176 research outputs found
Hybrid quantum magnetism in circuit-QED: from spin-photon waves to many-body spectroscopy
We introduce a model of quantum magnetism induced by the non-perturbative
exchange of microwave photons between distant superconducting qubits. By
interconnecting qubits and cavities, we obtain a spin-boson lattice model that
exhibits a quantum phase transition where both qubits and cavities
spontaneously polarise. We present a many-body ansatz that captures this
phenomenon all the way, from a the perturbative dispersive regime where photons
can be traced out, to the non-perturbative ultra-strong coupling regime where
photons must be treated on the same footing as qubits. Our ansatz also
reproduces the low-energy excitations, which are described by hybridised
spin-photon quasiparticles, and can be probed spectroscopically from
transmission experiments in circuit-QED, as shown by simulating a possible
experiment by Matrix-Product-State methods.Comment: closer to published versio
Driven Spin-Boson Luttinger Liquids
We introduce a lattice model of interacting spins and bosons that leads to
Luttinger-liquid physics, and allows for quantitative tests of the theory of
bosonization by means of trapped-ion or superconducting-circuit experiments. By
using a variational bosonization ansatz, we calculate the power-law decay of
spin and boson correlation functions, and study their dependence on a single
tunable parameter, namely a bosonic driving. For small drivings,
Matrix-Product-States (MPS) numerical methods are shown to be efficient and
validate our ansatz. Conversely, even static MPS become inefficient for
large-driving regimes, such that the experiment can potentially outperform
classical numerics, achieving one of the goals of quantum simulations
Differential expression of three galaxin-related genes during settlement and metamorphosis in the scleractinian coral Acropora millepora
BACKGROUND: The coral skeleton consists of CaCO3 deposited upon an organic matrix primarily
as aragonite. Currently galaxin, from Galaxea fascicularis, is the only soluble protein component of
the organic matrix that has been characterized from a coral. Three genes related to galaxin were
identified in the coral Acropora millepora.
RESULTS: One of the Acropora genes (Amgalaxin) encodes a clear galaxin ortholog, while the others
(Amgalaxin-like 1 and Amgalaxin-like 2) encode larger and more divergent proteins. All three
proteins are predicted to be extracellular and share common structural features, most notably the
presence of repetitive motifs containing dicysteine residues. In situ hybridization reveals distinct,
but partially overlapping, spatial expression of the genes in patterns consistent with distinct roles
in calcification. Both of the Amgalaxin-like genes are expressed exclusively in the early stages of
calcification, while Amgalaxin continues to be expressed in the adult, consistent with the situation
in the coral Galaxea.
CONCLUSION: Comparisons with molluscs suggest functional convergence in the two groups; lustrin
A/pearlin proteins may be the mollusc counterparts of galaxin, whereas the galaxin-like proteins
combine characteristics of two distinct proteins involved in mollusc calcification. Database searches
indicate that, although sequences with high similarity to the galaxins are restricted to the
Scleractinia, more divergent members of this protein family are present in other cnidarians and
some other metazoans. We suggest that ancestral galaxins may have been secondarily recruited to
roles in calcification in the Triassic, when the Scleractinia first appeared. Understanding the
evolution of the broader galaxin family will require wider sampling and expression analysis in a
range of cnidarians and other animals
Photon-Assisted-Tunneling Toolbox for Quantum Simulations in Ion Traps
We describe a versatile toolbox for the quantum simulation of many-body
lattice models, capable of exploring the combined effects of background Abelian
and non-Abelian gauge fields, bond and site disorder, and strong on-site
interactions. We show how to control the quantum dynamics of particles trapped
in lattice potentials by the photon-assisted tunneling induced by periodic
drivings. This scheme is general enough to be applied to either bosons or
fermions with the additional advantage of being non-perturbative. It finds an
ideal application in microfabricated ion trap arrays, where the quantized
vibrational modes of the ions can be described by a quantum lattice model. We
present a detailed theoretical proposal for a quantum simulator in that
experimental setup, and show that it is possible to explore phases of matter
that range from the fractional quantum Hall effect, to exotic
strongly-correlated glasses, or flux-lattice models decorated with arbitrary
patterns of localized defects
The Bulletpen
For more than 50 years Colombia has been immersed in an endless war. In 2016, a peace treaty between FARC guerrilla and the government was underway. In the middle of the political debate, we needed the media, and the world to be on our side and start talking about the good things that would come with the peace. This challenge led to the creative outcome of McCann Colombia, the case “Bulletpen”
El BalĂgrafo
Por más de 50 años, Colombia se ha visto inmersa en una guerra interminable. Pero en el 2016, se estaba negociando un tratado de paz entre el grupo guerrillero FARC y el gobierno. En medio del debate polĂtico que esto implica, necesitábamos que los medios de comunicaciĂłn nos ayudarán a apoyar el tratado, contándole al mundo acerca de las cosas buenas que venĂan con un paĂs en paz. Este desafĂo llevĂł al resultado creativo de la agencia de publicidad McCann Colombia, el caso “El BalĂgrafo”
Synthetic Gauge Fields for Vibrational Excitations of Trapped ions
The vibrations of a collection of ions in a microtrap array can be described
in terms of hopping phonons. We show theoretically that the vibrational
couplings may be tailored by using a gradient of the microtrap frequencies,
together with a periodic driving of the trapping potential. These ingredients
allow us to induce effective gauge fields on the vibrational excitations, such
that phonons mimic the behavior of charged particles in a magnetic field. In
particular, microtrap arrays are ideally suited to realize the famous
Aharonov-Bohm effect, and observe the paradigmatic edge states typical from
quantum-Hall samples and topological insulators.Comment: replaced with published versio
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