225 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 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
Optomechanical position detection enhanced by de-amplification using intracavity squeezing
It has been predicted and experimentally demonstrated that by injecting
squeezed light into an optomechanical device it is possible to enhance the
precision of a position measurement. Here, we present a fundamentally different
approach where the squeezing is created directly inside the cavity by a
nonlinear medium. Counterintuitively, the enhancement of the signal to noise
ratio works by de-amplifying precisely the quadrature that is sensitive to the
mechanical motion without losing quantum information. This enhancement works
for systems with a weak optomechanical coupling and/or strong mechanical
damping. This could allow for larger mechanical bandwidth of quantum limited
detectors based on optomechanical devices. Our approach can be
straightforwardly extended to Quantum Non Demolition (QND) qubit detection.Comment: references added, slight change
Optomechanical creation of magnetic fields for photons on a lattice
We propose using the optomechanical interaction to create artificial magnetic
fields for photons on a lattice. The ingredients required are an optomechanical
crystal, i.e. a piece of dielectric with the right pattern of holes, and two
laser beams with the right pattern of phases. One of the two proposed schemes
is based on optomechanical modulation of the links between optical modes, while
the other is an lattice extension of optomechanical wavelength-conversion
setups. We illustrate the resulting optical spectrum, photon transport in the
presence of an artificial Lorentz force, edge states, and the photonic
Aharonov-Bohm effect. Moreover, wWe also briefly describe the gauge fields
acting on the synthetic dimension related to the phonon/photon degree of
freedom. These can be generated using a single laser beam impinging on an
optomechanical array
Confinement-induced resonances for a two-component ultracold atom gas in arbitrary quasi-one-dimensional traps
We solve the two-particle s-wave scattering problem for ultracold atom gases
confined in arbitrary quasi-one-dimensional trapping potentials, allowing for
two different atom species. As a consequence, the center-of-mass and relative
degrees of freedom do not factorize. We derive bound-state solutions and obtain
the general scattering solution, which exhibits several resonances in the 1D
scattering length induced by the confinement. We apply our formalism to two
experimentally relevant cases: (i) interspecies scattering in a two-species
mixture, and (ii) the two-body problem for a single species in a non-parabolic
trap.Comment: 22 pages, 3 figure
Rapid Exploration of Topological Band Structures using Deep Learning
The design of periodic nanostructures allows to tailor the transport of photons, phonons, and matter waves for specific applications. Recent years have seen a further expansion of this field by engineering topological properties. However, what is missing currently are efficient ways to rapidly explore and optimize band structures and to classify their topological characteristics, for arbitrary unit cell geometries. In this work, we show how deep learning can address this challenge. We introduce an approach where a neural network first maps the geometry to a tight-binding model. This allows us to exploit any underlying space group and predict the symmetries of Bloch waves. We demonstrate how that helps to rapidly categorize a large set of geometries in terms of their band representations, identifying designs for fragile topologies. Engineering of domain walls and optimization are also accelerated by orders of magnitude. The approach is general enough to permit future applications to the geometry discovery in other classes of materials (e.g. active and nonlinear metamaterials)
Tunneling-induced fractal transmission in Valley Hall waveguides
The Valley Hall effect provides a popular route to engineer robust waveguides for bosonic excitations such a photons and phonons. The almost complete absence of backscattering in many experiments has its theoretical underpinning in a smooth-envelope approximation that neglects large momentum transfer and is accurate only for small bulk band gaps and/or smooth domain walls. For larger bulk band gaps and hard domain walls backscattering is expected to become significant. Here, we show that in this experimentally relevant regime, the reflection of a wave at a sharp corner becomes highly sensitive on the orientation of the outgoing waveguide relative to the underlying lattice. Enhanced backscattering can be understood as being triggered by resonant tunneling transitions in quasimomentum space. Tracking the resonant tunneling energies as a function of the waveguide orientation reveals a self-repeating fractal pattern that is also imprinted in the density of states and the backscattering rate at a sharp corner
Phase Space Crystal Vibrations: Chiral Edge States with Preserved Time-reversal Symmetry
Chiral transport along edge channels in Chern insulators represents the most robust version of topological transport, but it usually requires breaking of the physical time-reversal symmetry. In this work, we introduce a different mechanism that foregoes this requirement, based on the combination of the symplectic geometry of phase space and interactions. Starting from a honeycomb phase-space crystal of atoms, which can be generated by periodic driving of a one-dimensional interacting quantum gas, we show that the resulting vibrational lattice waves have topological properties. Our work provides a new platform to study topological many-body physics in dynamical systems
Consumer attitudes and preference exploration towards fresh-cut salads using best–worst scaling and latent class analysis
This research explored the preferences and buying habits of a sample of 620 consumers of fresh-cut, ready-to-eat salads. A best–worst scaling approach was used to measure the level of preference stated by individuals regarding 12 attributes for quality (intrinsic, extrinsic and credence) of fresh-cut salads. The experiment was carried out through direct interviews at several large-scale retail outlets in the Turin metropolitan area (north-west of Italy). Out of the total number of questioned consumers, 35% said they did not consume fresh-cut salads. On the contrary, the rest of the involved sample expressed the highest degree of preference towards the freshness/appearance attribute, followed by the expiration date and the brand. On the contrary, attributes such as price, organic certification and food safety did not emerge as discriminating factors in consumer choices. Additionally, five clusters of consumers were identified, whose preferences are related both to purchasing styles and socio-demographic variables. In conclusion, this research has highlighted the positive attitude of consumers towards quality products backed by a brand, providing ideas for companies to improve within this sector and implement strategies to answer the needs of a new segment of consumers, by determining market opportunities that aim to strengthen local brands
- …