IV School on Light and Cold Atoms

 

October 20 – 31, 2025

ICTP-SAIFR, São Paulo, Brazil

Venue: ICTP-SAIFR/IFT-UNESP
Zoom ID: 843 3376 6175
Password: cold

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Progress made during the past four decades in techniques for producing and controlling cold matter gave rise to the experimental manipulation of quantum gases, exotic states of matter, and the implementation of quantum simulators for condensed matter Hamiltonians. In addition, progress in the production and manipulation of quantum states of light and the suppression of classical noise allowed for the emergence and control of special coherence properties and quantum statistics, for both matter and light. These developments brought the fields of quantum optics and ultracold matter closer to applications, for example, in quantum sensing and quantum information processing. This common field of research represents today a privileged platform for fundamental discoveries of non-classical properties of light and matter, and an incubator of new quantum technologies.

This school aims at training PhD students, post-docs and outstanding master students in the physics of optics and cold atoms, introducing them to the basics, and familiarizing them with applications in modern technologies.

You can find information on the previous Schools on Light and Cold Atoms here:

School on Light and Cold Atoms 2023

School on Interaction of Light with Cold Atoms 2019

School on Interaction of Light with Cold Atoms 2017

 

This school will precede the School on Emergent Phenomena in Many-Body Systems.

 

Organizers:

  • Carla Hermann Avigliano (U. de Chile, Chile)
  • Mathilde Hugbart (Université Côte d’Azur, France)
  • Patrícia Christina Marques Castilho (IFSC-USP, Brazil)
  • Raul Celistrino Teixeira (UFSCAR, Brazil)
  • Romain Pierre Marcel Bachelard (UFSCAR, Brazil)

 

There is no registration fee and limited funds are available for travel and local expenses. It is highly recommended that participants in this event prepare poster presentations.

 

 

Announcement:

Application deadline: July 23, 2025 (closed)

Lecturers

Lecturers

  • Carla Hermann-Avigliano (University of Chile, Chile)

          Hands-on Scientific Communication: From Writing to Presenting Your Research

  • Daniel Felinto (UFPE, Brazil)

          Quantum networks with cold atoms

  • Hélène Perrin (Université Sorbonne Paris Nord, France)

          Two-dimensional Bose gases

  • Irina Novikova (College of William and Mary, USA)

          Atom-based quantum sensors: fundamentals and applications

          Atom-based quantum sensors: some like it hot (seminar)

  • Johannes Schachenmayer (Université de Strasbourg, France)

          Hands-on advanced numerical methods for quantum many-body dynamics

  • Michel Brune (ENS + Collège de France, France)

          From cavity QED to quantum simulations with circular Rydberg atoms

  • Stephen Walborn (Universidad de Concepción, Chile)

          Quantum information processing with photons

          Multicore optical fiber devices for quantum optics and information (seminar)

  • Thereza Paiva (UFRJ, Brazil)

          Optical lattices

Abstracts here.

Participants

Posters

    • Ardila, Juan (Universidad Nacional de Colombia, Colombia): Quantum Dynamics of a Pulsed Driven Bose Gas in an Optical Cavity

We investigate the quantum dynamics of a one-dimensional ultracold Bose gas in a harmonic trap, coupled to a coherently driven optical cavity. Using exact diagonalization, we compute the full many-body time evolution to characterize the system’s response to the driving pulse. Our analysis focuses on the interplay between intrinsic contact forces and cavity-mediated long-range interactions, examining the emergence of light-induced correlations, the excitation of collective modes, and the formation of hybridized atom-photon (polaritonic) states.

    • Attie, Jorge (São Carlos Institute of Physics – University of São Paulo, Brazil): Solitons in superfluids with curved geometries

The study of perturbations in superfluids, including Bose-Einstein condensates (BEC), is an interesting and active research area in modern nonlinear dynamics. One of these manifestations of perturbation is solitons, which consists of a pulse with finite and localized energy states, maintaining a constant shape and velocity for a long travel distance. The observation of such nonlinear objects was first documented by the scottish engineer John Scott Russell in 1834, under the therm “solitary wave”, depicting a water pulse in the canal between Edinburgh and Glasgow. Since then, solitons have been observed and studied in various platforms, such as optical fibers, waveguide, electric transmission lines, among other including bosonic atomic gases. In the case of bosonic gases, there remains an open window of investigation regarding gases in curved geometries, as their existence and stability in such contexts are not yet clear, making the research of solitons in curved settings a promissing and challenging area both theoretically and experimentally.

    • Ávila, Rafael Riveros (PUCV, Chile): Rabi-like oscillations in a quantum parametrically driven-dissipative dimer

Parametrically driven and dissipative quantum systems provide a rich platform for exploring nonlinear dynamics, quantum correlations, and phase transitions. This work studies the dynamics of a counter-phase driven-dissipative quantum dimer with Kerr nonlinearities and hopping interactions. We analyze the mean-field dynamics and stability of the system across different driving strengths (Ω) and coupling parameters (κ), identifying transitions between steady-state, oscillatory, and damped regimes. The oscillatory behavior resembles the traditional Rabi oscillations but in the presence of intrinsic dissipation, suggesting this toy model might lead to novel phenomena and applications in different fields. A dynamical systems analysis of the mean-field equations shows that the emergence of these oscillations is due to a global saddle-node bifurcation in the phase dynamics of the oscillators. In addition, ongoing work is focused on characterizing the effects of noise through a truncated Wigner function approach, leading to a Langevin-type equation for the system’s evolution.

    • Belumat, Gabriel Tardin (IFSC – USP, Brazil): Quantum vortices in the dimensional crossover 3D-2D

Quantum vortices, observed in different experimental platforms ranging from liquid helium to ultracold atomic gases are a hallmark of superfluidity and a key ingredient in explaining type-II superconductivity. In usual three-dimensional (3D) systems, these vortices are lines which interact and may bend, tangle and reconnect. Reducing the system’s dimensionality by compressing it in one direction of space, modifies the vortex geometry which can be modelled as a point-like object. Surprisingly point-like vortices and vortex-lines exhibit quite a different behaviour: while in 3D, vortex tangling leads to a turbulence state, in two dimensions (2D), point-like vortices tend to form clusters of same sign circulation giving rise to an effective negative temperature related to an inverse Komolgorov-like cascade of energy. In this project, we propose to follow the dynamics of deterministically created vortex arrays across the dimensional crossover 3D-2D in ultracold atomic systems. Within this approach, we expect to obtain clearer evidences of the particularities of the point vortex model, in particular, the dynamical formation of vortex clusters, and to explore the role of thermal fluctuations when deep in the 2D regime.

    • Brambila, Felipe Carvalho (Universidade Federal de São Carlos, Brazil): Limits of mean-field models for light propagation in material samples: the refractive index of a dense, cold atomic cloud

Considering the interaction between radiation and matter, refraction emerges as a particularly interesting phenomenon. Most optical materials exhibit a refractive index on the order of unity, whereas classical and semi-classical theories predict extremely high values. Following a recent theoretical proposal, cold atomic systems provide an ideal platform to investigate the upper limit of the refractive index observed in known materials. However, this saturation effect lacks experimental confirmation. The main goal of this project is to understand—through both experimental and theoretical work—how the refractive index of a cold atomic ensemble depends on matter density. The experimental group to which the student belongs has an apparatus capable of producing cold clouds of bosonic strontium, reaching densities sufficient to probe the predicted saturation of the refractive index. The project involves optimizing the atomic cooling process and implementing a system to measure the transmitted electric field through the sample. Due to the large parameter space, numerical simulations will also be employed to guide the search for the desired effects across different detunings and sample densities. What are the collective effects that saturate the refractive index around unity in most materials? How can we manipulate these effects to achieve a higher index? Answering these questions may lead to a better understanding of light transport in dense media and unlock new applications such as biological imaging, sub-diffraction imaging, and high-efficiency lenses.

    • Calazans De Brito, Luis Filipe (University of São Paulo, Brazil): Supersonic Flow Past an Obstacle in a Quasi-Two-Dimensional Lee–Huang–Yang Quantum Fluid

A supersonic flow past an obstacle can generate a rich variety of wave excitations. This paper investigates, both analytically and numerically, two types of excitations generated by the flow of a Lee–Huang–Yang quantum fluid past an obstacle: linear radiation and oblique dark solitons. We show that wave crests of linear radiation can be accurately described by the proper modification of the Kelvin original theory, while the oblique dark soliton solution is obtained analytically by transformation of the 1D soliton solution to the obstacle’s reference frame. A comparison between analytical predictions and numerical simulations demonstrates good agreement, validating our theoretical approach.

    • Camas Aquino, Fabian (Institurto de Física, UNAM, Mexico): On a theoretical study of the radiative transition probabilities of Hydrogen-like atoms illuminated by approximate spherical vector waves

We conducted a theoretical and numerical study of the transition probabilities of a hydrogen-like atom located around the focus of approximate spherical vector waves (ASVW). The coupling of light and matter in the non-relativistic approximation was used, while the illumination is generated in a 4π optical array consisting of two identical aplanatic lenses. The numerical results show the relevance of the numerical aperture of the lenses in the electric and magnetic multipolar radiation.

    • Cerda, Carlos Matias (Universidad de Chile, Chile): Towards Optimizing Intensity-Difference Squeezing in a Diode-Laser-Based Four-Wave Mixing Setup

We present ongoing work focused on characterising and optimising a system for generating intensity-difference squeezing (IDS) via four-wave mixing (4WM) in rubidium vapor. The setup uses a semiconductor diode laser to produce a strong pump beam (~795 nm, mW-level) and a weak seed beam (detuned by ~3 GHz, µW-level), which interact in a rubidium vapor cell heated to ~130 °C. The probe and conjugate beams generated through 4WM are detected, and their intensity difference is electronically measured to evaluate squeezing. Our goal is to identify the experimental conditions that maximise quantum noise reduction using diode-laser-based technology. Preliminary results show up to –4 dB of squeezing below the shot-noise limit at 1.5 MHz. This setup provides a testbed for exploring intense non-classical light generation and practical strategies for squeezing optimisation.

    • Coelho, Daniel Siqueira (Universidade Federal de São Carlos, Brazil): Diffusing Wave Spectroscopy in a Cold Atom Cloud

This project aims to apply the techniques of Diffusing Wave Spectroscopy (DWS) based on the coupled dipole model to understand the relevance of short-range terms (1/r² and 1/r³) in the dipolar interatomic interaction of light scattering. In this project, this phenomenon is studied through numerical simulations using MATLAB, starting from the creation of the cold atom cloud and analyzing the temporal autocorrelation function g¹(τ). The simulation will be performed with dependence on the parameters of optical depth (b0) and spatial density (ρλ³). This allows advances in understanding the phenomena associated with light scattering and may be applied in future experiments at the 88Sr laboratory. The results indicate that, in regimes of low optical depth and low spatial density, scattering is predominantly single, whereas for high densities and optical depths, collective effects become more significant. It also concludes that the DWS technique can provide valuable insights into light diffusion in a cloud of cold atoms, emphasizing the need for further studies to explore its effects in high spatial density and high optical depth regimes.

    • Da Costa, Alexandre Pereira (Universidade de Brasília – Programa de Pós graduação em Física, Brazil): Investigating quantum Fisher information in circuit QED

Improving the precision of parameter estimation in quantum systems is fundamental for quantum technologies. In this context, a key quantity is the quantum Fisher information (QFI), which sets the ultimate bound on precision estimation via the quantum Cramér-Rao inequality. Maximizing the QFI with respect to a given parameter identifies an optimal regime where the system reached the highest precision in parameter estimation. Therefore, in this work we investigate the QFI associated with the generation of photons from vacuum in circuit quantum electrodynamics (QED). Our results may provide an insight into how quantum systems in circuit QED can achieve peak precision in parameter estimation.

    • Da Silva, Welberth (Instituto de Física – Universidade Federal do Rio de Janeiro, Brazil): Extended Hubbard model on a honeycomb lattice.

The recent discovery of correlated insulating phases and superconductivity in magic-angle twisted bilayer graphene (TBG) has spawned renewed interest in the study of strongly correlated phenomena on a honeycomb lattice (HC). From a theoretical perspective, the Extended Hubbard Model (EHM) is one of the simplest models describing emergent magnetic, charge, and superconducting orders in electronic systems. Indeed, while a repulsive on-site interaction, $U > 0$, favors the formation of magnetic moments and their effective coupling, the presence of a repulsive nearest-neighbor interaction, $V > 0$, enhances charge correlations, thus favoring arrangements of doubly occupied sites. If one allows for attractive interactions in either the on-site or the nearest-neighbor channels, or both, one may wonder which pairing states may be stabilized in the ground state. With this in mind, here we use determinant quantum Monte Carlo simulations to probe the whole (i.e., the four possible combinations of $U$ and $V$ being positive or negative) phase diagram of the half-filled EHM on a HC lattice. The calculations have been carried out with complex Hubbard-Stratonovich (HS) auxiliary fields to yield sign-free simulations in the range $|V| \leq |U|/3$, in which case structure factors probing the ordered phases have been fed into correlation ratios; this allows for precise determination of critical boundaries through finitesize scaling analyses. Outside this region we use real HS fields and resort to additional local quantities, such as double occupancy and the average sign of the product of fermionic determinants, to determine the boundary of the CDW phase with a high degree of confidence. We have also established that only $s$-wave superconductivity is present, in marked contrast with the square lattice where $d$-wave pairs can be preferably stabilized. Further, as $|V|$ increases, the AFM phase demands larger values of U to stabilize. As expected, for sufficiently small $V < 0$, a phase separated region dominates the whole diagram for all $U$.

    • De Paula, Marcos (Universidade de Brasília, Brazil): Interaction of Light Matter from the Rabi Model Ressonance

The Rabi model, which phenomenologically describes a two-level atom interacting with a field, outlines the properties of energy transfer between its constituents, along with photon emission and absorption. The representation of this system can be approximated through various methods, including well-established approaches in the literature as well as innovative techniques developed in this study. The introduction of effective interactions proposed here is particularly relevant for specific frequency ranges near the values associated with photon generation and absorption by the system. The model is investigated both in the fully quantum and semiclassical limits, with the distinction based on the origin of the field. Additionally, we analyze the system using the coherent state associated with the field’s energy level. Finally, we compare the excited-state probabilities in both formalisms. In addition to characterizing the equations governing the system’s dynamics, this provides a deeper understanding of phenomena related to light-matter interaction.

    • Donda Acosta, Inara Yasmin (Instituto de Física de São Carlos, Brazil): Levitation system for ultracold atomic cloud of potassium-39

Ultra-cold gases are produced in highly isolated environments and manipulated using magnetic fields and laser beams. In this context, various types of traps are employed to create atomic clouds with distinct geometries and dimensions. Despite efforts to isolate the system from external perturbations, one unavoidable factor remains: the gravitational force exerted by the Earth. Methods for compensating this force, capable of levitating the atomic cloud, have been widely adopted in ultra-cold gas experiments. They are particularly crucial in setups involving vertical imaging (as in the experiment related to this project), where the free fall of the cloud leads to image de-focusing. In this project, we propose the development of a magnetic levitation system to be implemented in a new experimental setup under construction at IFSC, which aims to produce two-dimensional Bose gases. This system is essential for improving imaging quality and ensuring precise control of the atomic cloud’s position during the experiment.

    • Dos Santos Ferreira, Joao Vitor (UFSCar, Brazil): Signatures of Anderson localization of light in 2D disordered systems

Anderson localization has been evidenced for waves from 1D to 3D systems, from acoustic to matter waves. However, light waves were shown to exhibit near-field terms which prevent localization in 2D and 3D [1, 2]. With several experimental results reinterpreted, a major challenge for the observation of the localization transition for lightis the identification of unambiguous signatures. In this context, two-dimensional samples are particularly interesting, because they possess both scalar (without near-field terms and with localization) and vectorial (with near-field and without localization) scattering channels. In this work we discuss which observables in the scattered light can be used as signatures of Anderson localization, exploiting the transmission profile of the intensity [3, 4] characterized by the phenomenon of ”transverse localization”, and the deviations from Ohm’s law for diffusion [5]. More precisely, we show how the spatial evolution of the beam width [4] and the decay of the transmission coefficient [6] differ in the scalar and vectorial channels, witnessing the different regimes explored. Indeed, while the diffusion, in the vectorial channel, is a scale-free process, in the scalar channel localization sets a characteristic spatial scale for the scattered light in space – yet another way to access the localization length [7]. Through a spatial analysis of the diffusion coefficient, it was shown that the localization length obtained by macroscopic observables is in agreement with the self-consistent theory, even at high disorder [8]. [1] S. E. Skipetrov and I. M. Sokolov, “Absence of anderson localization of light in a random ensemble of point scatterers,” Physical review letters, vol. 112, no. 2, p. 023905, 2014. [2] C. E. M´aximo, N. Piovella, P. W. Courteille, R. Kaiser, and R. Bachelard, “Spatial and temporal localization of light in two dimensions,” Physical Review A, vol. 92, no. 6, p. 062702, 2015. [3] H. De Raedt, A. Lagendijk, and P. de Vries, “Transverse localization of light,” Physical review letters, vol. 62, no. 1, p. 47, 1989. [4] N. Cherroret, S. Skipetrov, and B. Van Tiggelen, “Transverse confinement of waves in three-dimensional random media,” Physical Review E, vol. 82, no. 5, p. 056603, 2010. [5] F. Cottier, A. Cipris, R. Bachelard, and R. Kaiser, “Microscopic and macroscopic signatures of 3d anderson localization of light,” Physical review letters, vol. 123, no. 8, p. 083401, 2019. [6] L. Schertel, O. Irtenkauf, C. M. Aegerter, G. Maret, and G. J. Aubry, “Magnetic-field effects on one-dimensional anderson localization of light,” Physical Review A, vol. 100, no. 4, p. 043818, 2019. [7] J. V. Ferreira, N. Araujo, R. Kaiser, and R. Bachelard, “Two-dimensional transverse localization of light,” in preparation. [8] A. M. G. De Melo, ´ Laser cooling of Yb on the intercombination line for experiments on localization of light. PhD thesis, Universit´e Cˆote d’Azur, 2024.

    • Dos Santos Silva, Gustavo Henrique (Univiversidade de São Paulo, Brazil): Vortex generation through the passage of an obstacle and determination of the critical velocity in a condensate beyond the mean-field approximation, including LHY corrections

In this work, we investigate the dynamics of a Gaussian obstacle moving through a quantum fluid, known as the LHY fluid. We observed vortex production for velocities above $v_c$, consistent with the behavior expected in the mean-field regime. We also analyzed the drag force on the obstacle and concluded that, for velocities below the critical value, the drag is zero, indicating that the obstacle flows with minimal resistance. Above the critical velocity, the drag becomes periodic, with peaks corresponding to vortex emissions. Finally, we determined the critical velocity by analyzing the point where the average drag ceases to be zero, identifying this value as the critical velocity.

    • Farias Vasconcelos, Joao Lucas (Instituto de Física de São Carlos, Brazil): Effects of Low Dimensionality and Curvature on Superfluid Mixtures

Given the new techniques for the experimental production of ultracold gas mixtures consisting of fermionic and bosonic dipolar components, in a variety of confinement geometries, in this work we will explore the quantum phases of a system composed of a two-dimensional degenerate dipolar Fermi gas. We will consider corrections beyond the mean-field approximation in order to better characterize the system’s phases, which will be subject to a bath composed of a three-dimensional condensed bosonic gas. In addition to the effects of the interaction mediated by the bath, we will also analyze the potential of the dipolar interaction between the fermions in different confinement geometries: a single plane, two planes with variable distance, and a spherical film. Our results will be fundamental for shedding light on an area that is still scarcely explored from a theoretical perspective, but whose experimental techniques already allow the implementation and analysis of the system proposed in this project.

    • Follador, Lorenzo (USP, Brazil): Entanglement Between Transverse Modes of an Optical Parametric Oscillator

To Be Determined

    • Forlevesi, Murilo Deliberali (Sao Paulo State Universty – Unesp, Rio Claro, Brazil, Brazil): Formation of oriented polar molecules with a single shaped pulse

Combining the purposes of formation and orientation, this study aims to understand the capacity of the fields in this dual objective control opening the possibility for new experiments. We investigate the coherent formation of oriented heteronuclear diatomic molecules via single-channel infrared photoassociation. The process is driven by a time-dependent, linearly polarized control field and proceeds entirely within a single electronic ground state, leveraging the presence of a permanent dipole moment. The control objective is to simultaneously maximize molecular bond formation and spatial orientation along the laboratory-fixed polarization axis.

    • Fuentes Jara, Florencia Andrea (Universidad de Concepción, Chile): In-House Development of an Optically Feedback-Stabilized Diode Laser for Atomic Spectroscopy in Resource-Constrained Environments

This work presents a cost-effective diode laser system for high-resolution atomic spectroscopy, which was designed and constructed at Universidad de Concepción’s LAMP laboratory utilizing only commercial components. The laser utilizes a Littrow-configuration external cavity with a diffraction grating and piezoelectric transducer for coarse/fine wavelength tuning. Optical feedback stabilization and feedback loop reduces the line width to sub-MHz levels that is essential for addressing atomic transitions in rubidium. This system performs at a level comparable to commercial scientific lasers for a much better part of the price, facilitating accurate spectroscopy in our ongoing cold atoms research. The method illustrates how resource-constrained labs can develop atomic and quantum optics capability through modular, in-house solutions.

    • García Zurita, Arturo (Centro de Investigación Científica y de Educación Superior de Ensenada, Baja California, México, Mexico): Spectral translation of photonic states by difference frequency generation process.

In response to the growing demand for emerging technologies such as quantum computing, non-classical light states have established themselves as a key resource for advanced information processing. In this context, the spectral manipulation of photonic states by nonlinear optical processes acquires strategic importance. This work presents the experimental implementation of the spectral translation of an optical field based on the third-order nonlinear process known as difference frequency generation (DFG). This phenomenon allows the coherent conversion of the frequency of a photon, preserving the quantum properties of the initial state, and is essential for tasks such as the interconnection of quantum platforms or the manipulation of colored cubits. The experimental design consists of two main stages. In the first, correlated photon pairs are generated by spontaneous four-wave mixing (SFWM) in a birefringent Bow-Tie optical fiber. Subsequently, one of the photons is introduced into a photonic crystal fiber (PCF), where its spectral translation is induced via the DFG process, in the presence of a second continuous pumping. To ensure the efficiency of the process, simulations of the phase matching were carried out for both nonlinear processes, as well as of the expected spectral properties of the states involved. These simulations allowed us to optimize the experimental parameters and validate the results obtained. By means of spectrally resolved photon counting, the spectra of the input state and the translated state were measured. The results show a coherent signal in the expected band, which experimentally confirms the spectral translation under the proposed conditions. This advance represents an important step towards the implementation of spectral conversion-based quantum gates and the integration of quantum photonic networks.

    • Ghosh, Avisikta (BITS Pilani K. K. Birla Goa Campus, India): Non-Classical Light and Cold Atom Magnetometry

Cold atom magnetometry offers a platform for increased sensitivity by manipulating the quantum properties of atoms. In this work, we will aim to explore how non-classical states of light-such as squeezed light can be used to surpass the Standard Quantum Limit (SQL) and approach the Heisenberg limit through methods like Faraday rotation, Quantum Non-Demolition (QND) measurements and spin squeezing generation. We will present theoretical insights into how the use of non-classical light enhances signal-to-noise ratios, pushing sensitivity beyond SQL. This approach holds significant promise for advanced quantum metrology requiring high-precision magnetometry.

    • Granados Umanzor, Napoleón Enrique (Centro de Investigación Científica y de Educación Superior de Ensenada, Baja California, México, Mexico): Generation and manipulation of multiphoton states in solid-state emitters coupled to integrated photonic circuits

Multiphoton states are quantum states of light that involve multiple photons, either in a well-defined number or following a statistical distribution. They are useful in applications such as quantum computing, metrology, and communication. These states are typically generated through nonlinear optical processes, such as spontaneous parametric down-conversion and spontaneous four-wave mixing. However, this research explores the possibility of generating them in solid-state sources, such as nitrogen-vacancy centers in diamond and defects in hexagonal boron nitride, assessing their feasibility by measuring the second-order correlation function g(2)(t), and leveraging the use of superconducting nanowire single-photon detectors with photon-number resolution. The main objective is to study the integration of these emitters with photonic circuits for the generation, control, and characterization of multiphoton states, aiming to develop a scalable platform for quantum technologies. Integration into photonic circuits is essential to improve the stability and efficiency of photon manipulation, facilitating the practical implementation of quantum networks and advanced optical computing.

    • Gutierrez Gomez, Cristian Leonardo (Universidad Pedagogica y Tecnologica de Colombia, Colombia): Wannier equation for excitons with the Rytova–Keldysh potential in 2D semiconductors

The understanding exciton (electron-hole pair) dynamics is of great importance for the advancement of emerging quantum technologies. In particular, the study of exciton properties in two-dimensional (2D) transition metal dichalcogenides (TMDs) is especially relevant due to their potential applications, such as sources of single-photon emitters. These sources are strong candidates for use in quantum information processing and quantum computation. In this work, we present a detailed analysis of the exciton structure using the Wannier equation, which is a simplified form of the Bethe–Salpeter equation in 2D. These are integral equations that, for realistic interaction potentials, must be solved numerically. The Wannier equation is a homogeneous Fredholm integral equation in 2D. In this contribution, we present an efficient numerical method to solve it, based on partial-wave decomposition and Gauss–Legendre quadrature. This approach reduces the problem to a one-dimensional integral equation, which is significantly easier to handle computationally. For the electron-hole interaction, we employ the well-known Rytova–Keldysh potential. As a result, we obtain the exciton energies and corresponding wave functions in momentum space. Finally, as a direct application, we show how the exciton wave function can be used to quantitatively describe exciton–phonon coupling in 2D semiconductors.

    • Jaramillo Quenguan, Miguel Angel (Universidad del valle, Colombia): Coherent Raman spectroscopy using interference of entangled photon pairs

In the context of quantum sensing and quantum light spectroscopy, this thesis proposes a new approach to Raman spectroscopy using interference from entangled photon pairs. The proposal is inspired by the technique of femtosecond quantum Raman spectroscopy (QFRS) and proposes a variant based on induced quantum coherence, with the aim of reducing susceptibility to noise in measurements. To support the viability of this approach, previously established analytical models will be reviewed and models will be developed to serve as a basis for the implementation of numerical simulations. This approach aims to contribute to the consolidation of advanced quantum light spectroscopy schemes, with potential applications in technologies such as quantum LiDAR.

    • Lemus Saldivar, Juan Pablo (Instituto de Física / Universidad Nacional Autónoma de México, Mexico): Working with a multicomponent ultracold Fermi gas

At the Ultracold Matter Laboratory (LMU), we study degenerate Fermi gases of $^6$Li at temperatures below the microkelvin range. The initial two-component system comprises atoms in the two lowest hyperfine states, $\ket{F=1/2,m_F=-1/2}\equiv\ket{1}$ and $\ket{F=1/2,m_F=+1/2}\equiv\ket{2}$, magnetically separated by the Zeeman effect. Operating within a magnetic field range of $65-90$ mT allows precise manipulation of interactions via Feshbach resonances. We generate a third state, $\ket{F=3/2,m_F=-3/2}\equiv\ket{3}$, by applying radiofrequency (RF) radiation, thereby creating a multicomponent Fermi gas. Crucially, the Feshbach resonances for all three pairwise interactions lie close together within this operational magnetic field range, enabling rich many-body physics. Our work explores the population constitution of this third state, investigating the transition from an impurity regime to a balanced tripartite system.

    • Lima, Caio César Rocha (IFSC, Brazil): Magneto-optical trapping of Dysprosium in alternative configuration

Magneto-optical traps are among the main tools in Atomic and Molecular Physics, making use of the radiation pressure force to confine and cool atoms of various species. Recently, it has been demonstrated that magneto-optical traps operating on narrow-linewidth transitions can be implemented without the beam aligned along the direction of gravity. These are known as five-beam traps, in contrast to the traditional six-beam configuration of conventional magneto- optical traps. Such trapping is only possible because the radiation pressure force in narrow- line transitions is comparable to the gravitational force. In this doctoral project, we aim to advance in this direction by proposing magneto-optical traps based on four-beam and three- beam configurations for Dysprosium atoms. The present project will develop all the necessary steps for achieving trapping, from the establishment of the atomic source, through the laser systems, to the trapping itself and the characterization of the trap.

    • Macêdo, Thales Freitas (Instituto de Física UFRJ, Brazil): Estimation of the electron-photon coupling in optical cavities

In this work, we address the inverse problem of estimating the electron–photon coupling strength from electronic transport measurements. Specifically, we propose a theoretical framework in which the cavity-modified conductance of a correlated electronic system is used as an indirect probe of the coupling intensity. Our approach provides a route to experimentally accessible estimates of light–matter coupling.

    • Mitchell Galvão De Melo, Álvaro (University of Basel, Switzerland): Atom-Optomechanical coupling in the quantum regime

We engineer light-mediated Hamiltonian interactions between a mechanical oscillator and an atomic spin system separated by one meter, using a looped geometry [Science 369, 174-179 (2020)]. These interactions enable coherent feedback cooling of the mechanical oscillator by employing the atomic spin as a controller [PRX 12, 011020 (2022)]. When the two systems are coupled, noise from the oscillator can be transferred to the spin, which has a broader linewidth than the mechanical oscillator. As the excitations are transferred back, the phonon number of the oscillator is effectively reduced, resulting in cooling. In this presentation, we will discuss the current progress and future directions of the experiment, including the realization of coupling in the quantum-noise-limited regime—where the light–system coupling rate exceeds the decoherence rate—and prospects for achieving ground-state cooling of a cryogenically pre-cooled mechanical oscillator.

    • Mondaca, Jose Ignacio (Universidad de Chile, Chile): Entanglement in a System of Three Coupled Quantum dots

Entanglement is one of the main resources of quantum information processing and a fundamental property of quantum mechanics. It plays a crucial role in quantum key distribution, quantum computing, metrology and quantum thermodynamics. The development of quantum technologies has led to significant experimental advances, including the study of nanoelectronic devices known as quantum dots. These systems have been widely used in quantum thermodynamics research, particularly in the study of transport effects. [1] In our research, we describe the dynamics of a system of three quantum dots coupled via hopping and Coulomb interactions, analyzing fully quantum effects such as entanglement in the transport of electrons. To preserve quantum features like coherence and entanglement, we employ a recently developed approach by Potts [2] called the semilocal approximation. Unlike the secular Lindblad equation, this method retains coherences even in the steady state while remaining thermodynamic consistent. [1] Kacper Prech and Philip Johansson and Elias Nyholm and Gabriel T. Landi and Claudio Verdozzi and Peter Samuelsson and Patrick P Potts, Phys. Rev. Res. 5, 023155 (2023). [2] Patrick P Potts, Alex Arash Sand Kalaee y Andreas Wacker, New J. Phys. 23 123013 (2021)

    • Montenegro, Lukas (Institute of Physics, USP, Brazil): Spatial-temporal control of the SPDC’s two-dimensional biphoton joint spectral function

Spontaneous parametric down-conversion (SPDC) is an important phenomenon that provides quantum communications protocols with both high-fidelity entangled pairs of photons and highly pure single photon states. The properties of the photons generated through this process depend on the nature of their joint spectral function (JSA), which can be tailored by modifying both the spectral profile of the pumping field and the phase-match function between the pump and signal/idler fields. While the first is simple to perform with wave shapers and electro-optical modulators, the second is often complicated, since it involves finely engineering the susceptibility of the SPDC crystal. In this work we propose to use only a spatiotemporal structured pump light to achieve a considerable level of control over the JSA. We deeply explore the role of the Gouy phase on the correlations and SPDC and possible limitations. In practice, the center of the protocol involves the use of an optimization algorithm to properly program a spatial light modulator (SLM), making our approach more accessible to ordinary quantum optics laboratories.

    • Morais, Iago Ferreira (São Carlos Institute of Physics, Brazil): Development of an Ion Trap for Quantum Computing and Precision Measurements: Stabilizing Lasers to Ultra-Stable References.

Recent advances in quantum technologies highlight the central role of lasers in experiments with neutral atoms, trapped ions, and molecules, whether for cooling or for controlling quantum states. To achieve reproducibility and enable high-precision studies, these lasers must be frequency- and power-stabilized. For narrow atomic transitions relevant to quantum computing and quantum memories, ultra-stable frequency locking using high-finesse Fabry–Pérot cavities becomes indispensable. In this project, we aim to stabilize a laser to an ultra-stable high-finesse cavity that serves as a reference for locking an optical frequency comb. This setup transfers the stability of the main laser to multiple wavelengths, in particular 674 nm, crucial for implementing optical qubits in trapped Sr⁺ ion experiments, enabling scalable quantum technologies and precision metrology. Key words: Ion Trap, Precision Metrology, Qubits, Frequency Locking and Optical Frequency Comb.

    • Moya, Amaru Gael (Universidad de Concepción, Chile): Enhancing Single Photon Sources Through Collective Atomic Behaviours

(Preliminary abstract – subject to updates) The generation of reliable single photons is essential for quantum communication and optical quantum information processing. Among the most studied, the DLCZ protocol shines as one of the most popular, using atomic ensembles to produce heralded single photons through through a Raman process. In this work, we investigate the controlled generation of deterministic single photons—anti-Stokes photons—based on the DLCZ protocol in a cold Rubidium cloud. Our approach involves comparing a standard Gaussian-mode implementation of the DLCZ scheme with a configuration that incorporates superradiant emission. By analyzing and contrasting both schemes, we aim to understand how collective behaviors in atomic ensembles can improve the performance and efficiency of single-photon sources.

    • Muñoz Fuentealba, Camila Francisca (Universidad de Concepción, Chile): A Graph-Based Framework for the Decay Rate of Connected Superatoms in Waveguide QED

An ensemble of atoms coupled to a single-mode waveguide can behave as a single collective emitter—a superatom—with enhanced decay into the guided mode. In this work, we propose a theoretical framework to describe the collective decay properties of multiple superatoms connected via generalized 2N-port beam splitters. We show that such a configuration can act effectively as a multidimensional superatom, where the spatially distributed ports represent different directions of coupling within an extended collective emitter. The interaction structure of this network is captured by a decay matrix whose form corresponds to the adjacency matrix of an effective graph. This mapping allows us to apply graph-theoretic tools to compute the collective decay spectrum of the system. In particular, we derive a general expression for the maximum superradiant decay rate in arbitrary D-dimensional lattice configurations. Our results provide a compact and scalable approach to model structured light–matter interactions in waveguide QED, and offer a route toward engineered quantum optical networks based on collective emission.

    • Noguera Velasco, Ana Carolina (Universidad del Valle, Colombia): Cold atom-atom-ion three-body recombination assisted by radiofrequency trap

Cold hybrid atom-ion systems offer a unique platform to explore charge-neutral interactions with high precision and to investigate the behavior of a charged impurity embedded in a quantum-degenerate atomic gas. Achieving the fully quantum s-wave regime in such systems remains a significant challenge, requiring a deep understanding of—and control over—various loss mechanisms. Recent studies have shown that cold atom–atom–ion collisions in the presence of a radiofrequency field can exhibit vibrational resonances with lifetimes on the order of nanoseconds. During this brief window, the resulting dimer can interact with a third atom, leading to three-body recombination. In this process, the third atom carries away excess energy, stabilizing the dimer into a bound diatomic molecule, which is subsequently lost from the trap. To investigate this loss channel, we have developed a semiclassical molecular dynamics simulation to model the formation of such molecules. We compute three-body recombination rates and analyze how various system parameters influence the complex formation. These insights can help develop strategies to mitigate atom-ion losses in cold hybrid systems.

    • Orellana, Enrique Flavio (University of Concepción, Chile): Generation of Magnetic Fields in the Absence of Electric Fields Using Laguerre-Gauss Beams

Laguerre-Gauss (LG) beams are notable for their ability to carry orbital angular momentum, characterized by the azimuthal index l. This parameter plays a key role in the beam’s structure, as it determines the emergence of optical vortices and the distribution of electromagnetic energy. As |l| increases, the beam acquires a more complex helical structure, which significantly alters the spatial distribution of the electric and magnetic fields. A particularly striking feature is that for |l| > 0, the electric field vanishes along the beam axis. In contrast, the magnetic field can remain non-zero, although its intensity and distribution are also influenced by the value of l. For the case |l| = 2, it is possible to obtain a non-zero magnetic energy density at the beam center, while the electric energy vanishes locally. This type of configuration is studied through the full electromagnetic field equations for LG beams, with the goal of identifying conditions that maximize the axial magnetic field in the absence of an electric field. Such a property is especially relevant for applications requiring selective interaction with magnetic moments of particles or atoms—such as the design of highly selective optical traps, electric-field-free spectroscopy techniques, and the coherent manipulation of cold atoms without disturbing their electric states. Generating magnetic fields using light, isolated from electric field components, enables the exploration of new regimes of quantum control and opens experimental pathways that minimize perturbative effects of electric fields on sensitive quantum systems. [1] L. Allen et al. Orbital angular momentum of light and the transformation of Laguerre-Gaussian laser modes, Phys. Rev. A 45, 8185 (1992) [2] V. Klimov, D. Bloch, M. Ducloy Detecting photons in the dark region of Laguerre-Gauss beams, Opt. Express 17, 9718-9723 (2009) [3] V. Klimov, D. Bloch and M. Ducloy, Mapping of focused Laguerre-Gauss beams: The interplay between spin and orbital angular momentum and its dependence on detector characteristics, Physical Review 85, 053834 (2012)

    • Oryan, Gabriel (Facultad de ciencias físicas, Universidad de Concepción., Chile): Fabrication of silica nanofiber for cold atoms experiments

In this poster I will talk about the process needed to create tapered silica nanofiber that work for cold atoms in an Magneto optical trap. I will talk about the mechanical and thermal consideration when making the nanofiber and how to track the process in order to achieve 99% transmission for the single-mode. I will show how to trap atoms using the light and how light changes by interacting with the atoms.

    • Pereira, Thales (Universidade de São Paulo, Brazil): Coherent and incoherent transmission of a dense atomic sample in the linear and saturated regimes

This project aims to study the scattering of light by a dense sample of cold strontium atoms. Specifically, this project aims to implement a measurement of the electric field of light transmitted through a dense and disordered atomic sample. The measurement of the electric field will extend the regime of parameters for which we can characterize the true optical density of the cloud, in relation to the possibilities established by the measurement of the intensity of the transmitted light. Furthermore, the phase of the electric field will allow us to obtain the refractive index of the dense sample, of high fundamental interest. To do this, the student will initially optimize the cloud’s cooling parameters, so that it is suitable for the experimental objectives of this project. For that, it’s necessary to establish, theoretically, the different noise sources expected for the system, thus determining the expected signal-to-noise ratio. Finally, we implement the optics and electronics responsible for the heterodyne measurement of the electric field. As a central objective of this project, measurements of coherent light transmission will be carried out through the sample of cold atoms, so that changes in the Beer-Lambert Law resulting from collective interactions resulting from the dense regime can be studied.

    • Pietro, Lucas Balan (IFSC-USP, Brazil): Dynamics of the evaporative cooling mechanism in a crossed optical dipole trap with tunable interactions

In this scientific initiation project, we propose to study the dynamics of the evaporative cooling process towards Bose-Einstein condensation in a potassium-39 atomic cloud trapped in a crossed optical trap. Using the Feshbach resonance technique capable of changing the atomic interaction of potassium-39 atoms, it will be possible to explore the competition between the increase in two-body collision rates, responsible for the thermalization of the atomic cloud, and the three-body losses in order to find the best experimental route for our experiment. In addition to the experimental work, the student will seek to develop models that simulate the dynamics of cooling and losses for our case. It is worth mentioning that this scholarship is a continuation of a project already carried out by the student during the year 2024 (Process: 2024/04325-6 – budget item of the PI project Process: 2022/02709-6), in which he developed the crossed optical trap in question and participated in the optimization of atomic trapping.

    • Pieve, Vinicius Tinano Pieve (UFSCAR, Brazil): Coherent Control of Collective Motion and Rydberg-dependent Gates

We will investigate how to ally the fast dynamics of internal Rydberg levels of ions with collective motional degrees of freedom. The effects of the huge Rydberg-ion polarizabilities on the collective motion will be harnessed to allow for a coherent control of the system and implement multi-ion entangling operations. The influence of Rydberg excitations will also be investigated in the limit over which motional excitations can be treated locally, opening the possibilities for the observation of quantum manybody phenomena.

    • Quinteros Moro, Felipe (Universidad de Concepción, Chile): Exact solution for deterministic delay-induced entanglement enhancement.

We investigate the non-Markovian dynamics of two fully excited two-level atoms coupled to a one-dimensional waveguide with time delays. Our study reveals how delayed photon exchange can synchronize atomic states, leading to the formation of an entangled dark state and a two-photon bound state in the continuum. This behavior includes the subfluorescence phenomenon, a counterpart to superfluorescence, where emission is suppressed rather than enhanced. These delay-induced effects highlight a spontaneous mechanism for generating and stabilizing entanglement between distant quantum emitters, offering promising applications for quantum networks and long-distance quantum communication system

    • Ramírez, Fabián Ignacio (Universidad de Chile, Chile): Spatial Correlation of Gaussian Beams in the FWM process

The generation and manipulation of correlated light is a key research focus due to its fundamental relevance in quantum optics and practical applications in emerging technologies. Entangled beams can be generated via the four-wave mixing (FWM) process, where two photons from a strong pump beam are converted into twin photons, forming probe and conjugate beams. Previous studies have demonstrated that the spatial structure of the entangled beams is governed by the pump’s angular spectrum and the phase-matching condition. In this work, we present a theoretical framework to describe the spatial correlations of the twin beams generated in FWM. We then analyze these correlations for both single and double Gaussian distributions of the pump and input probe beams.

    • Reis, Eduardo (Universidade Federal de São Carlos, Brazil): Collective Effects in the Light Emitted by Trapped Rydberg Ions

The main question behind this project is to understand how collective emission of light from trapped Rydberg ions, particularly superradiance, is affected, and potentially suppressed, by the presence of other atoms. For common geometries in a Paul trap (linear and zig-zag chains), we will thus investigate the role of interaction of an ensemble of Rydberg ions with other regular ions and also neutral atoms in Rydberg states on the collective scattering of light.

    • Révora, Corina (Instituto de Física de Buenos Aires (IFIBA-CONICET-UBA), Argentina): Superposition of n squeezed states for quantum metrology and for encoding quantum information

We present a method to systematically characterize highly non-classical states obtained by superposing n states that are squeezed along different directions. These states can be useful both for metrology, as they are highly sensitive to perturbations, and for encoding quantum information in a continuous variable system. We compare the results obtained for n=3 and n=4 with those arising from recent experiments performed with cold trapped ions, where so-called trisqueezed and quadsqueezed states have been prepared.

    • Rodrigues Da Paz, Rafael Aparecido (Instituto de Física de São Carlos, Brazil): Effects of quantum fluctuations in a bubble-shaped dipolar Bose-Einstein condensates

The possibility of experimental realization in microgravity on board the International Space Station has awakened great interest in spherical shell-shaped ultracold gases. Such geometry, associated with the anisotropic and long-range dipole-dipole interaction, gives rise to a system with unique characteristics. The addition of quantum fluctuations to energy balance has allowed the prediction of supersolid phase in this geometry. However, it is possible to better explore the scenarios of appearance of this new state. In this project, mainly through analytical methods, it is investigated the effects of the quantum fluctuations energy in the fundamental state of a bubble shaped dipolar Bose-Einstein condensate. It aims to deepen the knowledge about the characteristics and conditions of emergence of supersolids. For this purpose, it is expected to generate a phase diagram for this system that is as similar as possible to that obtained by numerical methods.

    • Sales, João Victor Macêdo (Universidade Federal do ABC, Brazil): Characterizing quantum correlations through multipartite steering of a four-wave mixing process in hot atomic vapors

Four-wave mixing (4WM) is an optical nonlinear process occurring in media with non-vanishing third-order susceptibility χ³, such as atomic vapors. In its stimulated version, it involves a pump beam and a seed beam injected into the medium, resulting in two amplified, entangled beams – the so-called probe and conjugate. This amplification, however, is inhomogeneous across the sideband spectrum, which indicates that the sideband modes present asymmetric entanglement properties. In order to better understand how these correlations are distributed, we study the multipartite quantum steering among four sideband frequency modes of a 4WM process in hot rubidium vapor cells. Instead of the usual phenomenological approach to 4WM, we employ a microscopic model based on the work of (Glorieux et. al, 2010), where the injected coherent fields interact with a four-level atom in a double-Λ configuration, resulting in squeezed, quantized modes of light. Using this microscopic description, we can capture the proper behavior of the quantum correlations that can be observed in the experiment, which the phenomenological model cannot fully describe. We compute the covariance matrix of the four sideband mode system and evaluate the multipartite steering and the monogamy relations among all the sideband modes. Our results reveal an asymmetric distribution and situations of non-monogamy relations of the quantum correlations among the sidebands modes distribution. This work provides a theoretical framework for understanding nonclassical correlations in 4WM-based quantum technologies.

    • Sallatti, Raphael Wictky (IFUSP, Brazil): Stability of dark solitons a bubble Bose-Einstein condensate

Dynamic stability of dark solitons produced in a Bose-Einstein condensate trapped on the surface of an ideal two-dimensional spherical bubble is investigated. In this spherical geometry, discrete unstable angular modes drive snake instabilities, with generation of vortex dipoles. A Bogoliubov- de Gennes analysis shows that most unstable mode determine the number of vortex dipoles. Time dependent simulations confirm the results.

    • Seguigne, Paul (Sorbonne Université, France): Perfect Optical Vortex Beams for photon entanglement

The Orbital Angular Momentum of light (OAM), carried by an optical vortex [1], has opened various applications, also in quantum optics because the possibility to create photonic OAM-pairs [2]. Its quantum nature and its large number of possible values make it relevant for high-dimensional entanglement. With Spontaneous Four Wave Mixing (SFWM), experienced in a rubidium vapor with Laguerre-Gaussian (LG) beams (the common class of vortex), it has been shown that the output indeed contains vortex pairs, even with large OAM [3][4]. However, because the pair generation relies on the overlap of all the involved vortices, and because the LG ring radius increases a lot with the OAM, the number of OAM-pairs is limited to some units. Our project investigates a new class of vortex beams, namely Perfect Vortex (PV) beams [5], to be applied to SFWM. We generate PV using an helical-conical phase realized by a phase-only SLM and show that their ring radius and thickness are OAM-independent over a wide OAM range. As consequence, we predict a strong increase in the number of OAM-pairs at the SFWM output compared to the LG case. This will open new features for OAM in quantum physics and quantum computing. Other applications of PV beams will be presented, as use for atom trapping. [1] L. Allen et al. Phys. Rev. A 12, 8185 (1992) [2] A. Mair et al. Nature 12, 313 (2001). [3] G. Walker, A. S. Arnold, S. Franke-Arnold, Trans-spectral orbital angular momentum transfer via four-wave mixing in Rb vapor, Phys. Rev. Lett. 12, 243601 (2012) [4] A. Chopinaud, M. Jacquey, B. Viaris de Lesegno, L. Pruvost, High helicity vortex conversion in a rubidium vapor, Phys. Rev. A.12, 063806 (2018) [5] P. Vaity, L. Rusch, Perfect Vortex Beam : Fourier transformation of Bessel Beam,Opt. Lett. 12, 000597 (2015)

    • Silva, Gregorio (Northwestern University, Brazil): Towards A CPT Atomic Clock Beyond The Standard Quantum Limit

Coherent population trapping (CPT) underpins compact atomic clocks technologies, and while spin squeezing techniques—such as one-axis twisting (OATS)—are established for enhancing sensitivity in Ramsey microwave clocks, their application to CPT clocks is nontrivial due to fundamental differences in the clock dynamics. I will present explicit adaptations of two OATS-based protocols—the Schrödinger cat state protocol (SCSP) and the echo squeezing protocol (ESP)—to Raman-Ramsey CPT clocks. The ESP enhances phase sensitivity by √(N/e), whereas the SCSP achieves an amplification factor of N/2, making the Heisenberg scaling sensitivity even in noisy environments increasingly within our experimental reach. The results demonstrate viable routes for quantum-enhanced precision in CPT-based timekeeping. [DOI: 10.1103/PhysRevA.106.01311]

    • Silva, Thiago Teixeira Xavier Da (Ufscar-SP, Brazil): Simulation of a Quantum Trampoline for cold atoms

This work investigates, through theoretical–numerical modeling, the “quantum tram- poline” applied to ultracold 88Sr atoms at the StrontiumLab2. Starting from the time- dependent Schrödinger equation, we simulate sequences of rectangular Bragg pulses and compute the suspended fraction as a function of pulse period, initial cloud temperature, and number of interactions. We show that, at typical temperatures of ∼1 μK, the visibility of the resonances around the classical-trampoline period Tc ≃1.34 ms decreases rapidly with increasing number of pulses, yet still reaches measurable values (≳ 14%) for sequences of 6–10 pulses with τ = 35 μs . We identify Doppler broadening as the main coherence- limiting factor. The results provide clear operational parameters for future high-precision gravimetry trials and establish the “quantum trampoline” as a promising platform for quantum sensing.

    • Silva, Washington Pantoja (Universidade Federal de São Carlos -UFSCAR, Brazil): Tuning photon-photon correlations with state preparation and spatial configuration

Understanding and controlling the statistical properties of light emitted by atomic ensembles is a central goal in quantum optics. We present a theoretical study of the second-order correlation function $g^{(2)}(0)$ in externally driven two-level atomic ensembles, based on a density matrix approach with collective dipole operators. Extending previous results, we compare the two-photon correlations of the light radiated by three types of atomic-state preparations: mixed states, coherent states, and number states, all with equal excited-state populations. We show that the photon statistics are highly sensitive to the atomic state. Indeed, coherent states enhance both superbunching and antibunching, while number states can suppress or sharpen spatial fluctuations of the photon-photon correlations depending on the emission direction. We also explore the impact of spatial order and disorder, finding that nonclassical correlations persist even in randomly distributed atomic ensembles. These findings demonstrate that quantum state preparation and spatial configuration are two powerful tools in shaping the statistical properties of scattered light.

    • Sousa, Aryadine (Universidade Federal do ABC, Brazil): Quantum Information and Thermodynamics of optically pumped magnetometers based on Spin-Exchange collisions of hybrid species

Optically pump magnetometers based on hybrid vapor cells provide a robust platform to study quantum interactions mediated by spin-exchange collisions. We theoretically investigate how the optical pumping affects the spin state preparation of both species. By modeling the spin-exchange dynamics for dense media, we analyze the evolution of both atomic spin states and thermodynamic properties of the system. We also investigate the quantum information properties of such kind of dynamics, in which we study the mutual information to quantify the information shared between the species, and the entanglement produce by the collisions. We also study how this quantum properties determine the sensitivity of this kind of magnetometers. This kind of approach can be apply to the interaction of alkali atoms with noble-gases which can be further used as an interface for hour-long quantum memories and entanglement source at room-temperature.

    • Tacca, Letícia Lira (Universidad de Concepción, Chile): HONG-OU-MANDEL INTERFERENCE WITH MULTIPORT PHOTONIC DEVICES

The Hong-Ou-Mandel (HOM) effect, a hallmark of quantum interference, has been extensively studied in two-port systems but remains less explored in multiport photonic devices. In this work, we experimentally characterize HOM interference in multiport photonic circuits, demonstrating its potential for high-precision measurements and quantum information processing. Using integrated photonic platforms, we observe non-classical photon bunching and anti-bunching effects across multiple output ports, revealing new interference regimes beyond traditional two-photon physics. As an example of a key application of our research, we measure intercore differential delay in multicore fibers, where multiport HOM interference provides a quantum-enhanced method for characterizing propagation delays with sub-picosecond resolution. This technique could significantly improve performance in quantum communications, distributed sensing, and photonic network synchronization. Additionally, our results suggest new avenues for implementing multi-channel quantum gates and high-dimensional entanglement generation in integrated photonic systems. The experimental setup combines superconducting single-photon detectors with tunable delay lines to map the multiport interference landscape. Theoretical simulations closely match our observations, validating the model for future device optimization. These findings advance fundamental understanding of quantum interference in complex photonic systems while offering practical tools for quantum metrology and communication technologies.

    • Terán Cisneros, César Enrique (Instituto de Física, Universidad Nacional Autónoma de México, Mexico): Formation and dynamics of band gap solitons in high-reflectance optical cavities

We investigate the theoretical and experimental feasibility of forming band gap solitons in a quasi-one-dimensional Bose-Einstein condensate confined by an optical potential generated within a high-reflectance cavity. The cavity mode is driven by a quasi-resonant longitudinal pump beam. Given the coupled dynamics of light and matter, we analyze the existence and dynamical stability of these solitons, comparing scenarios with and without the cavity.

    • Torrico Chávez, César Abraham (PPGCIMAT-Universidade Federal do Rio Grande do Sul, Brazil): Ubiquity of tricorn-like structures in the parameter plane of non-linear dynamical systems

In this work we give numerical evidence of the existence of tricorn-like structures of stable periodic orbits (SPOs) in the parameter plane of: a complex cubic map, the Lorenz-84 climate model, an optically injected semiconductor laser and a quantum dot semiconductor laser with optical injection, which leads us to conjecture the ubiquity of this type of structures in the parameter space of different discrete and continuous-time dynamical systems.

    • Uhthoff-Rodríguez, Leonardo (Institute of Physics, National Autonomous University of Mexico., Mexico): Fast Magnetic Coil Controller for Cold Atom Experiments

Cold atoms experiments employ magnetic fields, commonly generated by coils, as an essential tool to control and manipulate atomic samples. In these experiments, it is often necessary to rapidly switch the magnetic field between two values. However, typical power supplies have a limited switching time for the current flowing through the coil that is inversely proportional to the maximum voltage they can supply and directly proportional to the inductance of the coil. We present a control scheme implemented as an electronic circuit that overcomes this limitation, a faster control is achieved by momentarily applying an on-demand high voltage when the control signal variation surpasses the limits that the conventional power supply can follow, allowing a faster current flow into the magnetic coil. In our specific application, we show that with this control the coil current can follow control signals continuously from negative to positive and vice versa with a ~5 kHz bandwidth and a maximum switching speed of ~40 μs between -1A and 1 A even though the time constant of the coil is of ~2 ms. Improving by more than a factor of ten the bandwidth and making the switching speed 20 times faster than that of a typical power supply. By appropriately selecting the components of the circuit, the switching time and the bandwidth can be finely tuned to any desired value. Moreover, our scheme can be easily adapted to different applications within a wide range of inductive and power requirements.

    • Vivi, Giovanni (UFSCar, Brazil): Propagação de Ondas Mecânicas em Cadeias de Íons com Excitações de Rydberg

investigar o efeito das excitações de Rydberg na dinâmica clássica de ondas mecânicas propagando em diferentes arranjos de cristais de íons aprisionados. O problema dos íons aprisionados, interagindo via forças de Coulomb, pode ser mapeado em um sistema de massas e molas acopladas, com seu movimento coletivo decomposto em um conjunto de modos normais.

    • Vlatko, Carolina (Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires / CONICET – Instituto de Física de Buenos Aires, Argentina): Vibrational dynamics in ultracold ion systems

Our research proposal focuses on the vibrational dynamics of small trapped ion crystals, combining theoretical modeling and experimental implementation at the Cold Ions and Atoms Laboratory (LIAF). Initial efforts target the characterization of vibrational states in individual ions under the Gaussian approximation, including coherent and squeezed states. These techniques will be extended to small ion chains to study entanglement dynamics in systems coupled to engineered baths via laser beams. References [1] Cecilia Cormick and Juan Pablo Paz. Observing different phases for the dynamics of entanglement in an ion trap. Phys. Rev. A, 81:022306, Feb 2010.

    • Zapana Choquehuanca, John Milton (Universidade Federal Fluminense, Brazil): Ergotropy-Based Quantum Thermodynamics

We introduce an ergotropy-based formulation of quantum thermodynamics, which provides a strong connection between average heat and von Neumann entropy. By adopting this formulation, we can reinterpret the infinitesimal average heat in terms of the infinitesimal change of the passive state associated with the density operator behind the quantum dynamics. Such as entropy, this leads to a heat concept that is invariant under passive state transformations. As an application, the average heat can be used as a general non-Markovinity measure for unital maps. Moreover, a positive-semidefinite temperature naturally emerges in an out-of-equilibrium ergotropy-based scenario. Concerning the infinitesimal average work, it arises as the infinitesimal variation of ergotropy, as well as an extra passive work contribution in the case of a time-dependent Hamiltonian. As illustrations, we consider the thermodynamics of a single-qubit open system in the cases of generalized amplitude-damping and phase-damping channels.

  • Arpan Chatterjee (arpanchatterjee1995@gmail.com, Brazil): Nonlinearity and temperature dependence of drive-induced shifts in a thermal environment

Drive-induced shifts, such as ac Stark shift and Bloch-Siegert shift, are routinely used in various spectroscopies. These shifts are experimentally known to show dispersive Lorentzian behavior as a function of its characteristic frequencies in optical pumping experiments. However, the drive-induced Stark shifts, as calculated using Floquet or dressed atom approaches, do not show the above nonlinear behavior. To address this, we theoretically investigated the drive-induced shifts using a previously reported fluctuation-regulated quantum master equation [A. Chakrabarti and R. Bhattacharyya, Phys. Rev. A 97, 063837 (2018)]. The shifts are obtained as closed-form expressions over the entire detuning range of the drive. The predicted shifts match satisfactorily with the known experimental data of the light shifts. We show that the calculated shifts are a Kramers-Kronig pair of the drive-induced dissipation in conformity with experimental findings. Moreover, we show that at low temperatures, i.e., for less thermal fluctuations, our results asymptotically match with the known theoretical form of the shifts. In the high-temperature regime, we predict that the shifts decrease in magnitude and are inversely proportional to the square of the temperature.

 

Registration

Announcement:

Application deadline: July 23, 2025 (closed)

Program

 The schedule might be changed.

Videos and Files


2025-10-20 2025-10-21 2025-10-22 2025-10-23 2025-10-24 2025-10-27 2025-10-28 2025-10-29 2025-10-30
  • 09:00 - Thereza Paiva (UFRJ, Brazil): Optical lattices - Class 2
  • 11:00 - Carla Hermann-Avigliano (University of Chile, Chile): Hands-on Scientific Communication: From Writing to Presenting Your Research - Class 3
  • 15:00 - Michel Brune (ENS + Collège de France, France): From cavity QED to quantum simulations with circular Rydberg atoms - Class 4
2025-10-31
  • 09:00 - Michel Brune (ENS + Collège de France, France): From cavity QED to quantum simulations with circular Rydberg atoms - Class 5
  • 11:00 - Thereza Paiva (UFRJ, Brazil): Optical lattices - Class 3
  • 14:00 - Stephen Walborn (Universidad de Concepción, Chile): Quantum information processing with photons - Class 3
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Venue

Venue: The event will be held at IFT-UNESP, located at R. Jornalista Aloysio Biondi, 120 – Barra Funda, São Paulo. The easiest way to reach us is by subway or bus, See arrival instructions here.

Accommodation: Participants whose accommodation will be provided by the institute will stay at Hotel Intercity the Universe Paulista. Hotel recommendations are available here.

Attention! Some participants in ICTP-SAIFR activities have received email from fake travel agencies asking for credit card information. All communication with participants will be made by ICTP-SAIFR staff using an e-mail “@ictp-saifr.org”. We will not send any mailings about accommodation that require a credit card number or any sort of deposit. Also, if you are staying at Hotel Intercity the Universe Paulista, please confirm with the Uber/Taxi driver that the hotel is located at Rua Pamplona 83 in Bela Vista (and not in Jardim Etelvina).

Additional Information

BOARDING PASS: All participants, whose travel has been provided or will be reimbursed by ICTP-SAIFR, should bring the boarding pass  upon registration. The return boarding pass (PDF, if online check-in, scan or picture, if physical) should be sent to secretary@ictp-saifr.org by e-mail.

Visa information: Nationals from several countries in Latin America and Europe are exempt from tourist visa. Nationals from Australia, Canada and USA are required to apply for a tourist visa.

Poster presentation: Participants who are presenting a poster MUST BRING A PRINTED BANNER . The banner size should be at most 1 m (width) x 1,5 m (length). We do not accept A4 or A3 paper.

Power outlets: The standard power outlet in Brazil is type N (two round pins + grounding pin). Some European devices are compatible with the Brazilian power outlets. US devices will require an adapter.