5,163 research outputs found
Spontaneous-emission suppression via multiphoton quantum interference
The spontaneous emission is investigated for an effective atomic two-level
system in an intense coherent field with frequency lower than the
vacuum-induced decay width. As this additional low-frequency field is assumed
to be intense, multiphoton processes may be induced, which can be seen as
alternative transition pathways in addition to the simple spontaneous decay.
The interplay of the various interfering transition pathways influences the
decay dynamics of the two-level system and may be used to slow down the
spontaneous decay considerably. We derive from first principles an expression
for the Hamiltonian including up to three-photon processes. This Hamiltonian is
then applied to a quantum mechanical simulation of the decay dynamics of the
two-level system. Finally, we discuss numerical results of this simulation
based on a rubidium atom and show that the spontaneous emission in this system
may be suppressed substantially.Comment: 18 pages, 7 figures, latest version with minor change
Double-EIT ground-state laser cooling without blue-sideband heating
We discuss a laser cooling scheme for trapped atoms or ions which is based on
double electromagnetically induced transparency (EIT) and makes use of a
four-level atom in tripod configuration. The additional fourth atomic state is
coupled by a strong coupling laser field to the usual three-level setup of
single-EIT cooling. This effectively allows to create two EIT structures in the
absorption spectrum of the system to be cooled, which may be controlled by the
coupling laser field parameters to cancel both the carrier- and the
blue-sideband excitations. In leading order of the Lamb-Dicke expansion, this
suppresses all heating processes. As a consequence, the double-EIT scheme can
be used to lower the cooling limit by almost two powers of the Lamb-Dicke
parameter as compared to single-EIT cooling.Comment: 7 pages, 3 figure
Tailoring superradiance to design artificial quantum systems
Cooperative phenomena arising due to the coupling of individual atoms via the
radiation field are a cornerstone of modern quantum and optical physics. Recent
experiments on x-ray quantum optics added a new twist to this line of research
by exploiting superradiance in order to construct artificial quantum systems.
However, so far, systematic approaches to deliberately design superradiance
properties are lacking, impeding the desired implementation of more advanced
quantum optical schemes. Here, we develop an analytical framework for the
engineering of single-photon superradiance in extended media applicable across
the entire electromagnetic spectrum, and show how it can be used to tailor the
properties of an artificial quantum system. This "reverse engineering" of
superradiance not only provides an avenue towards non-linear and quantum
mechanical phenomena at x-ray energies, but also leads to a unified view on and
a better understanding of superradiance across different physical systems.Comment: 6 pages + supplemental materia
Quantum correlations of an atomic ensemble via a classical bath
Somewhat surprisingly, quantum features can be extracted from a classical
bath. For this, we discuss a sample of three-level atoms in ladder
configuration interacting only via the surrounding bath, and show that the
fluorescence light emitted by this system exhibits non-classical properties.
Typical realizations for such an environment are thermal baths for microwave
transition frequencies, or incoherent broadband fields for optical transitions.
In a small sample of atoms, the emitted light can be switched from sub- to
super-poissonian and from anti-bunching to super-bunching controlled by the
mean number of atoms in the sample. Larger samples allow to generate
super-bunched light over a wide range of bath parameters and thus fluorescence
light intensities. We also identify parameter ranges where the fields emitted
on the two transitions are correlated or anti-correlated, such that the
Cauchy-Schwarz inequality is violated. As in a moderately strong baths this
violation occurs also for larger numbers of atoms, such samples exhibit
mesoscopic quantum effects.Comment: 4 page
Universality of the edge tunneling exponent of fractional quantum Hall liquids
Recent calculations of the edge tunneling exponents in quantum Hall states
appear to contradict their topological nature. We revisit this issue and find
no fundamental discrepancies. In a microscopic model of fractional quantum Hall
liquids with electron-electron interaction and confinement, we calculate the
edge Green's function via exact diagonalization. Our results for
and 2/3 suggest that in the presence of Coulomb interaction, the sharpness of
the edge and the strength of the edge confining potential, which can lead to
edge reconstruction, are the parameters that are relevant to the universality
of the electron tunneling I-V exponent.Comment: 5 pages, 3 figure
The IDEAL (Integrated Design and Engineering Analysis Languages) modeling methodology: Capabilities and Applications
The IDEAL (Integrated Design and Engineering Analysis Languages) modeling methodology has been formulated and applied over a five-year period. It has proven to be a unique, integrated approach utilizing a top-down, structured technique to define and document the system of interest; a knowledge engineering technique to collect and organize system descriptive information; a rapid prototyping technique to perform preliminary system performance analysis; and a sophisticated simulation technique to perform in-depth system performance analysis
Radiative Corrections to Multi-Level Mollow-Type Spectra
This paper is concerned with two rather basic phenomena: the incoherent
fluorescence spectrum of an atom driven by an intense laser field and the
coupling of the atom to the (empty) modes of the radiation field. The sum of
the many-photon processes gives rise to the inelastic part of the atomic
fluorescence, which, for a two-level system, has a well-known characteristic
three-peak structure known as the Mollow spectrum. From a theoretical point of
view, the Mollow spectrum finds a natural interpretation in terms of
transitions among laser-dressed states which are the energy eigenstates of a
second-quantized two-level system strongly coupled to a driving laser field. As
recently shown, the quasi-energies of the laser-dressed states receive
radiative corrections which are nontrivially different from the results which
one would expect from an investigation of the coupling of the bare states to
the vacuum modes. In this article, we briefly review the basic elements
required for the analysis of the dynamic radiative corrections, and we
generalize the treatment of the radiative corrections to the incoherent part of
the steady-state fluorescence to a three-level system consisting of 1S, 3P and
2S states.Comment: Dedicated to Prof. H. Walther on the occasion of his 70th birthda
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