arXiv subjects

Celso Jorge Villas-Boas

Publications and source records attributed to Celso Jorge Villas-Boas.

8 recordsLinked to original sources

arXiv2026

Efficiency-Resolved Recovery Dynamics of an Free-Running InGaAs/InP Single Photon Avalanche Detector Operated in Gated Mode

Detection efficiency in gated-mode single-photon avalanche detectors recovers gradually after each gate edge, limiting attainable count rates, yet quantitative recovery models exist only for free-running operation. We extract the gated recovery time constant of a free-running InGaAs/InP detector at 1550 nm by sweeping the gate frequency from 100 kHz to 1 MHz and globally fitting count rates across four dead times, requiring neither a pulsed laser nor a time-to-digital converter. The recovery time decreases linearly with detection efficiency, from 301 to 161 ns between 10 % and 25 %, at 9.3 ns per percentage point. We further resolve a periodic count-rate modulation consistent with bias-dependent capacitive gate feedthrough.

quant-ph↗

arXiv2025

Dark States of Light and the Hidden Energy in Thermal Radiation Detection

We develop a quantum-optical framework demonstrating that thermal radiation can confine a significant portion of its energy in dark collective modes -- highly entangled photon states that, despite their photonic nature, remain decoupled from matter through standard electromagnetic interactions. In a system comprising $M$ thermal field modes, we show that only a fraction $1/M$ of the total energy is accessible to matter, while the remaining $(M-1)/M$ is stored in dark states, rendering it undetectable by conventional electromagnetic means. We also demonstrate that intensity measurements, commonly used to estimate field energy, can be misleading due to collective effects that suppress or enhance light-matter coupling. To explore further this phenomenon, we analyze a cavity QED model enclosing a single dissipative atom and show that symmetry breaking in the atom-field interaction enables access to the hidden energy stored in dark modes. While inconclusive, these findings suggest that dark states of light may underlie certain unexplained energy phenomena, pointing to a possible microscopic mechanism based on the collective structure of thermal radiation.

quant-ph↗

arXiv2025

MixFunn: A Neural Network for Differential Equations with Improved Generalization and Interpretability

We introduce MixFunn, a novel neural network architecture designed to solve differential equations with enhanced precision, interpretability, and generalization capability. The architecture comprises two key components: the mixed-function neuron, which integrates multiple parameterized nonlinear functions to improve representational flexibility, and the second-order neuron, which combines a linear transformation of its inputs with a quadratic term to capture cross-combinations of input variables. These features significantly enhance the expressive power of the network, enabling it to achieve comparable or superior results with drastically fewer parameters and a reduction of up to four orders of magnitude compared to conventional approaches. We applied MixFunn in a physics-informed setting to solve differential equations in classical mechanics, quantum mechanics, and fluid dynamics, demonstrating its effectiveness in achieving higher accuracy and improved generalization to regions outside the training domain relative to standard machine learning models. Furthermore, the architecture facilitates the extraction of interpretable analytical expressions, offering valuable insights into the underlying solutions.

cs.LG↗

arXiv2023

Collateral coupling between superconducting resonators: Fast and high fidelity generation of qudit-qudit entanglement

Superconducting circuits are highly controllable platforms to manipulate quantum states, which make them particularly promising for quantum information processing. We here show how the existence of a distance-independent interaction between microwave resonators coupled capacitively through a qubit offers a new control parameter toward this goal. This interaction is able to induce an idling point between resonant resonators, and its state-dependent nature allows one to control the flow of information between the resonators. The advantage of this scheme over previous one is demonstrated through the generation of high-fidelity NOON states between the resonators, with a lower number of operations than previous schemes. Beyond superconducting circuits, our proposal could also apply to atomic lattices with clock transitions in optical cavities, for example.

quant-ph↗

arXiv2023

Single-shot measurements of phonon number states using the Autler-Townes effect

We present a single-shot method to measure motional states in the number basis. The technique can be applied to systems with at least three non-degenerate energy levels which can be coupled to a linear quantum harmonic oscillator, such as in trapped ion experiments. The method relies on probing an Autler-Townes splitting that arises when two levels are strongly coupled via a phonon-number changing transition. We demonstrate the method using a single trapped ion and show that it may be used in a non-demolition fashion to prepare phonon number states. We also show how the Autler-Townes splitting can be used to measure phonon number distributions.

quant-ph↗

arXiv2021

Continuous quantum light from a dark atom

Cycling processes are important in many areas of physics ranging from lasers to topological insulators, often offering surprising insights into dynamical and structural aspects of the respective system. Here we report on a quantum-nonlinear wave-mixing experiment where resonant lasers and an optical cavity define a closed cycle between several ground and excited states of a single atom. We show that, for strong atom-cavity coupling and steady-state driving, the entanglement between the atomic states and intracavity photon number suppresses the excited-state population via quantum interference, effectively reducing the cycle to the atomic ground states. The system dynamics then result from transitions within a harmonic ladder of entangled dark states, one for each cavity photon number, and a quantum Zeno blockade that generates antibunching in the photons emitted from the cavity. The reduced cycle suppresses unwanted optical pumping into atomic states outside the cycle, thereby enhancing the number of emitted photons.

quant-ph↗

arXiv2020

Photon-photon Correlations from a Pair of Strongly Coupled Two-Level Emitters

We investigate two-color photon correlations in the light emitted by strongly coupled two-level emitters. Spectral filtering allows us to manipulate the collected light statistics and we show that the resonances induced by dipole-dipole interactions give rise to specific correlations, where the time-symmetry of the correlations is broken. Based on the collective dressed states, our study encompasses both the case of real processes, where the photons are associated with specific resonances and classical correlations between each other, and virtual processes, where pairs of photons are emitted with non-classical correlations.

quant-ph↗

arXiv2019

Cooperative spontaneous emission via renormalization approach: Classical versus semi-classical effects

We address the many-atom emission of a dilute cloud of two-level atoms through a renormalized perturbation theory. An analytical solution for the truncated coupled-dipole equations is derived, which contains an effective spectrum associated to the initial conditions. Our solution is able to distinguish precisely classical from semi-classical predictions for large atomic ensembles. This manifests as a reduction of the cooperativity in the radiated power for higher atomic excitation, in disagreement with the fully classical prediction from linear optics. Moreover, the second-order cooperative emission appears accurate over several single atom lifetimes and for interacting regimes stronger than those permitted in conventional perturbation theory. We can compute the semiclassical dynamics of hundred thousand of interacting atoms with ordinary computational resources, which makes our formalism particularly promising to probe the nonlinear dynamics of quantum many-body systems that emerge from cumulant expansions.

physics.atom-ph↗