Bertúlio de Lima Bernardo

Data transmission by hypergeometric modes through a hyperbolic-index medium

We study the existence of a novel complete family of exact and orthogonal solutions of the paraxial wave equation. The complex amplitude of these beams is proportional to the confluent hypergeometric function, which we name hypergeometric modes of type-II (HyG-II). It is formally demonstrated that hyperbolic-index medium can generate and support the propagation of such a class of beams. Since these modes are eigenfunctions of the photon orbital angular momentum, we conclude that an optical fiber with hyperbolic-index profile could take advantage over other graded-index fibers by the capacity of data transmission.

Time Correlation and Decoherence in a Two-Particle Interferometer

A two-particle interferometer is theoretically analyzed to show how decoherence induced by interactions with the environment affects time correlations, a process we call time correlation decoherence. Specifically, on the basis of simple mathematical analysis, we show how the interaction between a bipartite entangled system and a photon bath representing the environment can efface the oscillations in the coincidence detection rate of the interferometer. We discuss the dependence of this kind of decoherence on the photon energy and density.A two-particle interferometer is theoretically analyzed to show how decoherence induced by interactions with the environment affects time correlations, a process we call time correlation decoherence. Specifically, on the basis of simple mathematical analysis, we show how the interaction between a bipartite entangled system and a photon bath representing the environment can efface the oscillations in the coincidence detection rate of the interferometer. We discuss the dependence of this kind of decoherence on the photon energy and density.

Theoretical study on stability of hybrid bilayers

Motivated by the recent experimental realization of the hybrid nanostructure of graphene and boron nitride (h-BN) sheet, and studies of gap modulation by strain, we use first principles calculations based on density functional theory to investigate the effects of strain in hybrid bilayers composed of two monolayers of graphene with a nanodomain of . The calculations were made with two different approximations for the functional exchange-correlation, GGA and VDW-DF. We investigate the modification in the electronic structure and structural properties of various configurations of the hybrid bilayers. Among the configurations, those with Bernal stacking are found to be more stable when compared to the others. Studies of the compressive strain influence were made only in the structure that has been shown to be the most stable. We have found that the two approximations used in the calculations exhibit the same results for the electronic properties of all structures. The opening of the energy gap due to strain was possible in the calculations by using the GGA approximation, but the same does not happen in the calculations using the VDW-DF approximation. Our analysis shows that the VDW-DF approximation is better suited for studies involving surfaces.

How a single particle simultaneously modifies the physical reality of two distant others: a quantum nonlocality and weak value study

The concept of wave-particle duality, which is a key element of quantum theory, has been remarkably found to manifest itself in several experimental realizations as in the famous double-slit experiment. In this specific case, a single particle seems to travel through two separated slits simultaneously. Nevertheless, it is never possible to measure it in both slits, which naturally appears as a manifestation of the collapse postulate. In this respect, one could as well ask if it is possible to “perceive” the presence of the particle at the two slits simultaneously, once its collapse could be avoided. In this article, we use the recently proposed entanglement mediation protocol to provide a positive answer to this question. It is shown that a photon which behaves like a wave, i.e., which seems to be present in two distant locations at the same time, can modify two existing physical realities in these locations. Calculations of the “weak trace” left by such photon also enforce the validity of the present argumentation.

Signal enhancement of magneto-optical Kerr effect measurements by weak value amplification

Abstract Magneto-optic effects are widely applied in the analysis of magnetic thin films. Specifically, due to its local probing characteristic, sensitivity, and experimental simplicity, the surface magneto-optic Kerr effect has been shown to be very useful in the investigation of the magnetization structure of materials. In this work, we propose a weak measurement-based protocol to enhance the pointer deflection, namely the polarization rotation of an incident light beam upon reflection from a magnetic surface, in some orders of magnitude, without loss in precision. It could provide a new insight into magnetic research.

Photon statistics as a probe for weak measurements

We propose a framework to perform weak measurements in which photon statistics is employed as the measuring device. Specifically, we show that when a coherent state is utilized as the probe, as a result, a super-Poissonian statistics is obtained whose average number of photons and variance are strongly dependent on the weak effect that takes place in the interim between pre- and post-selection. These results shed new light on the study of weak measurements in what concerns the sensibility of the measurer.

Drag Force Experienced by a Body Moving through a Rarefied Gas

Understanding how the drag force acts on a body is important in many areas of science and technology, and substantial efforts have been made to evaluate this force with high precision, particularly in the realm of fluid mechanics. In this paper we introduce a simple model based on kinetic theory that allows us to estimate the drag force on a body moving through a rarefied gas, where the assumptions of fluid mechanics no longer apply. Despite the simplicity of this model, the results agree quite well with the exact solutions. However, the simplicity of the model allows it to be used with undergraduate students in an introductory course.