Sergio Ricardo Muniz

University of São Paulo | USP · Institute of Physics São Carlos (IFSC)

Josephson junctions are essential ingredients in the superconducting circuits used in many existing quantum technologies. Additionally, ultracold atomic quantum gases have also become essential platforms to study superfluidity. Here, we explore the analogy between superconductivity and superfluidity to present an intriguing effect caused by a thin...

Considering the paradigmatic driven Brownian motion, we perform extensive numerical analysis on the performance of optimal linear-response processes far from equilibrium. We focus on the overdamped regime where exact optimal processes are known analytically and most experiments operate. This allows us to compare the optimal processes obtained in li...

Nitrogen-vacancy (NV) and other color centers in diamond have attracted much attention as non-photobleaching quantum emitters and quantum sensors. Since microfabrication in bulk diamonds is technically difficult, embedding nanodiamonds with color centers into designed structures is a way to integrate these quantum emitters into photonic devices. In...

Given the remarkable developments in synthetic control over chemical and physical properties of colloidal particles, it is interesting to see how stochastic thermodynamics studies may be performed with new, surrogate, or hybrid model systems. In the present work, we apply stochastic dynamics and nonlinear optical light-matter interaction simulation...

Among hundreds of impurities and defects in diamond, the nitrogen-vacancy (NV) center is one of the most interesting to be used as a platform for quantum technologies and nanosensing. Traditionally, synthetic diamond is irradiated with high-energy electrons or nitrogen ions to generate these color-centers. For precise positioning of the NV centers,...

Polymeric microresonators embedded with nanodiamonds containing NV ⁻ color-centers were fabricated via two-photon polymerization technique, presenting Q factors in the order of 10 ⁴ , and one to three fluorescent nanodiamonds per structure.

Among hundreds of impurities and defects in diamond, the nitrogen-vacancy (NV) center is one of the most interesting to be used as a platform for quantum technologies and nanosensing. Traditionally, synthetic diamond is irradiated with high-energy electrons or nitrogen ions to generate these color-centers. For precise positioning of the NV centers,...

Among hundreds of impurities and defects in diamond, the nitrogen-vacancy (NV) center is one of the most interesting to be used as a platform for quantum technologies and nanosensing. Traditionally, synthetic diamond is irradiated with high-energy electrons or nitrogen ions to generate these color-centers. For precise positioning of the NV centers,...

In recent years, nitrogen-vacancy (NV) color centers in diamond have become excellent solid-state quantum sensors due to their electronic spin properties. Especially for their easy optical initialization and detection, together with their very large spin coherence at room temperature. Many studies have reported their use for sensing temperature, st...

Due to their versatility in investigating phenomena in microscopic scales, optical tweezers have been an excellent platform for studying stochastic thermodynamics. In this context, this work presents experimental measurements of the energetic cost of driven finite-time protocols using colloidal Brownian particles in harmonic potentials. For this si...

We describe here* the construction and characterization of a high-resolution optical magnetometer to measure the full vector magnetic field on an ultrathin layer near the surface of the device. This solid-state device is based on quantum sensors created by a layer of nitrogen-vacancy (NV) centers less than 20 nm below the surface of an ultrapure di...

One of the biggest challenges to implement quantum protocols and quantum information processing (QIP) is achieving long coherence times, usually requiring systems at ultra-low temperatures. The nitrogen-vacancy (NV) center in diamond is a promising alternative to this problem. Due to its spin properties, easy manipulation, and the possibility of do...

We describe here a method to generate high-definition arbitrary laser beam shapes and profiles useful to many applications, ranging from optical patterning and lithography to optical trapping of microscopic particles and ultracold atoms. The phase contrast between a binary grating and a targeted intensity distribution is encoded on a spatial light...

This preliminary* study presents a simple modulation scheme to dynamically create time-averaged optical potentials to trap colloidal particles using acousto-optical modulation. The method provides access to control experimentally relevant parameters of a tunable double-well potential. We show experimental data successfully adjusting the trapping di...

Josephson junctions are essential ingredients in the superconducting circuits used in many existing quantum technologies. Additionally, ultracold atomic quantum gases have also become essential platforms to study superfluidity. Here, we explore the analogy between superconductivity and superfluidity to present an intriguing effect caused by a thin...

Considering the paradigmatic driven Brownian motion, we perform extensive numerical analysis on the performance of optimal linear-response processes far from equilibrium. We focus on the overdamped regime where exact optimal processes are known analytically, and most experiments operate. This allows us to compare the optimal processes obtained in l...

Given the remarkable developments in synthetic control over colloidal particle chemical and physical properties, it is interesting to see how stochastic thermodynamics studies may be performed with new, surrogate, or hybrid model systems. In the present work, we apply stochastic dynamics and nonlinear optical light-matter interaction simulations to...

Complex chiral particles Synthetic colloids are usually smooth, but nature can produce micrometer-scale particles with intricate structure and shape, such as the coccoliths produced by algae. Jiang et al. controlled the self-assembly of gold–cysteine nanoplatelets into a variety of chiral, hierarchically organized colloidal particles by changing th...

Teaching and learning strategies that use innovating technologies, such as the development of software or an understanding of the theoretical concepts of analytical equipment, can be essential tools for the construction of knowledge. In this way, this work describes the construction of an innovative and low-cost colorimeter using a RGB LED and a mi...

We report a proof-of-concept micro-spectroscopy, stochastic dynamics, and optical trapping study of a well-known reaction for methylene blue photodegradation catalyzed by titanium dioxide aggregates and nanotubes. Photocatalysis is performed under a high concentration of reactants and catalyst loading to characterize the fundamental chemical kineti...

Resumo O ganho de aprendizado conceitual em disciplinas introdutórias de Física para alunos ingressantes na universidade, submetidos a diferentes abordagens metodológicas, foi medido com um instrumento padronizado internacionalmente reconhecido. O estudo envolveu 599 estudantes de engenharia, física e matemática do campus da USP de São Carlos, no p...

Resumo O presente estudo investigou as orientações motivacionais de estudantes do Ensino Médio em relação à disciplina de Física e buscou contribuir com o aprofundamento da discussão acerca da proposição e validação de instrumentos de medidas de variáveis psicológicas. Foi utilizada a Escala de Motivação: Atividades Didáticas de Física (EMADF) para...

Although diamond photonics has driven considerable interest and useful applications, as shown in frequency generation devices and single photon emitters, fundamental studies on the third-order optical nonlinearities of diamond are still scarce, stalling the development of an integrated platform for nonlinear and quantum optics. The purpose of this...

Although diamond photonics has driven considerable interest and useful applications, as shown in frequency generation devices and single photon emitters, fundamental studies on the third-order optical nonlinearities of diamond are still scarce, stalling the development of an integrated platform for nonlinear and quantum optics. The purpose of this...

We apply the global thermodynamic variables approach to experimentally determine the isother-mal compressibility parameter κT of a trapped Bose gas across the phase transition. We demonstrate the behavior of κT around the critical pressure, revealing the second order nature of the phase transition. Compressibility is the most important susceptibili...

The study of the thermodynamic properties of trapped gases has attracted great attention during the last few years and can be used as a tool to characterize such clouds in the presence of other phenomena. Here, we obtain an equation of state for a harmonically trapped Bose–Einstein condensate taking the limit of by means of global themodynamic vari...

We apply the global thermodynamic variables approach to experimentally determine the isothermal compressibility parameter κT of a trapped Bose gas across the phase transition. We demonstrate the behavior of κT around the critical pressure, revealing the second-order nature of the phase transition. Compressibility is the most important susceptibilit...

In a region free of currents, magnetostatics can be described by the Laplace equation of a scalar magnetic potential, and one can apply the same methods commonly used in electrostatics. Here, we show how to calculate the general vector field inside a real (finite) solenoid, using only the magnitude of the field along the symmetry axis. Our method d...

Phase transitions are well understood and generally followed by the behavior of the associated thermodynamic quantities, such as in the case of the $\lambda$ point superfluid transition of liquid helium, which is observed in its heat capacity. In the case of a trapped Bose-Einstein condensate (BEC), the heat capacity cannot be directly measured. In...

Phase transitions are well understood and generally followed by the behavior of the associated thermodynamic quantities, such as in the case of the λ point superfluid transition of liquid helium, which is observed in its heat capacity. In the case of a trapped Bose-Einstein condensate (BEC), the heat capacity cannot be directly measured. In this wo...

We generalize the superfluid hydrodynamic equations to describe the expansion of a turbulent condensate cloud. Our Lagrangian formalism includes the kinetic energy associated with an entangled vortex configuration. The expressions developed here clarify the physics behind the self-similar free expansion as seen in experiments. This feature is a cru...

We generalize the superfluid hydrodynamic equations to describe the expansion of a turbulent condensate cloud. Our Lagrangian formalism includes the kinetic energy associated with an entangled vortex configuration. The expressions developed here clarify the physics behind the self-similar free expansion as seen in experiments. This feature is a cru...

In spite of being a phenomenon studied over centuries, turbulence remains an intriguing phenomenon of nature. In the low temperature regime, turbulence has been investigated in superfluid helium during the last decades. Due to the quantum nature of superfluids, this phenomenon is named Quantum Turbulence and it is characterized by a particular conf...

Quantum gases became an important cross-disciplinary tool in contemporary physics. Here we present the development of new methods to produce and control engineered arbitrary optical potentials to create dynamical quantum simulators of condensed matter systems.

Using the concept of global variables to describe the thermodynamics properties of a trapped Bose-Einstein Condensate we have performed an experiment with a BEC of 87Rb trapped in a hybrid trap. Then, it is possible to extend our study to different geometries of the system, going from an almost spherical BEC to a very elongated axial symmetric trap...

In a region free of currents, magnetostatics can be described by the Laplace equation of a scalar magnetic potential, and one can apply the same methods commonly used in electrostatics. Here we show how to calculate the general vector field inside a real (finite) solenoid, using only the magnitude of the field along the symmetry axis. Our method do...

Partial-transfer absorption imaging is a tool that enables optimal imaging of atomic clouds for a wide range of optical depths. In contrast to standard absorption imaging, the technique can be minimally destructive and can be used to obtain multiple successive images of the same sample. The technique involves transferring a small fraction of the sa...

In a recent study we demonstrated the emergence of turbulence in a trapped Bose-Einstein conden-sate of 87 Rb atoms. An intriguing observation in such a system is the behavior of the turbulent cloud during free expansion.The aspect ratio of the cloud size does not change in the way one would expect for an ordinary non-rotating (vortex-free) condens...

We have created a long-lived (≈40 s) persistent current in a toroidal Bose-Einstein condensate held in an all-optical trap. A repulsive optical barrier across one side of the torus creates a tunable weak link in the condensate circuit, which can affect the current around the loop. Superflow stops abruptly at a barrier strength such that the local f...

In a recent study we demonstrated the emergence of turbulence in a trapped Bose-Einstein condensate of Rb-87 atoms. An intriguing observation in such a system is the behavior of the turbulent cloud during free expansion.The aspect ratio of the cloud size does not change in the way one would expect for an ordinary non-rotating (vortex-free) condensa...

We have created a long-lived (≈ 40 s) persistent current in a toroidal Bose-Einstein condensate held in an all-optical trap. A repulsive optical barrier across one side of the torus creates a tunable weak link in the condensate circuit, which can affect the current around the loop. Superflow stops abruptly at a barrier strength such that the local...

We study the phase-fluctuating condensate regime of ultra-cold atoms trapped in a ring-shaped trap geometry, which has been realized in recent experiments. We first consider a simplified box geometry, in which we identify the conditions to create a state that is dominated by thermal phase-fluctuations, and then explore the experimental ring geometr...

We study the phase-fluctuating condensate regime of ultra-cold atoms trapped in a ring-shaped trap geometry, which has been realized in recent experiments. We first consider a simplified box geometry, in which we identify the conditions to create a state that is dominated by thermal phase-fluctuations, and then explore the experimental ring geometr...

In a region free of currents, magnetostatics can be described by the Laplace equation of a scalar magnetic potential, and one can apply the same methods commonly used in electrostatics. Here we show how to calculate the general vector field inside a real (finite) solenoid, using only the magnitude of the field along the symmetry axis. Our method do...

We are investigating the stability of persistent flow in a toroidal BEC. The BEC is held in a red-detuned optical trap formed by two beams: a tightly focused ``sheet'' of light providing tight vertical confinement, and a Laguerre-Gaussian beam confining the BEC to a ring in the radial direction. To this trap we have added a blue-detuned light sheet...

We demonstrate Bose-Einstein condensation of atoms in an all-optical ring geometry, created by the intersection of a horizontal sheet-like trapping beam and a vertical ring-shaped trapping beam. The BEC is continuous azimuthally around the ring. By tuning the relative intensities of the trapping beams, we can make a continuous transition from an el...

In most cold atom experiments obtaining an image of the atomic cloud involves destroying the sample. Phase-contrast imaging can be used to get spatial density information with minimal perturbation of the sample, however, poor detection efficiency can greatly reduce the signal to noise ratio (S/N) obtained. We present a method which uses the ground...

An interacting Bose-Einstein Condensate (BEC) is expected to exhibit superfluidity, and persistent currents in a magnetically trapped, toroidal shaped BEC have been seen lasting up to 10 seconds [1]. We have recently performed experiments in a ring-shaped optical dipole trap, formed by the combination of a Laguerre-Gaussian beam intersecting a ligh...

There is a lot of interest in studying degenerate quantum gases in various types of confining potentials, to explore effects ranging from quantum transport to quantum information. More recently, spatial light modulators have been proposed to produce generalized optical potentials. Here we present a particular kind of spatial-light modulation techni...

We have realized a conical matter wave lens. The repulsive potential of a focused laser beam was used to launch a Bose-Einstein condensate into a radially expanding wavepacket whose perfect ring shape was ensured by energy conservation. In spite of significant interactions between atoms, the spatial and velocity widths of the ring along its radial...

We have realized a conical matter wave lens. The repulsive potential of a focused laser beam was used to launch a Bose-Einstein condensate into a radially expanding wavepacket whose perfect ring shape was ensured by energy conservation. In spite of significant interactions between atoms, the spatial and velocity widths of the ring along its radial...

Gaseous Bose-Einstein condensates (BECs) have become an important test bed for studying the dynamics of quantized vortices. In this work we use two-photon Doppler sensitive Bragg scattering to study the rotation of sodium BECs. We analyze the microscopic flow field and present laboratory measurements of the coarse-grained velocity profile. Unlike t...

Gaseous Bose-Einstein condensates (BECs) have become an important test bed for studying the dynamics of quantized vortices. In this work we use two-photon Doppler sensitive Bragg scattering to study the rotation of sodium BECs. We analyze the microscopic flow field and present laboratory measurements of the coarse-grained velocity profile. Unlike t...

Multi-species mixtures of ultracold atoms are currently being studied intensively. The areas of focus include, but are not limited to condensed matter and quantum statistical effects, interaction-tuning by photo- and magneto-association, production of (degenerate) ultracold molecules, and so on. In the specific case of NaRb, predictions exist regar...

We have created a trapped BEC whose spin orientation is metastable in an external, inhomogeneous magnetic field. This trapping field can in principle be used to coherently control the coupling between spin and spatial wavefunctions. Although subject to Majorana losses, we've noticed lifetimes of a few hundred milliseconds. Atoms held in the trap fo...

We have measured the velocity field of a vortex lattice within a sodium Bose-Einstein condensate using Bragg scattering. The phase gradient of the macroscopic wave function was mapped into the spatial structure of the diffracted atom cloud, allowing for the single shot measurement of the rotation parameters. A combination of spectral and spatial in...

Gaseous Bose-Einstein condensates (BECs) have become an important test bed for studying the dynamics of quantized vortices. We used two-photon Doppler sensitive Bragg scattering to study the rotation of sodium BECs, particularly to measure the velocity field of a vortex lattice within the condensate. Unlike time-of-flight imaging, Bragg scattering...

We have measured the velocity field of a vortex lattice within a sodium Bose-Einstein condensate using Bragg scattering. The phase gradient of the macroscopic wavefunction was mapped into the spatial structure of the diffracted atom cloud, allowing for single shot measurement of the rotation parameters. A combination of spectral and spatial informa...

We have created a Bose-Einstein condensate whose spin orientation is metastable. Condensates were transferred into a quadrupole magnetic trap, where Majorana transitions limited the lifetime to a few hundred milliseconds, about 30 times the trapping period. Atoms held in the trap frequently displayed a ring-shaped time-of-flight distribution. We sp...

We have created a Bose-Einstein condensate whose spin orientation is metastable. Condensates were transferred into a quadrupole magnetic trap, where Majorana transitions limited the lifetime to a few hundred milliseconds, about 30 times the trapping period. Atoms held in the trap frequently displayed a ring-shaped time-of-flight distribution. We sp...

In this paper we extend previous hydrodynamic equations, governing the motion of Bose-Einstein-condensed fluids, to include temperature effects. This allows us to analyze some differences between a normal fluid and a Bose-Einstein-condensed one. We show that, in close analogy with superfluid He-4, a Bose-Einstein-condensed fluid exhibits the mechan...

Using a system composed of a Quadrupole and Ioffe Configuration (QUIC) trap loaded from a slowed atomic beam, we have performed experiments to observe the Bose-Einstein Condensation of Na atoms. In order to obtain the atomic distribution in the trap, we use an in situ out of resonance absorption image through a probe beam, to determine temperature...

Using a shaking field overlaped to the static field of a quadrupole trap we have performed experiments with cold Na atoms held in a magnetic trap. As a function of the shaking frequency the temperature of the atomic cloud is measured by timeof-flight. We observe results similar to Kumakura et al. [Phys. Rev. A 68, 021401(R)] and the variations of t...

This communication describes the observation of a new type of dark spontaneous-force optical trap (dark SPOT) obtained without the use of a mask blocking the central part of the repumper laser beam. We observe that loading a magneto-optical trap (MOT) from a continuous and intense flux of slowed atoms and by appropriately tuning the frequency of th...

This communication describes the observation of a new type of dark spontaneous-force optical trap (dark SPOT) obtained without the use of a mask blocking the central part of the repumper laser beam. We observe that loading a magneto-optical trap (MOT) from a continuous and intense flux of slowed atoms and by appropriately tuning the frequency of th...

Using the dark spot slowing technique we have measured the capture velocity of a sodium magneto-optical trap as a function of trap laser intensity. The comparison with calculations based on a simple model allows us to obtain the escape velocity. Using this intensity dependent escape velocity and the Gallagher-Pritchard model [Phys. Rev. Lett., 63,...

We use a dark-spot Zeeman-tuned slowing technique to measure the capture velocity in a sodium magneto-optical trap as a function of the trapping laser intensity. We expand on previous work by measuring the capture velocity over a broad range of light intensities. We observe that the capture velocity reaches a maximum value and then decreases with i...