Reducing the Runtime of Fault-Tolerant Quantum Simulations in Chemistry through Symmetry-Compressed Double Factorization.

Quantum phase estimation based on qubitization is the state-of-the-art fault-tolerant quantum algorithm for computing ground-state energies in chemical applications. In this context, the 1-norm of the Hamiltonian plays a fundamental role in determining the total number of required iterations and also the overall computational cost. In this work, we introduce the symmetry-compressed double factorization (SCDF) approach, which combines a CDF of the Hamiltonian with the symmetry shift technique, significantly reducing the 1-norm value. The effectiveness of this approach is demonstrated numerically by considering various benchmark systems, including the FeMoco molecule, cytochrome P450, and hydrogen chains of different sizes. To compare the efficiency of SCDF to other methods in absolute terms, we estimate Toffoli gate requirements, which dominate the execution time on fault-tolerant quantum computers. For the systems considered here, SCDF leads to a sizable reduction of the Toffoli gate count in comparison to other variants of DF or even tensor hypercontraction, which is usually regarded as the most efficient approach for qubitization.

Vortex ring beams in nonlinear P T-symmetric systems.

In this paper, we investigate a two-dimensional photonic array featuring a circular shape and an alternating gain and loss pattern. Our analysis revolves around determining the presence and resilience of optical ring modes with varying vorticity values. This investigation is conducted with respect to both the array's length and the strength of the non-Hermitian parameter. For larger values of the array's length, we observe a reduction in the stability domain as the non-Hermitian parameter increases. Interestingly, upon increasing the vorticity of the optical modes, full stability windows emerge for shorter lattice size regime.

Fundamental efficiency bound for quantum coherent energy transfer in nanophotonics.

We derive a unified quantum theory of coherent and incoherent energy transfer between two atoms (donor and acceptor) valid in arbitrary Markovian nanophotonic environments. Our theory predicts a fundamental bound η m a x =γ a γ d+γ a for energy transfer efficiency arising from the spontaneous emission rates γd and γa of the donor and acceptor. We propose the control of the acceptor spontaneous emission rate as a new design principle for enhancing energy transfer efficiency. We predict an experiment using mirrors to enhance the efficiency bound by exploiting the dipole orientations of the donor and acceptor. Of fundamental interest, we show that while quantum coherence implies the ultimate efficiency bound has been reached, reaching the ultimate efficiency does not require quantum coherence. Our work paves the way towards nanophotonic analogues of efficiency-enhancing environments known in quantum biological systems.

Quantum analog of the maximum power transfer theorem.

We discover the quantum analog of the well-known classical maximum power transfer theorem. Our theoretical framework considers the continuous steady-state problem of coherent energy transfer through an N-node bosonic network coupled to an external dissipative load. We present an exact solution for optimal power transfer in the form of the maximum power transfer theorem known in the design of electrical circuits. Furthermore, we introduce the concept of quantum impedance matching with Thevenin equivalent networks, which are shown to be exact analogs to their classical counterparts. Our results are applicable to both ordered and disordered quantum networks with graph-like structures ranging from nearest-neighbor to all-to-all connectivities. This work points towards universal design principles adapting ideas from the classical regime to the quantum domain for various quantum optical applications in energy-harvesting, wireless power transfer, and energy transduction.

Combined effects of emitter-emitter and emitter-plasmonic surface separations dictate photoluminescence enhancement in a plasmonic field.

The brightness of an emitter can be enhanced by metal-enhanced fluorescence, wherein the excitonic dipole couples with the electromagnetic field of the surface plasmon. Herein, we experimentally map the landscape of photoluminescence enhancement (EFexp) of emitters in a plasmonic field as a function of the emitter-emitter separation, s, and the emitter-plasmon distance, t. We use Au nanoparticles overcoated with inert spacers as plasmonic systems and CdSe/ZnS quantum dots (QDs) as an emitter bearing opposite surface charges. The t and s are varied by changing the spacer thickness and number density of QDs on the plasmonic surface, respectively. The electrostatic binding of emitters on the plasmonic surface and their number density are established by following the variation of zeta-potential. EFexp is high, when t is short and s is large; nevertheless, it decreases when the emitter-emitter interaction dominates due to plasmon assisted nonradiative processes. In the absence of a plasmonic field, the enhancement observed is attributed to environmental effects and is independent of s, confirming the role of the electric field. Indeed, the distance dependence of EFexp closely follows the decay of the plasmonic field upon dilution of the emitter concentration on nanoparticles' surface (s = 18 nm). The QD-plasmon system is visualized in the framework of the Thomson problem, and classical electrodynamics calculations give the trends in t and s dependence of the photoluminescence. Being the first report on the simultaneous dependence of t and s on plasmon-enhanced photoluminescence, the results presented herein will open newer opportunities in the design of hybrid systems with a high brightness.

Long-Range Dipole-Dipole Interactions in a Plasmonic Lattice.

Spontaneous emission of quantum emitters can be enhanced by increasing the local density of optical states, whereas engineering dipole-dipole interactions requires modifying the two-point spectral density function. Here, we experimentally demonstrate long-range dipole-dipole interactions (DDIs) mediated by surface lattice resonances in a plasmonic nanoparticle lattice. Using angle-resolved spectral measurements and fluorescence lifetime studies, we show that unique nanophotonic modes mediate long-range DDI between donor and acceptor molecules. We observe significant and persistent DDI strengths for a range of densities that map to ∼800 nm mean nearest-neighbor separation distance between donor and acceptor dipoles, a factor of ∼100 larger than free space. Our results pave the way to engineer and control long-range DDIs between an ensemble of emitters at room temperature.

Microgenetic Analysis of Thought Trajectories: A Mixed Design.

This article reports the results of an investigation that used a mixed methodology with microgenetic orientation, to observe the genetic development of small acts of thought and their bodily manifestations. A qualitative design was carried out through a videographic record with 10 participants to explore thought trajectories and their genetic unfolding in gestures. In a second moment, a quantitative sequential analysis was conducted with 50 participants, who were invited to the laboratory to participate in a tachistoscopic presentation. The procedure was videotaped and coded, identifying categories of thought and their respective gestural expressions. An analysis of different trajectories was carried out to observe the transitions that thought takes and its gestural movements. The results show trajectories in the forms of thought that are investigated through a qualitative microgenetic analysis, which shows the anticipation of verbal meaning through gestures and the transitions backwards to then advance into more integrated forms of thought. On the other hand, trajectories between voluntary and involuntary forms of thought, as well as transitions in verbal and imaginative forms of thought are detected in a quantitative sequence analysis. Finally, the results are integrated and the utility of mixed designs to study the microgenesis of the consciousness phenomenon is discussed.

Relationship between self-care activities, stress and well-being during COVID-19 lockdown: a cross-cultural mediation model.

OBJECTIVES: To examine the mediation role of self-care between stress and psychological well-being in the general population of four countries and to assess the impact of sociodemographic variables on this relationship. DESIGN: Cross-sectional, online survey. PARTICIPANTS: A stratified sample of confined general population (N=1082) from four Ibero-American countries-Chile (n=261), Colombia (n=268), Ecuador (n=282) and Spain (n=271)-balanced by age and gender. PRIMARY OUTCOMES MEASURES: Sociodemographic information (age, gender, country, education and income level), information related to COVID-19 lockdown (number of days in quarantine, number of people with whom the individuals live, absence/presence of adults and minors in charge and attitude towards the search of information related to COVID-19), Perceived Stress Scale-10, Ryff's Psychological Well-Being Scale-29 and Self-Care Activities Screening Scale-14. RESULTS: Self-care partially mediates the relationship between stress and well-being during COVID-19 confinement in the general population in the total sample (F (3,1078)=370.01, p<0.001, R2=0.507) and in each country. On the other hand, among the evaluated sociodemographic variables, only age affects this relationship. CONCLUSION: The results have broad implications for public health, highlighting the importance of promoting people's active role in their own care and health behaviour to improve psychological well-being if stress management and social determinants of health are jointly addressed first. The present study provides the first transnational evidence from the earlier stages of the COVID-19 lockdown, showing that the higher perception of stress, the less self-care activities are adopted, and in turn the lower the beneficial effects on well-being.

Fractional discrete vortex solitons.

We examine the existence and stability of nonlinear discrete vortex solitons in a square lattice when the standard discrete Laplacian is replaced by a fractional version. This creates a new, to the best of our knowledge, effective site-energy term, and a coupling among sites, whose range depends on the value of the fractional exponent $\alpha$, becoming effectively long range at small $\alpha$ values. At long distance, it can be shown that this coupling decreases faster than exponentially: $\sim\exp (- |{\textbf{n}}|)/\sqrt {|n|}$. In general, we observe that the stability domain of the discrete vortex solitons is extended to lower power levels, as the $\alpha$ coefficient diminishes, independently of their topological charge and/or pattern distribution.

The impact of non-additive genetic associations on age-related complex diseases.

Genome-wide association studies (GWAS) are not fully comprehensive, as current strategies typically test only the additive model, exclude the X chromosome, and use only one reference panel for genotype imputation. We implement an extensive GWAS strategy, GUIDANCE, which improves genotype imputation by using multiple reference panels and includes the analysis of the X chromosome and non-additive models to test for association. We apply this methodology to 62,281 subjects across 22 age-related diseases and identify 94 genome-wide associated loci, including 26 previously unreported. Moreover, we observe that 27.7% of the 94 loci are missed if we use standard imputation strategies with a single reference panel, such as HRC, and only test the additive model. Among the new findings, we identify three novel low-frequency recessive variants with odds ratios larger than 4, which need at least a three-fold larger sample size to be detected under the additive model. This study highlights the benefits of applying innovative strategies to better uncover the genetic architecture of complex diseases.

Localized vortex beams in anisotropic Lieb lattices.

We address the issue of nonlinear modes in a two-dimensional waveguide array, spatially distributed in the Lieb lattice geometry, and modeled by a saturable nonlinear Schrödinger equation. In particular, we analyze the existence and stability of vortex-type solutions finding localized patterns with symmetric and asymmetric profiles, ranging from topological charge S=1 to S=3. By taking into account the presence of anisotropy, which is inherent to experimental realization of waveguide arrays, we identify different stability behaviors according to their topological charge. Our findings might give insight into experimental feasibility to observe these kinds of vortex states.

Strongly Coupled Exciton-Surface Lattice Resonances Engineer Long-Range Energy Propagation.

Achieving propagation lengths in hybrid plasmonic systems beyond typical values of tens of micrometers is important for quantum plasmonics applications. We report long-range optical energy propagation due to excitons in semiconductor quantum dots (SQDs) being strongly coupled to surface lattice resonance (SLRs) in silver nanoparticle arrays. Photoluminescence (PL) measurements provide evidence of an exciton-SLR (ESLR) mode extending at least 600 µm from the excitation region. We also observe additional energy propagation with range well beyond the ESLR mode and with dependency on the coupling strength, g, between SQDs and SLR. Cavity quantum electrodynamics calculations capture the nature of the PL spectra for consistent g values, while coupled dipole calculations show a SQD number-dependent electric field decay profile consistent with the experimental spatial PL profile. Our results suggest an exciting direction wherein SLRs mediate long-range interactions between SQDs, having possible applications in optoelectronics, sensing, and quantum information science.

Microscopic Theory of Plasmons in Substrate-Supported Borophene.

We compute the dielectric properties of freestanding and metal-supported borophene from first-principles time-dependent density functional theory. We find that both the low- and high-energy plasmons of borophene are fully quenched by the presence of a metallic substrate at borophene-metal distances smaller than ≃9 Å. Based on these findings, we derive an electrodynamic model of the interacting, momentum-dependent polarizability for a two-dimensional metal on a model metallic substrate, which quantitatively captures the evolution of the dielectric properties of borophene as a function of metal-borophene distance. Applying this model to a series of metallic substrates, we show that maximizing the plasmon energy detuning between borophene and substrate is the key material descriptor for plasmonic performance.

Non-Hermitian approach for quantum plasmonics.

We examine the limits of applicability of a simple non-Hermitian model for exciton/plasmon interactions in the presence of dissipation and dephasing. The model can be used as an alternative to the more complete Lindblad density matrix approach and is computationally and conceptually simpler. We find that optical spectra in the linear regime can be adequately described by this approach. The model can fail, however, under continuous optical driving in some circumstances. In the case of two quantum dots or excitons interacting with a plasmon, the model can also describe coherences and entanglement qualitatively when both dissipation and dephasing are present and quantitatively in the limit with no dephasing. The approach, within a single excitation manifold, is also applied to assess the role of disorder for 50 quantum dots interacting with a plasmon, where we find that, on average, large enough disorder can help stabilize the ensemble average of the open quantum system toward a dark quasi-steady-state much faster than without disorder. While such single excitation manifold calculations in this size limit can readily be done with either the non-Hermitian or Lindblad forms, as one goes to larger Hilbert space sizes, the computational and storage advantages of the non-Hermitian approach can become more useful.

Nonlinear optical lattices with a void impurity.

We examine a one-dimensional nonlinear (Kerr) waveguide array which contains a single "void" waveguide where the nonlinearity is identically zero. We uncover a family of nonlinear localized modes centered at or near the void, and their stability properties. Unlike a usual impurity problem, here the void acts like a repulsive impurity causing the center of the simplest mode to lie to the side of the void's position. We also compute the stability of extended nonlinear modes showing significant differences from the usual homogeneous nonlinear array. The transmission of a nonlinear pulse across the void shows three main regimes-transmission, reflection, and trapping at the void's position-and we identify a critical momentum for the pulse below (above) where the pulse gets reflected (transmitted), or trapped indefinitely at the void's position. For relatively wide pulses, we observe a steep increase from a regime of no transmission to a regime of high transmission, as the amplitude of the soliton increases beyond a critical wave-vector value. Finally, we consider the transmission of an extended nonlinear wave across the void impurity numerically, finding a rather complex structure of the transmission as a function of wave vector, with the creation of more and more transmission gaps as nonlinearity increases. The overall transmittance decreases and disappears eventually, where the boundaries separating passing from nonpassing regions are complex and fractal-like.

Spin photonics in 3D whispering gallery mode resonators.

Whispering gallery modes are known for possessing orbital angular momentum, however the interplay of local spin density, orbital angular momentum, and the near-field interaction with quantum emitters is far less explored. Here, we study the spin-orbit interaction of a circularly polarized dipole with the whispering gallery modes (WGMs) of a spherical resonator. Using an exact dyadic Green's function approach, we show that the near-field interaction between the photonic spin of a circularly polarized dipole and the local electromagnetic spin density of whispering gallery modes gives rise to unidirectional behaviour where modes with either positive or negative orbital angular momentum are excited. We show that this is a manifestation of spin-momentum locking with the whispering gallery modes of the spherical resonator. We also discuss requirements for possible experimental demonstrations using Zeeman transitions in cold atoms or quantum dots, and outline potential applications of these previously overlooked properties. Our work firmly establishes local spin density, momentum and decay as a universal right-handed electromagnetic triplet for near-field light-matter interaction.

Observation of long-range dipole-dipole interactions in hyperbolic metamaterials.

Dipole-dipole interactions (V dd) between closely spaced atoms and molecules are related to real photon and virtual photon exchange between them and decrease in the near field connected with the characteristic Coulombic dipole field law. The control and modification of this marked scaling with distance have become a long-standing theme in quantum engineering since dipole-dipole interactions govern Van der Waals forces, collective Lamb shifts, atom blockade effects, and Förster resonance energy transfer. We show that metamaterials can fundamentally modify these interactions despite large physical separation between interacting quantum emitters. We demonstrate a two orders of magnitude increase in the near-field resonant dipole-dipole interactions at intermediate field distances (10 times the near field) and observe the distance scaling law consistent with a super-Coulombic interaction theory curtailed only by absorption and finite size effects of the metamaterial constituents. We develop a first-principles numerical approach of many-body dipole-dipole interactions in metamaterials to confirm our theoretical predictions and experimental observations. In marked distinction to existing approaches of engineering radiative interactions, our work paves the way for controlling long-range dipole-dipole interactions using hyperbolic metamaterials and natural hyperbolic two-dimensional materials.

Fundamental figures of merit for engineering Förster resonance energy transfer.

Over the past 15 years there has been an ongoing debate regarding the influence of the photonic environment on Förster resonance energy transfer (FRET). Disparate results corresponding to enhancement, suppression and null effect of the photonic environment have led to a lack of consensus between the traditional theory of FRET and experiments. Here we show that the quantum electrodynamic theory (QED) of FRET near an engineered nanophotonic environment is exactly equivalent to an effective near-field model describing electrostatic dipole-dipole interactions. This leads to an intuitive and rigorously exact description of FRET, previously unavailable, bridging the gap between experimental observations and theoretical interpretations. Furthermore, we show that the widely used concept of Purcell factor variation is only important for understanding spontaneous emission and is an incorrect figure of merit (FOM) for analyzing FRET. To this end, we analyze the figures of merit which characterize FRET in a photonic environment 1) the FRET rate enhancement factor (FET), 2) FRET efficiency enhancement factor (Feff) and 3) Two-point spectral density (SEE) which is the photonic property of the environment governing FRET analogous to the local density of states that controls spontaneous emission. Counterintuitive to existing knowledge, we show that suppression of the Purcell factor is in fact necessary for enhancing the efficiency of the FRET process. We place fundamental bounds on the FRET figures of merit arising from material absorption in the photonic environment as well as key properties of emitters including intrinsic quantum efficiencies and orientational dependence. Finally, we use our approach to conclusively explain multiple recent experiments and predict regimes where the FRET rate is expected to be enhanced, suppressed or remain the same. Our work paves for a complete theory of FRET with predictive power for designing the ideal photonic environment to control FRET.

Variaciones en el número de metámeros del músculo recto abdominal. Una guía para la lipoescultura de alta definición / Variation in the number of metamers of rectus abdominis muscle. A high definition lipoesculture guide

Introducción y Objetivo. El recto abdominal es un músculo que consta, generalmente, de 3 inserciones tendinosas transversas. La lipoescultura de alta definición apunta a delinear la musculatura abdominal, sin embargo, una de sus dificultades es determinar mediante la anatomía de superficie el número de metámeros presentes. Nos planteamos describir las variaciones en el número de metámeros del músculo recto del abdomen en la población chilena mediante análisis de tomografía computarizada de abdomen y pelvis, así como determinar si existe un patrón para la marcación quirúrgica de los metámeros. Material y Métodos. Empleamos una muestra aleatoria de 200 pacientes que cumplían los criterios de inclusión: mayores de 18 años y menores de 65 años, estudio de tomografía computarizada de abdomen y pelvis con secuencia coronal realizado en el Hospital Clínico de la Universidad de Chile entre enero y mayo del 2017; y de exclusión: patología de la pared abdominal, cirugía abdominal previa, estudio imagenológico inadecuado. Describimos el sexo, número de inserciones tendinosas supra e infraumbilicales, ángulo costal corto, ángulo costal completo, diámetro xifo-umbilical y umbílico-púbico. Analizamos los datos con STATA® v13, considerando un valor estadísticamente significativo de p<0.05 e intervalos de confianza de 95%. Resultados. Del total de paciente, 100 (50%) de los pacientes fueron mujeres. La media de edad fue de 40,9 ± 12.1 años, y 154 pacientes (77%) tenían 3 metámeros. No evidenciamos diferencias significativas entre ambos sexos (p=0.393). Ni en el análisis de la distancia xifo-umbilical (p=0.185) ni de la umbílico-púbica (p=0.327) entre sexos respectivamente. El número de metámeros se encuentra en relación inversa al tamaño de los mismos. La angulación del reborde costal en relación al xifoides es significativamente menor en mujeres (69.4 ± 15.2 frente a 80.2 ± 14.2). Conclusiones. La anatomía más frecuente del músculo recto del abdomen en la población chilena corresponde a 3 metámeros supraumbilicales por cada recto abdominal. Cuanto menor sea la relación entre la distancia xifoumbilical / distancia xifo-púbica, menor cantidad de metámeros tiene el músculo recto. No fue posible predecir en forma precisa el número de metámeros mediante otra medida antropométrica

Background and Objective. Rectus abdominis muscle usually have 3 tendinous intersections. The aims of high definition abdominal liposculpture is to delineate the musculature. One of its difficulties is to determine by the surface anatomy the number of metamers presents. The aim of this study is to describe the variations in the number of metamers of the rectus abdominis muscle in the Chilean population and determine if there is a pattern that helps to the surgical mark of the abdominis metamers. Methods. Randomized sample of 200 patients who met inclusion criteria: >18 years of age and under 65 years, tomographic study of the abdomen and pelvis with coronal sequence, performed at the Clinical Hospital of the University of Chile between January and May 2017; and exclusion: pathology of the abdominal wall, previous abdominal surgery or inadequate imaging study. Sex, number of tendinous intersections supra and infraumbilical, short costal angle, complete costal angle, xipho-umbilical distance and umbilico-pubic measures were described. The data were analyzed with STATA®v13, being considered statistically significant with p<0.05 and 95% confidence intervals. Results. One hundred patients (50%) were women, mean age 40.9 ± 12.1 years, and 154 patients (77%) had 3 metamers. There were no significant differences by sex (p=0.393). Neither in the analysis of the xipho-umbilical distance (p=0.185) and the umbilical-pubic distance (p=0.327) by genders. The number of metamers is in inverse relation to its size. The angulation of the costal ridge relative to the xiphoid is significantly lower in women (69.4 ± 15.2 versus 80.2 ± 14.2). Conclusions. The most common rectus abdominis muscle pattern in the Chilean population corresponds to 3 supra umbilical metamers for each side (six-pack). The smaller the relationship between the xifo-umbilical distance / xifo-pubic distance, less number of metamers of the rectus abdominis. It was not possible to predict the number of metamers by another anthropometric measurement

Super-Coulombic atom-atom interactions in hyperbolic media.

Dipole-dipole interactions, which govern phenomena such as cooperative Lamb shifts, superradiant decay rates, Van der Waals forces and resonance energy transfer rates, are conventionally limited to the Coulombic near-field. Here we reveal a class of real-photon and virtual-photon long-range quantum electrodynamic interactions that have a singularity in media with hyperbolic dispersion. The singularity in the dipole-dipole coupling, referred to as a super-Coulombic interaction, is a result of an effective interaction distance that goes to zero in the ideal limit irrespective of the physical distance. We investigate the entire landscape of atom-atom interactions in hyperbolic media confirming the giant long-range enhancement. We also propose multiple experimental platforms to verify our predicted effect with phonon-polaritonic hexagonal boron nitride, plasmonic super-lattices and hyperbolic meta-surfaces as well. Our work paves the way for the control of cold atoms above hyperbolic meta-surfaces and the study of many-body physics with hyperbolic media.