4,304 research outputs found
Control over few photon pulses by a time-periodic modulation of the photon-emitter coupling
We develop a Floquet scattering formalism for the description of
quasistationary states of microwave photons in a one-dimensional waveguide
interacting with a nonlinear cavity by means of a periodically modulated
coupling. This model is inspired by the recent progress in engineering of
tunable coupling schemes with superconducting qubits. We argue that our model
can realize the quantum analogue of an optical chopper. We find strong periodic
modulations of the transmission and reflection envelopes in the scattered
few-photon pulses, including photon compression and blockade, as well as
dramatic changes in statistics. Our theoretical analysis allows us to explain
these non-trivial phenomena as arising from non-adiabatic memory effects.Comment: 12 pages, 6 figures. arXiv admin note: substantial text overlap with
arXiv:1603.0549
Non-adiabatic effects in periodically driven-dissipative open quantum systems
We present a general method to calculate the quasi-stationary state of a
driven-dissipative system coupled to a transmission line (and more generally,
to a reservoir) under periodic modulation of its parameters. Using Floquet's
theorem, we formulate the differential equation for the system's density
operator which has to be solved for a single period of modulation. On this
basis we also provide systematic expansions in both the adiabatic and
high-frequency regime. Applying our method to three different systems -- two-
and three-level models as well as the driven nonlinear cavity -- we propose
periodic modulation protocols of parameters leading to a temporary suppression
of effective dissipation rates, and study the arising non-adiabatic features in
the response of these systems.Comment: 12 pages, 8 figure
Using superlattice potentials to probe long-range magnetic correlations in optical lattices
In Pedersen et al. (2011) we proposed a method to utilize a temporally
dependent superlattice potential to mediate spin-selective transport, and
thereby probe long and short range magnetic correlations in optical lattices.
Specifically this can be used for detecting antiferromagnetic ordering in
repulsive fermionic optical lattice systems, but more generally it can serve as
a means of directly probing correlations among the atoms by measuring the mean
value of an observable, the number of double occupied sites. Here, we provide a
detailed investigation of the physical processes which limit the effectiveness
of this "conveyer belt method". Furthermore we propose a simple ways to improve
the procedure, resulting in an essentially perfect (error-free) probing of the
magnetic correlations. These results shows that suitably constructed
superlattices constitute a promising way of manipulating atoms of different
spin species as well as probing their interactions.Comment: 12 pages, 9 figure
Quantum Interference in Off-Resonant Transport through Single Molecules
We provide a simple set of rules for predicting interference effects in
off-resonant transport through single-molecule junctions. These effects fall in
two classes, showing respectively an odd or an even number of nodes in the
linear conductance within a given molecular charge state, and we demonstrate
how to decide the interference class directly from the contacting geometry. For
neutral alternant hydrocarbons, we employ the Coulson-Rushbrooke-McLachlan
pairing theorem to show that the interference class is decided simply by
tunneling on and off the molecule from same, or different sublattices. More
generally, we investigate a range of smaller molecules by means of exact diag-
onalization combined with a perturbative treatment of the molecule-lead tunnel
coupling. While these results generally agree well with GW calculations, they
are shown to be at odds with simpler mean-field treatments. For molecules with
spin-degenerate ground states, we show that for most junctions, interference
causes no transmission nodes, but argue that it may lead to a non-standard
gate-dependence of the zero-bias Kondo resonance.Comment: 12 pages, 7 figure
Controllability and universal three-qubit quantum computation with trapped electron states
We show how to control and perform universal three-qubit quantum computation
with trapped electron quantum states. The three qubits are the electron spin,
and the first two quantum states of the cyclotron and axial harmonic
oscillators. We explicitly show how the universal gates can be performed. As an
example of a non-trivial quantum algorithm, we outline the implementation of
the Deutsch-Jozsa algorithm in this system.Comment: 4 pages, 1 figure. Typos corrected. The original publication is
available at http://www.springerlink.co
Thermodynamics of Heat Shock Response
Production of heat shock proteins are induced when a living cell is exposed
to a rise in temperature. The heat shock response of protein DnaK synthesis in
E.coli for temperature shifts from temperature T to T plus 7 degrees,
respectively to T minus 7 degrees is measured as function of the initial
temperature T. We observe a reversed heat shock at low T. The magnitude of the
shock increases when one increase the distance to the temperature , thereby mimicking the non monotous stability of proteins at low
temperature. Further we found that the variation of the heat shock with T
quantitatively follows the thermodynamic stability of proteins with
temperature. This suggest that stability related to hot as well as cold
unfolding of proteins is directly implemented in the biological control of
protein folding. We demonstrate that such an implementation is possible in a
minimalistic chemical network.Comment: To be published in Physical Review Letter
Testing "microscopic" theories of glass-forming liquids
We assess the validity of "microscopic" approaches of glass-forming liquids
based on the sole k nowledge of the static pair density correlations. To do so
we apply them to a benchmark provided by two liquid models that share very
similar static pair density correlation functions while disp laying distinct
temperature evolutions of their relaxation times. We find that the approaches
are unsuccessful in describing the difference in the dynamical behavior of the
two models. Our study is not exhausti ve, and we have not tested the effect of
adding corrections by including for instance three-body density correlations.
Yet, our results appear strong enough to challenge the claim that the slowd own
of relaxation in glass-forming liquids, for which it is well established that
the changes of the static structure factor with temperature are small, can be
explained by "microscopic" appr oaches only requiring the static pair density
correlations as nontrivial input.Comment: 10 pages, 7 figs; Accepted to EPJE Special Issue on The Physics of
Glasses. Arxiv version contains an addendum to the appendix which does not
appear in published versio
Change management: The case of the elite sport performance team
The effective and efficient implementation of change is often required for both successful performance and management survival across a host of contemporary domains. However, although of major theoretical and practical significance, research to date has overlooked the application of change management (hereafter CM) knowledge to the elite sport performance team environment. Considering that the success of ‘off-field’ sports businesses are largely dependent on the performances of their ‘on-field’ team, this article explores the application of current CM theorizing to this specific setting and the challenges facing its utility. Accordingly, we identify the need and importance of developing theory specific to this area, with practical application in both sport and business, through examination of current knowledge and identification of the domain's unique, dynamic and contested properties. Markers of successful change are then suggested to guide initial enquiry before the article concludes with proposed lines of research which may act to provide a valid and comprehensive theoretical account of CM to optimize the research and practice of those working in the field
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