate gas
with driving light. Both the atoms and the electromagnetic fields are
represented by quantum fields throughout the analysis. We introduce a field
theory version of Markov and Born approximations for the interactions of light
with matter, and devise a procedure whereby certain types of products of atom
and light fields may be put to a desired, essentially normal, order. In the
limit of low light intensity we find a hierarchy of equations of motion for
correlation functions that contain one excited-atom field and one, two, three,
etc., ground state atom fields. It is conjectured that the entire linear
hierarchy may be solved by solving numerically the classical equations for the
coupled system of electromagnetic fields and charged harmonic oscillators. We
discuss the emergence of resonant dipole-dipole interactions and collective
linewidths, and delineate the limits of validity of the column density approach
in terms of non-cooperative atoms by presenting a mathematical example in which
this approach is exact.Comment: 35 pages, RevTe
- …