796 research outputs found
On the ubiquity of Beutler-Fano profiles: from scattering to dissipative processes
Fano models - consisting of a Hamiltonian with discrete-continuous spectrum -
are one of the basic toy models in spectroscopy. They have been succesfull in
explaining the lineshape of experiments in atomic physics and condensed matter.
These models however have largely been out of the scope of dissipative
dynamics, with ony a handful of works considering the effect of a thermal bath.
Yet in nanostructures and condensed matter systems, dissipation strongly
modulates the dynamics. In this article, we present an overview of the
theoretical works dealing with Fano interferences coupled to a thermal bath and
compare them to the scattering formalism. We provide the solution to any
discrete-continuous Hamiltonian structure within the wideband approximation
coupled to a Markovian bath. In doing so, we update the toy models that have
been available for unitary evolution since the 1960s. We find that the Fano
lineshape is preserved as long as we allow a rescaling of the parameters, and
an additional Lorentzian contribution that reflects the destruction of the
interference by dephasings. We discuss the pertinence of each approach -
dissipative and unitary - to different experimental setups: scattering,
transport and spectroscopy of dissipative systems. We finish by discussing the
current limitations of the theories due to the wideband approximation and the
memory effects of the bath.Comment: Expanded bibliography, minor typos correcte
Introducing conflict as the microfoundation of organizational ambidexterity
This article contributes to our understanding of organizational ambidexterity by introducing conflict as its microfoundation. Existing research distinguishes between three approaches to how organizations can be ambidextrous, that is, engage in both exploitation and exploration. They may sequentially shift the strategic focus of the organization over time, they may establish structural arrangements enabling the simultaneous pursuit of being both exploitative and explorative, or they may provide a supportive organizational context for ambidextrous behavior. However, we know little about how exactly ambidexterity is accomplished and managed. We argue that ambidexterity is a dynamic and conflict-laden phenomenon, and we locate conflict at the level of individuals, units, and organizations. We develop the argument that conflicts in social interaction serve as the microfoundation to organizing ambidexterity, but that their function and type vary across the different approaches toward ambidexterity. The perspective developed in this article opens up promising research avenues to examine how organizations purposefully manage ambidexterity
Bell-type inequalities for cold heteronuclear molecules
We introduce Bell-type inequalities allowing for non-locality and
entanglement tests with two cold heteronuclear molecules. The proposed
inequalities are based on correlations between each molecule spatial
orientation, an observable which can be experimentally measured with present
day technology. Orientation measurements are performed on each subsystem at
diferent times. These times play the role of the polarizer angles in Bell tests
realized with photons. We discuss the experimental implementations of the
proposed tests, which could also be adapted to other high dimensional quantum
angular momenta systems.Comment: 4 page
Classification of Dark States in Multi-level Dissipative Systems
Dark states are eigenstates or steady-states of a system that are decoupled
from the radiation. Their use, along with associated techniques such as
Stimulated Raman Adiabatic Passage, has extended from atomic physics where it
is an essential cooling mechanism, to more recent versions in condensed phase
where it can increase the coherence times of qubits. These states are often
discussed in the context of unitary evolution and found with elegant methods
exploiting symmetries, or via the Bruce-Shore transformation. However, the link
with dissipative systems is not always transparent, and distinctions between
classes of CPT are not always clear. We present a detailed overview of the
arguments to find stationary dark states in dissipative systems, and examine
their dependence on the Hamiltonian parameters, their multiplicity and purity.
We find a class of dark states that depends not only on the detunings of the
lasers but also on their relative intensities. We illustrate the criteria with
the more complex physical system of the hyperfine transitions of Rb and
show how a knowledge of the dark state manifold can inform the preparation of
pure states.Comment: additional example
Optimally Controlled Field-Free Orientation of the Kicked Molecule
Efficient and long-lived field-free molecular orientation is achieved using
only two kicks appropriately delayed in time. The understanding of the
mechanism rests upon a molecular target state providing the best efficiency
versus persistence compromise. An optimal control scheme is referred to for
fixing the free parameters (amplitudes and the time delay between them). The
limited number of kicks, the robustness and the transposability to different
molecular systems advocate in favor of the process, when considering its
experimental feasibility.Comment: 5 pages, 2 figures (version 2 contains some minor additions and
corrects many misprints
Fano-Liouville Spectral Signatures in Open Quantum Systems
The scattering amplitude from a set of discrete states coupled to a continuum
became known as the Fano profile, characteristic for its asymmetric lineshape
and originally investigated in the context of photoionization. The generality
of the model, and the proliferation of engineered nanostructures with confined
states gives immense success to the Fano lineshape, which is invoked whenever
an asymmetric lineshape is encountered. However, many of these systems do not
conform to the initial model worked out by Fano in that i) they are subject to
dissipative processes and ii) the observables are not entirely analogous to the
ones measured in the original photoionization experiments. In this letter, we
work out the full optical response of a Fano model with dissipation. We find
that the exact result for absorption, Raman, Rayleigh and fluorescence emission
is a modified Fano profile where the typical lineshape has an additional
Lorentzian contribution. Expressions to extract model parameters from a set of
relevant observables are given.Comment: corrected typo
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