40 research outputs found
Interference-induced splitting of resonances in spontaneous emission
We study the resonance fluorescence from a coherently driven four-level atom
in the Y-type configuration. The effects of quantum interference induced by
spontaneous emission on the fluorescence properties of the atom are
investigated. It is found that the quantum interference resulting from cascade
emission decays of the atom leads to a splitting of resonances in the excited
level populations calculated as a function of light detuning. For some
parameters, interference assisted enhancement of inner sidebands and narrowing
of central peaks may also occur in the fluorescence spectrum. We present a
physical understandingof our numerical results using the dressed state
description of the atom-light interaction.Comment: 7 pages including 7 figure
An analysis of dynamical suppression of spontaneous emission
It has been shown recently [see, for example, S.-Y. Zhu and M. O. Scully,
Phys. Rev. Lett. {\bf 76}, 388 (1996)] that a dynamical suppression of
spontaneous emission can occur in a three-level system when an external field
drives transitions between a metastable state and {\em two} decaying states.
What is unusual in the decay scheme is that the decaying states are coupled
directly by the vacuum radiation field. It is shown that decay dynamics
required for total suppression of spontaneous emission necessarily implies that
the level scheme is isomorphic to a three-level lambda system, in which the
lower two levels are {\em both} metastable, and each is coupled to the decaying
state. As such, the total suppression of spontaneous emission can be explained
in terms of conventional dark states and coherent population trapping.Comment: 8 pages, 3 figure
Entanglement for a Bimodal Cavity Field Interacting with a Two-Level Atom
Negativity has been adopted to investigate the entanglement in a system
composed of a two-level atom and a two-mode cavity field. Effects of Kerr-like
medium and the number of photon inside the cavity on the entanglement are
studied. Our results show that atomic initial state must be superposed, so that
the two cavity field modes can be entangled. Moreover, we also conclude that
the number of photon in the two cavity mode should be equal. The interaction
between modes, namely, the Kerr effect, has a significant negative
contribution. Note that the atom frequency and the cavity frequency have an
indistinguishable effect, so a corresponding approximation has been made in
this article. These results may be useful for quantum information in optics
systems.Comment: Accepted by Commun. Theor. Phy
Influence of damping on the vanishing of the electro-optic effect in chiral isotropic media
Using first principles, it is demonstrated that radiative damping alone
cannot lead to a nonvanishing electro-optic effect in a chiral isotropic
medium. This conclusion is in contrast with that obtained by a calculation in
which damping effects are included using the standard phenomenological model.
We show that these predictions differ because the phenomenological damping
equations are valid only in regions where the frequencies of the applied
electromagnetic fields are nearly resonant with the atomic transitions. We also
show that collisional damping can lead to a nonvanishing electrooptic effect,
but with a strength sufficiently weak that it is unlikely to be observable
under realistic laboratory conditions
Supersymmetric Jaynes-Cummings model and its exact solutions
The super-algebraic structure of a generalized version of the Jaynes-Cummings
model is investigated. We find that a Z2 graded extension of the so(2,1) Lie
algebra is the underlying symmetry of this model. It is isomorphic to the
four-dimensional super-algebra u(1/1) with two odd and two even elements.
Differential matrix operators are taken as realization of the elements of the
superalgebra to which the model Hamiltonian belongs. Several examples with
various choices of superpotentials are presented. The energy spectrum and
corresponding wavefunctions are obtained analytically.Comment: 12 pages, no figure
Near-surface imaging using coincident seismic and GPR data
This is the publisher's version, also available electronically from "http://onlinelibrary.wiley.com".In many near-surface applications, detailed subsurface characterization is important. Characterization often is obtained using ground-penetrating radar (GPR) or shallow seismic-reflection (SSR) imaging methods, depending upon depth of interest and surficial geology. Each method responds to different physical properties; thus, each may produce different images of the same near-surface volume. By incorporating the two methods, we generated a cross-section of the subsurface at an alluvial test site and identified the depths of three interfaces accurately to ±5 cm. We present here experimental results and examples of SSR and GPR images obtained along the same traverse, showing coincident and noncoincident reflections from multiple interfaces within 3 m of the surface
Polariton Analysis of a Four-Level Atom Strongly Coupled to a Cavity Mode
We present a complete analytical solution for a single four-level atom
strongly coupled to a cavity field mode and driven by external coherent laser
fields. The four-level atomic system consists of a three-level subsystem in an
EIT configuration, plus an additional atomic level; this system has been
predicted to exhibit a photon blockade effect. The solution is presented in
terms of polaritons. An effective Hamiltonian obtained by this procedure is
analyzed from the viewpoint of an effective two-level system, and the dynamic
Stark splitting of dressed states is discussed. The fluorescence spectrum of
light exiting the cavity mode is analyzed and relevant transitions identified.Comment: 12 pages, 9 figure
Cavity-induced coherence effects in spontaneous emission from pre-Selection of polarization
Spontaneous emission can create coherences in a multilevel atom having close
lying levels, subject to the condition that the atomic dipole matrix elements
are non-orthogonal. This condition is rarely met in atomic systems. We report
the possibility of bypassing this condition and thereby creating coherences by
letting the atom with orthogonal dipoles to interact with the vacuum of a
pre-selected polarized cavity mode rather than the free space vacuum. We derive
a master equation for the reduced density operator of a model four level atomic
system, and obtain its analytical solution to describe the interference
effects. We report the quantum beat structure in the populations.Comment: 6 pages in REVTEX multicolumn format, 5 figures, new references
added, journal reference adde
Entangled two cavity modes preparation via a two-photon process
We propose a scheme for entangling two field modes in two high-Q optical
cavities. Making use of a virtual two-photon process, our scheme achieves
maximally entangled states without any real transitions of atomic internal
states, hence it is immune to the atomic decay.Comment: 4 pages, latex, 7 figure
The revival-collapse phenomenon in the quadrature field components of the two-mode multiphoton Jaynes-Cummings model
In this paper we consider a system consisting of a two-level atom in an
excited state interacting with two modes of a radiation field prepared
initially in -photon coherent states. This system is described by two-mode
multiphoton (, i.e., ) Jaynes-Cummings model (JCM). For this system
we investigate the occurrence of the revival-collapse phenomenon (RCP) in the
evolution of the single-mode, two-mode, sum and difference quadrature
squeezing. We show that there is a class of states for which all these types of
squeezing exhibit RCP similar to that involved in the corresponding atomic
inversion. Also we show numerically that the single-mode squeezing of the first
mode for provides RCP similar to that of the atomic inversion
of the case , however, sum and difference squeezing give
partial information on that case. Moreover, we show that single-mode, two-mode
and sum squeezing for the case provide information on the
atomic inversion of the single-mode two-photon JCM. We derive the rescaled
squeezing factors giving accurate information on the atomic inversion for all
cases. The consequences of these results are that the homodyne and heterodyne
detectors can be used to detect the RCP for the two-mode JCM.Comment: 18 pages, 6 figure