1,885 research outputs found
Dynamical bistability in the driven circuit QED
We show that the nonlinear response of a driven circuit quantum
electrodynamics setup displays antiresonant multiphoton transitions, as
recently observed in a transmon qubit device. By including photon leaking, we
explain the lineshape by a perturbative and a semiclassical analysis. We derive
a bistable semiclassical quasienergy surface whose lowest quasienergy
eigenstate is squeezed, allowing for a squeezing-dependent local effective
temperature. We study the escape dynamics out of the metastable state and find
signatures of dynamical tunneling, similar as for the quantum Duffing
oscillator.Comment: submitted to PR
Topological edge states for disordered bosonic systems
Quadratic bosonic Hamiltonians over a one-particle Hilbert space can be
described by a Bogoliubov-de Gennes (BdG) Hamiltonian on a particle-hole
Hilbert space. In general, the BdG Hamiltonian is not selfadjoint, but only
-selfadjoint on the particle-hole space viewed as a Krein space.
Nevertheless, its energy bands can have non-trivial topological invariants like
Chern numbers or winding numbers. By a thorough analysis for tight-binding
models, it is proved that these invariants lead to bosonic edge modes which are
robust to a large class of possibly disordered perturbations. Furthermore,
general scenarios are presented for these edge states to be dynamically
unstable, even though the bulk modes are stable
Chimera states in small disordered optomechanical arrays
Synchronization of weakly-coupled non-linear oscillators is a ubiquitous
phenomenon that has been observed across the natural sciences. We study the
dynamics of optomechanical arrays - networks of mechanically compliant
structures that interact with the radiation pressure force - which are driven
to self-oscillation. These systems offer a convenient platform to study
synchronization phenomena and have potential technological applications. We
demonstrate that this system supports the existence of long-lived chimera
states, where parts of the array synchronize whilst others do not. Through a
combined numerical and analytical analysis we show that these chimera states
can only emerge in the presence of disorder.Comment: 4+ pages, 4 figures, comments very welcome
Logic Programming approaches for routing fault-free and maximally-parallel Wavelength Routed Optical Networks on Chip (Application paper)
One promising trend in digital system integration consists of boosting
on-chip communication performance by means of silicon photonics, thus
materializing the so-called Optical Networks-on-Chip (ONoCs). Among them,
wavelength routing can be used to route a signal to destination by univocally
associating a routing path to the wavelength of the optical carrier. Such
wavelengths should be chosen so to minimize interferences among optical
channels and to avoid routing faults. As a result, physical parameter selection
of such networks requires the solution of complex constrained optimization
problems. In previous work, published in the proceedings of the International
Conference on Computer-Aided Design, we proposed and solved the problem of
computing the maximum parallelism obtainable in the communication between any
two endpoints while avoiding misrouting of optical signals. The underlying
technology, only quickly mentioned in that paper, is Answer Set Programming
(ASP). In this work, we detail the ASP approach we used to solve such problem.
Another important design issue is to select the wavelengths of optical
carriers such that they are spread across the available spectrum, in order to
reduce the likelihood that, due to imperfections in the manufacturing process,
unintended routing faults arise. We show how to address such problem in
Constraint Logic Programming on Finite Domains (CLP(FD)).
This paper is under consideration for possible publication on Theory and
Practice of Logic Programming.Comment: Paper presented at the 33nd International Conference on Logic
Programming (ICLP 2017), Melbourne, Australia, August 28 to September 1,
2017. 16 pages, LaTeX, 5 figure
Pseudomagnetic fields for sound at the nanoscale
There is a growing effort in creating chiral transport of sound waves.
However, most approaches so far are confined to the macroscopic scale. Here, we
propose a new approach suitable to the nanoscale which is based on
pseudomagnetic fields. These fields are the analogon for sound of the
pseudomagnetic field for electrons in strained graphene. In our proposal, they
are created by simple geometrical modifications of an existing and
experimentally proven phononic crystal design, the snowflake crystal. This
platform is robust, scalable, and well-suited for a variety of excitation and
readout mechanisms, among them optomechanical approaches
Photon-assisted confinement-induced resonances for ultracold atoms
We solve the two-particle s-wave scattering for an ultracold atom gas
confined in a quasi-one-dimensional trapping potential which is periodically
modulated. The interaction between the atoms is included in terms of Fermi's
pseudopotential. For a modulated isotropic transverse harmonic confinement, the
atomic center of mass and relative degrees of freedom decouple and an exact
solution is possible. We use the Floquet approach to show that additional
photon-assisted resonant scattering channels open up due to the harmonic
modulation. Applying the Bethe-Peierls boundary condition, we obtain the
general scattering solution of the time-dependent Schr\"odinger equation which
is universal at low energies. The binding energies and the effective
one-dimensional scattering length can be controlled by the external driving
Topological Phases of Sound and Light
Topological states of matter are particularly robust, since they exploit
global features insensitive to local perturbations. In this work, we describe
how to create a Chern insulator of phonons in the solid state. The proposed
implementation is based on a simple setting, a dielectric slab with a suitable
pattern of holes. Its topological properties can be wholly tuned in-situ by
adjusting the amplitude and frequency of a driving laser that controls the
optomechanical interaction between light and sound. The resulting chiral,
topologically protected phonon transport along the edges can be probed
completely optically. Moreover, we identify a regime of strong mixing between
photon and phonon excitations, which gives rise to a large set of different
topological phases. This would be an example of a Chern insulator produced from
the interaction between two physically very different particle species, photons
and phonons
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