A Quanta é um grupo de pesquisa em Óptica e Informação Quântica da Universidade Federal de São Carlos (UFSCar).
Unimos pesquisa de ponta e exploramos os limites da interação entre luz e matéria no mundo quântico, transformando conceitos como superposição e emaranhamento em soluções inovadoras que conectam ciência de ponta à indústria e aos serviços.
Transformamos conhecimento científico em inovação estratégica, conectando a universidade à indústria e ao setor de serviços, e fortalecendo o protagonismo do Brasil no cenário global da tecnologia quântica.
Celso J. Villas-Boas, Carlos E. Máximo, Paulo J. Paulino, Romain P. Bachelard, Gerhard Rempe
Physical Review Letters134(13): 133603(2025)
Classical theory asserts that several electromagnetic waves cannot interact with matter if they interfere destructively to zero, whereas quantum mechanics predicts a nontrivial light-matter dynamics even when the average electric......
O. P. de Sá Neto, D. Z. Rossatto, Amjad Sohail, M. C. de Oliveira
Europhysics Letters153(1): 18001(2026)
The interaction between photons and phonons mediated by a third medium has significant potential for various applications in quantum information technology. Inspired by experimental investigations obtained on hybrid circuits, we......
In special relativity, particle trajectories, whether mass-bearing or not, can be traced on the Minkowski spacetime manifold in (3+1)D. Meantime, in quantum mechanics, trajectories in the phase space are not......
Tiago de Souza Farias, Gubio Gomes de Lima, Jonas Maziero, Celso Jorge Villas-Boas
(2025)
TL;DR
MixFunn, a novel neural network architecture designed to solve differential equations with enhanced precision, interpretability, and generalization capability, is introduced, demonstrating its effectiveness in achieving higher accuracy and improved generalization to regions outside the training domain relative to standard machine learning models.
Jaewon Lee, Charlie Stalker, Loris Colicchio, Fernando Redivo Cardoso, Jan Seelbinder, Sven Höfling, Christian Schneider, Celso J. Villas-Boas, Ana Predojević
Optics Express33(20): 41815(2025)
The visibility of two-photon interference is limited by the indistinguishability of the photons. In the cascaded emission of a three-level system, such as a single quantum dot, the indistinguishability of......
Bright and Dark States of Light: The Quantum Origin of Classical Interference.
Physical Review Letters134 (13) (2025)
Resumo
Classical theory asserts that several electromagnetic waves cannot interact with matter if they interfere destructively to zero, whereas quantum mechanics predicts a nontrivial light-matter dynamics even when the average electric field vanishes. Here, we show that in quantum optics, classical interference emerges from collective bright and dark states of light, i.e., particular cases of two-mode binomial states, which are entangled superpositions of multimode photon-number states. This makes it possible to explain wave interference using the particle description of light and the superposition principle for linear systems only. It also sheds new light on an old debate concerning the origin of complementarity.
Exploring the nature of phonon-qubit-photon coupling in a hybrid circuit
Europhysics Letters153 (1) 18001 (2026)
Resumo
The interaction between photons and phonons mediated by a third medium has significant potential for various applications in quantum information technology. Inspired by experimental investigations obtained on hybrid circuits, we aimed to develop a comprehensive theory for analytically calculating the transmission and reflection spectra, as well as obtaining eigenenergies of the circuits associated with this interaction. When analyzing the transmission spectra, we observed an intriguing correlation between the eigenenergies and the spectral peaks. This observation suggests the possibility of a deeper understanding of the stationary states involved in this unique hybrid circuit. Through this analysis, we aim not only to describe the observed phenomena but also to provide valuable insights for quantum technology.
Disentanglement of a Bipartite System Portrayed in a (3+1)D Compact Minkowski Manifold: Quadridistances and Quadrispeeds
Physics7 (4) 45 (2025)
Resumo
In special relativity, particle trajectories, whether mass-bearing or not, can be traced on the Minkowski spacetime manifold in (3+1)D. Meantime, in quantum mechanics, trajectories in the phase space are not strictly outlined because coordinate and linear momentum cannot be measured simultaneously with arbitrary precision since they do not commute within the Hilbert space formalism. However, from the density matrix representing a quantum system, the extracted information still produces an imperative description of its properties and, furthermore, by appropriately reordering the matrix entries, additional information can be obtained from the same content. Adhering to this line of work, the paper investigates the definition and the meaning of velocity and speed in a typical quantum phenomenon, the disentanglement for a bipartite system when dynamical evolution is displayed in a (3+1)D pseudo-spacetime whose coordinates are constructed from combinations of entries to the density matrix. The formalism is based on the definition of a Minkowski manifold with compact support, where trajectories are defined following the same reasoning and formalism present in the Minkowski manifold of special relativity. The space-like and time-like regions acquire different significations referred to entangled-like and separable-like, respectively. The definition and the sense of speed and velocities of disentanglement follow naturally from the formalism. Depending on the dynamics of the physical state of the system, trajectories may meander between regions of entanglement and separability in the space of new coordinates defined on the Minkowski manifold.
Mixfunn: A Neural Network for Differential Equations with Improved Generalization and Interpretability
(2025)
Resumo
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.
Extraction of coherence times of biexciton and exciton photons emitted by a single resonantly excited quantum dot under controlled dephasing.
Optics Express33 (20) 41815 (2025)
Resumo
The visibility of two-photon interference is limited by the indistinguishability of the photons. In the cascaded emission of a three-level system, such as a single quantum dot, the indistinguishability of each photon in the pair is primarily affected by two main factors: the temporal correlation between paired photons and dephasing. Investigating the individual effects of these factors on photon indistinguishability is challenging, as both factors affect it simultaneously. In this study, we investigate the temperature-dependent two-photon interference visibility of the biexciton and exciton photons emitted from a single quantum dot under two-photon resonant excitation, while keeping the temporal correlation between the paired photons intact. Finally, we simultaneously extract the coherence times of the biexciton and exciton photons as a function of temperature.
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