6,769 research outputs found
Kondo Resonance of a Microwave Photon
We emulate renormalization group models, such as the Spin-Boson Hamiltonian
or the anisotropic Kondo model, from a quantum optics perspective by
considering a superconducting device. The infra-red confinement involves photon
excitations of two tunable transmission lines entangled to an artificial
spin-1/2 particle or double-island charge qubit. Focusing on the propagation of
microwave light, in the underdamped regime of the Spin-Boson model, we identify
a many-body resonance where a photon is absorbed at the renormalized qubit
frequency and reemitted forward in an elastic manner. We also show that
asymptotic freedom of microwave light is reached by increasing the input signal
amplitude at low temperatures which allows the disappearance of the
transmission peak.Comment: Final Version: Main text and Supplementary Materia
When is electromagnetic spectrum fungible?
Fungibility is a common assumption for market-based spectrum management. In this paper, we explore the dimensions of practical fungibility of frequency bands from the point of view of the spectrum buyer who intends to use it. The exploration shows that fungibility is a complex, multidimensional concept that cannot casually be assumed. We develop two ideas for quantifying fungibility-(i) of a fungibility space in which the 'distance' between two slices of spectrum provides score of fungibility and (ii) a probabilistic score of fungibility. © 2012 IEEE
Dissipative Quantum Ising model in a cold atomic spin-boson mixture
Using cold bosonic atoms with two (hyperfine) ground states, we introduce a
spin-boson mixture which allows to implement the quantum Ising model in a
tunable dissipative environment. The first specie lies in a deep optical
lattice with tightly confining wells and forms a spin array; spin-up/down
corresponds to occupation by one/no atom at each site. The second specie forms
a superfluid reservoir. Different species are coupled coherently via laser
transitions and collisions. Whereas the laser coupling mimics a transverse
field for the spins, the coupling to the reservoir sound modes induces a
ferromagnetic (Ising) coupling as well as dissipation. This gives rise to an
order-disorder quantum phase transition where the effect of dissipation can be
studied in a controllable manner.Comment: 4 pages, 2 figures, 1 table; Title modified and cosmetic change
Revisiting CoRoT RR Lyrae stars: detection of period doubling and temporal variation of additional frequencies
We search for signs of period doubling in CoRoT RR Lyrae stars. The
occurrence of this dynamical effect in modulated RR Lyrae stars might help us
to gain more information about the mysterious Blazhko effect. The temporal
variability of the additional frequencies in representatives of all subtypes of
RR Lyrae stars is also investigated. We pre-process CoRoT light curves by
applying trend and jump correction and outlier removal. Standard Fourier
technique is used to analyze the frequency content of our targets and follow
the time dependent phenomena. The most comprehensive collection of CoRoT RR
Lyrae stars, including new discoveries is presented and analyzed. We found
alternating maxima and in some cases half-integer frequencies in four CoRoT
Blazhko RR Lyrae stars, as clear signs of the presence of period doubling. This
reinforces that period doubling is an important ingredient to understand the
Blazhko effect - a premise we derived previously from the Kepler RR Lyrae
sample. As expected, period doubling is detectable only for short time
intervals in most modulated RRab stars. Our results show that the temporal
variability of the additional frequencies in all RR Lyrae sub-types is
ubiquitous. The ephemeral nature and the highly variable amplitude of these
variations suggest a complex underlying dynamics of and an intricate interplay
between radial and possibly nonradial modes in RR Lyrae stars. The omnipresence
of additional modes in all types of RR Lyrae - except in non-modulated RRab
stars - implies that asteroseismology of these objects should be feasible in
the near future (Abridged).Comment: 20 pages, 13 figures, accepted for publication in A&
A new technological procedure using sucrose as porogen compound to manufacture porous biphasic calcium phosphate ceramics of appropriate micro- and macrostructure
In the domain of implantable materials, the porosity and pore size distribution of a material in contact with bone is decisive for bone ingrowth and thus the control of the porosity is of great interest. The use of a new porogen agent, i.e. sucrose is proposed to create a porosity in biphasic calcium phosphate blocks. The technological procedure is as follows: sucrose and mineral powder are mixed, then compressed by isostatic compression and sintering finally eliminates sucrose. Blocks obtained were compared to a manufactured product: Triosite® (Zimmer, Etupes, France) which porosity is created through a naphthalene sublimation process.Results have shown that the incorporation of sucrose allows the preparation of porous blocks with controlled porosity varying from 40 to 80% and with macro-, meso- and microporosity characteristics depending on the percentage of sucrose added as well as on the granulometry of both sucrose and mineral powder
Direct observation of hydrodynamization and local prethermalization
Hydrodynamics accurately describes relativistic heavy-ion collision
experiments well before local thermal equilibrium is established. This
unexpectedly rapid onset of hydrodynamics -- which takes place on the fastest
available timescale -- is called hydrodynamization. It occurs when an
interacting quantum system is quenched with an energy density that is much
greater than its initial energy density. During hydrodynamization, energy gets
redistributed across very different energy scales. Hydrodynamization precedes
local equilibration among momentum modes, which is local prethermalization to a
generalized Gibbs ensemble in nearly integrable systems or local thermalization
in non-integrable systems. Many theories of quantum dynamics postulate local
(pre)thermalization, but the associated timescale has not been quantitatively
studied. Here we use an array of 1D Bose gases to directly observe both
hydrodynamization and local prethermalization. After we apply a Bragg
scattering pulse, hydrodynamization is evident in the fast redistribution of
energy among distant momentum modes, which occurs on timescales associated with
the Bragg peak energies. Local prethermalization can be seen in the slower
redistribution of occupation among nearby momentum modes. We find that the time
scale for local prethermalization in our system is inversely proportional to
the momenta involved. During hydrodynamization and local prethermalization,
existing theories cannot quantitatively model our experiment. Exact theoretical
calculations in the Tonks-Girardeau limit show qualitatively similar features.Comment: 28 pages, 4 main figures, 8 extended data figure
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