34,149 research outputs found
Parametric Competition in non-autonomous Hamiltonian Systems
In this work we use the formalism of chord functions (\emph{i.e.}
characteristic functions) to analytically solve quadratic non-autonomous
Hamiltonians coupled to a reservoir composed by an infinity set of oscillators,
with Gaussian initial state. We analytically obtain a solution for the
characteristic function under dissipation, and therefore for the determinant of
the covariance matrix and the von Neumann entropy, where the latter is the
physical quantity of interest. We study in details two examples that are known
to show dynamical squeezing and instability effects: the inverted harmonic
oscillator and an oscillator with time dependent frequency. We show that it
will appear in both cases a clear competition between instability and
dissipation. If the dissipation is small when compared to the instability, the
squeezing generation is dominant and one can see an increasing in the von
Neumann entropy. When the dissipation is large enough, the dynamical squeezing
generation in one of the quadratures is retained, thence the growth in the von
Neumann entropy is contained
Exotic looped trajectories via quantum marking
We provide an analytical and theoretical study of exotic looped trajectories
(ELTs) in a double-slit interferometer with quantum marking. We use an excited
Rydberg-like atom and which-way detectors such as superconducting cavities,
just as in the Scully-Englert-Walther interferometer. We indicate appropriate
conditions on the atomic beam or superconducting cavities so that we determine
an interference pattern and fringe visibility exclusive from the ELTs. We
quantitatively describe our results for Rubidium atoms and propose this
framework as an alternative scheme to the double-slit experiment modified to
interfere only these exotic trajectories.Comment: 10 pages, 5 figure
Crystallization, data collection and data processing of maltose-binding protein (MalE) from the phytopathogen Xanthomonas axonopodis pv. citri
Maltose-binding protein is the periplasmic component of the ABC transporter
responsible for the uptake of maltose/maltodextrins. The Xanthomonas axonopodis
pv. citri maltose-binding protein MalE has been crystallized at 293 Kusing
the hanging-drop vapour-diffusion method. The crystal belonged to the
primitive hexagonal space group P6_122, with unit-cell parameters a = 123.59,
b = 123.59, c = 304.20 Ã…, and contained two molecules in the asymetric unit. It
diffracted to 2.24 Ã… resolution
Proposal for a single-molecule field-effect transistor for phonons
We propose a practical realization of a field-effect transistor for phonons.
Our device is based on a single ionic polymeric molecule and it gives
modulations as large as -25% in the thermal conductance for feasible
temperatures and electric field magnitudes. Such effect can be achieved by
reversibly switching the acoustic torsion mode into an optical mode through the
coupling of an applied electric field to the dipole moments of the monomers.
This device can pave the way to the future development of phononics at the
nanoscale or molecular scale
Phase-space reconstruction of an atomic chaotic system
We consider the dynamics of a single atom submitted to periodic pulses of a
far-detuned standing wave generated by a high-finesse optical cavity, which is
an atomic version of the well-known ``kicked rotor''. We show that the
classical phase-space map can be ``reconstructed'' by monitoring the
transmission of the cavity. We also studied the effect of spontaneous emission
on the reconstruction, and put limits to the maximum acceptable spontaneous
emission rate.Comment: 5 figures, submitted to PR
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