403 research outputs found
Tunable and robust long-range coherent interactions between quantum emitters mediated by Weyl bound states
Long-range coherent interactions between quantum emitters are instrumental
for quantum information and simulation technologies, but they are generally
difficult to isolate from dissipation. Here, we show how such interactions can
be obtained in photonic Weyl environments due to the emergence of an exotic
bound state whose wavefunction displays power-law spatial confinement. Using an
exact formalism, we show how this bound state can mediate coherent transfer of
excitations between emitters, with virtually no dissipation and with a transfer
rate that follows the same scaling with distance as the bound state
wavefunction. In addition, we show that the topological nature of Weyl points
translates into two important features of the Weyl bound state, and
consequently of the interactions it mediates: first, its range can be tuned
without losing the power-law confinement, and, second, they are robust under
energy disorder of the bath. To our knowledge, this is the first proposal of a
photonic setup that combines simultaneously coherence, tunability, long-range,
and robustness to disorder. These findings could ultimately pave the way for
the design of more robust long-distance entanglement protocols or quantum
simulation implementations for studying long-range interacting systems
Generative adversarial networks for data-scarce spectral applications
Generative adversarial networks (GANs) are one of the most robust and
versatile techniques in the field of generative artificial intelligence. In
this work, we report on an application of GANs in the domain of synthetic
spectral data generation, offering a solution to the scarcity of data found in
various scientific contexts. We demonstrate the proposed approach by applying
it to an illustrative problem within the realm of near-field radiative heat
transfer involving a multilayered hyperbolic metamaterial. We find that a
successful generation of spectral data requires two modifications to
conventional GANs: (i) the introduction of Wasserstein GANs (WGANs) to avoid
mode collapse, and, (ii) the conditioning of WGANs to obtain accurate labels
for the generated data. We show that a simple feed-forward neural network
(FFNN), when augmented with data generated by a CWGAN, enhances significantly
its performance under conditions of limited data availability, demonstrating
the intrinsic value of CWGAN data augmentation beyond simply providing larger
datasets. In addition, we show that CWGANs can act as a surrogate model with
improved performance in the low-data regime with respect to simple FFNNs.
Overall, this work highlights the potential of generative machine learning
algorithms in scientific applications beyond image generation and optimization
Wave-front phase-modulation control and focusing of second-harmonic light generated in transparent nonlinear random structures
We theoretically investigate how phase-only spatial light modulation can enable controlling and focusing the second-harmonic light generated in transparent nonlinear random structures. The studied structures are composed of domains with random sizes and antiparallel polarization, which accurately model widely used ferroelectric crystals such as strontium barium niobate. Using a first-principles Green-function formalism, we account for the effect that spatial light modulation of the fundamental beam introduces into the second-order nonlinear frequency conversion occurring in the considered class of structures. This approach provides a complete description of the physical origin of the second-harmonic light generation in the system, as well as the optimization of the light intensity in any arbitrary direction. Our numerical results show how the second-harmonic light is influenced by both the disorder in the structure and the boundaries of the crystal. Particularly, we find that the net result from the interplay between disorder and boundary effects is strongly dependent on the dimensions of the crystal and the observation direction. Remarkably, our calculations also show that although in general the maximum possible enhancement of the second-order light is the same as the one corresponding to linear light scattering in turbid media, in the Cerenkov phase matching direction the enhancement can exceed the linear limit. The theoretical analysis presented in this work expands the current understanding of light control in complex media and could contribute to the development of a new class of imaging and focusing techniques based on nonlinear frequency mixing in random optical materials.Peer ReviewedPostprint (published version
Deep learning for the modeling and inverse design of radiative heat transfer
Deep learning is having a tremendous impact in many areas of computer science and engineering. Motivated by this success, deep neural networks are attracting increasing attention in many other disciplines,
including the physical sciences. In this work, we show that artificial neural networks can be successfully used in the theoretical modeling and analysis of a variety of radiative-heat-transfer phenomena and
devices. By using a set of custom-designed numerical methods able to efficiently generate the required
training data sets, we demonstrate this approach in the context of three very different problems, namely
(i) near-field radiative heat transfer between multilayer systems that form hyperbolic metamaterials,
(ii) passive radiate cooling in photonic crystal slab structures, and (iii) thermal emission of subwavelength objects. Despite their fundamental differences in nature, in all three cases we show that simple
neural-network architectures trained with data sets of moderate size can be used as fast and accurate
surrogates for doing numerical simulations, as well as engines for solving inverse design and optimization in the context of radiative heat transfer. Overall, our work shows that deep learning and artificial
neural networks provide a valuable and versatile toolkit for advancing the field of thermal radiatio
Tunable Thermal Emission of Subwavelength Silica Ribbons
The thermal properties of individual subwavelength
objects, which defy Planckâs law, are attracting significant
fundamental and applied interest in different research areas.
Special attention has been devoted to anisotropic structures made
of polar dielectrics featuring thicknesses smaller than both the
thermal wavelength and the skin depth. Recently, a novel
experimental technique has enabled the measurement of the
thermal emissivity of anisotropic SiO2 nanoribbons (with
thicknesses on the order of 100 nm), demonstrating that their
emission properties can be largely tuned by adjusting their
dimensions. However, despite the great interest aroused by these
results, their rigorous theoretical analysis has remained elusive due
to the computational challenges arising from the vast difference in
the length scales involved in the problem. In this work, we present a systematic theoretical analysis of the thermal emission
properties of these dielectric nanoribbons based on simulations within the framework of fluctuational electrodynamics carried out
with the boundary element method implemented in the SCUFF-EM code. In agreement with the experiments, we show that the
emissivity of these subwavelength structures can be largely tuned and enhanced over the thin-film limit. We elucidate that the
peculiar emissivity of these nanoribbons is due to the very anisotropic thermal emission that originates from the phonon polaritons
of this material and the properties of the waveguide modes sustained by these dielectric structures. Our work illustrates the rich
thermal properties of subwavelength objects, as well as the need for rigorous theoretical methods that are able to unveil the complex
thermal emission phenomena emerging in this class of systemsJ.J.G.E. was supported by the Spanish Ministry of Science and
Innovation through an FPU grant (FPU19/05281). J.B.A.
acknowledges financial support from the Ministerio de Ciencia,
InnovacionÌ y Universidades (RTI2018-098452-B-I00). J.C.C.
acknowledges funding from the Spanish Ministry of Science
and Innovation (PID2020-114880GB-I00
Weyl points in photonic-crystal superlattices
We show that Weyl points can be realized in all-dielectric superlattices based on three- dimensional (3D) layered photonic crystals. Our approach is based on creating an inversion- breaking array of weakly-coupled planar defects embedded in a periodic layered structure with a large omnidirectional photonic band gap. Using detailed band structure calculations and tight- binding theory arguments, we demonstrate that this class of layered systems can be tailored to display 3D linear point degeneracies between two photonic bands, without breaking time- reversal symmetry and using a configuration that is readily-accessible experimentally. These results open new prospects for the observation of Weyl points in the near-infrared and optical regimes and for the application of Weyl-physics in integrated photonic devices
Probing and harnessing photonic Fermi arc surface states using light-matter interactions
Fermi arcs, i.e., surface states connecting topologically distinct Weyl points, represent a paradigmatic manifestation of the topological aspects of Weyl physics. We investigate a light-matter interface based on the photonic counterpart of these states and prove that it can lead to phenomena with no analog in other setups. First, we show how to image the Fermi arcs by studying the spontaneous decay of one or many emitters coupled to the system's border. Second, we demonstrate that, exploiting the negative refraction of these modes, the Fermi arc surface states can act as a robust quantum link, enabling, e.g., the occurrence of perfect quantum state transfer between the considered emitters or the formation of highly entangled states. In addition to their fundamental interest, our findings evidence the potential offered by the photonic Fermi arc light-matter interfaces for the design of more robust quantum technologiesI.G.-E. acknowledges financial support from the Spanish Ministry for Science, Innovation, and Universities through FPU grant AP-2018-02748. A.G.-T. acknowledges financial support from the Proyecto SinĂ©rgico CAM 2020 Y2020/TCS-6545 (NanoQuCo-CM), from the CSIC Interdisciplinary Thematic Platform (PTI) Quantum Technologies (PTI-QTEP+), from Spanish project PID2021-127968NB-I00 and the project TED2021-130552B-C22 funded by MCIN/AEI/ 10.13039/ 501100011033/FEDER, UE, and MCIN/AEI/ 10.13039/501100011033, respectively, and the support from a 2022 Leonardo Grant for Researchers and Cultural Creators, BBVA. J.B.-A. and J.M. acknowledge financial support from the Spanish Ministry for Science, Innovation, and Universities through grants RTI2018-098452-B-I00 (MCIU/AEI/FEDER,UE) and MDM-2014-0377 (MarĂa de Maeztu programme for Units of Excellence in R&
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