Información del autor
Autor Luis Aina, Alfredo |
Documentos disponibles escritos por este autor (102)
texto impreso
An alternative derivation of the Pegg-Barnett phase operator is presented. This approach is based on the properties of the representation in quantum mechanics of a nonlinear nonbijective canonical transformation. It does not use as its starting [...]texto impreso
We examine a family of intrinsic performance measures in terms of probability distributions that generalize Hellinger distance and Fisher information. They are applied to quantum metrology to assess the uncertainty in the detection of minute cha[...]texto impreso
We derive simple practical procedures revealing the quantum behavior of angular momentum variables by the violation of classical upper bounds on the statistics. Data analysis is minimum and definite conclusions are obtained without evaluation of[...]texto impreso
Two examples are presented where the observation of the emission in parametric down-conversion leads to its enhancement instead of its inhibition. The improvement is analyzed in terms of the quantum features of the observation.texto impreso
Any nonclassical effect noticed in measured statistics is usually attributed just to the light state being observed. According to Born's rule, quantum probabilities are given by the overlap between the system state and measurement states in a qu[...]texto impreso
We analyze the performance of nonlinear detection schemes surpassing the Heisenberg limit with semiclassical input states when using realistic detectors having nonunit detection efficiency.texto impreso
We provide a very simple case showing that the weak form of the Heisenberg limit can be beaten while the prior information is improved without bias.texto impreso
The well-known difficulties of defining a phase operator of an oscillator are considered from the point of view of the canonical transformation to action and phase-angle variables. This transformation turns out to be nonbijective, i.e., it is no[...]texto impreso
We elaborate an approach to quantum fluctuations of angular momentum based on the diagonalization of the covariance matrix in two versions: real symmetric and complex Hermitian. At difference with previous approaches this is SU(2) invariant and [...]texto impreso
Bermúdez, A. ; Martín-Delgado Alcántara, Miguel Ángel ; Luis Aina, Alfredo | American Physical Society | 2008-06-11We study a relativistic spin-1/2 fermion subjected to a Dirac oscillator coupling and a constant magnetic field. An interplay between opposed chirality interactions culminates in the appearance of a relativistic quantum phase transition, which c[...]texto impreso
Two complementary observables can be measured simultaneously so that the exact individual distributions can be recovered by a proper data inversion. We apply this program to the paradigmatic example of the Young interferometer from the classical[...]texto impreso
We compare the maximum achievable polarization correlations for classical-like separable states and quantum entangled states. For one-photon systems we find that the maximally entangled states have three times larger correlations than the maximu[...]texto impreso
Geometrical optics can be regarded both as the short-wavelength approximation of the propagation of electromagnetic waves, and as the exact way in which propagate the surfaces of discontinuity of the classical electromagnetic field. In this work[...]texto impreso
Porras, Miguel A. ; Luis Aina, Alfredo ; Gonzalo Fonrodona, Isabel | American Physical Society | 2013-11-04We provide theoretical and experimental evidence of a classical-optics realization of quantum Zeno dynamics. In contrast to other approaches, the classical implementation is extremely simple and adaptable. Frequently monitoring the transverse sp[...]texto impreso
Two-path interference of transversal vectorial waves is embedded within a larger scheme: this is four-path interference between four scalar waves. This comprises previous approaches to coherence between vectorial waves and restores the equivalen[...]texto impreso
We examine the relation between second-order coherence and resolution in the interferometric detection of phase shifts. While for classical thermal light resolution and second-order coherence are synonymous, we show that for quantum light beams [...]texto impreso
texto impreso
Very simple duality relations-assessing complementarity for two-dimensional systems are obtained by introducing a measure of fluctuations derived from dispersion. These relations fully explain the enforcement of complementarity in situations in [...]texto impreso
We generalize to systems with arbitrary finite dimension a measure of quantum fluctuations (the certainty) previously introduced for two-dimensional systems. Using this measure, we study the duality relations satisfied by complementary observabl[...]texto impreso
Quantum phase difference is used to analyze which-path detectors in which the loss of interference predicted by complementarity cannot be attributed to classical momentum transfer between the interfering particle and the measuring apparatus. It [...]texto impreso
We examine basic properties of complementarity by using the most general description of quantum observables as positive-operator measures. We show that, in general, two observables can be complementary or not depending on the measure of fluctuat[...]texto impreso
We examine two simple and feasible practical schemes allowing the complete determination of any quantum measuring arrangement. This is illustrated with the example of parity measurement.texto impreso
We show that variance and Shannon entropy provide contradictory conclusions for the uncertainty associated with the number operator for some families of states of harmonic oscillator systems with fixed mean number, and for the uncertainty of a s[...]texto impreso
We assess the degree of coherence of vectorial electromagnetic fields in the space-frequency domain as the distance between the cross-spectral density matrix and the identity matrix representing completely incoherent light. This definition is co[...]texto impreso
Quantum optics entails polarization properties that cannot be fully described by the classical Stokes parameters. In this work, we characterize the polarization of classical as well as quantum fields by means of a probability distribution on the[...]texto impreso
We address a quantitative determination of the degree of polarization of type-II unpolarized light via the computation of the distance between the polarization distribution and the uniform distribution associated with fully unpolarized light (i.[...]texto impreso
We present an intuitive model of detector self-tomography. Two identical realizations of the detector are illuminated by an entangled state that connects the joint statistics in a way in which each detector sees the other as a kind of mirror ref[...]texto impreso
We find the observables that-can be determined by two practical schemes based on atom-field resonant interaction. In the first example, the interaction is followed by photon-number and atomic-population measurements. In the second scheme the dir[...]texto impreso
A full quantum analysis of 100% efficient interaction-free measurements is presented. It is shown that it is possible to describe consistently the phenomenon in terms of an effective interaction between object and apparatus that disturbs measura[...]texto impreso
We examine the evolution of a two-level atom when its population is monitored. The detection proposed is an interaction-fret measurement, so that the observation occurs without photon exchange between the atom and the apparatus. It is shown that[...]texto impreso
We show within a very simple framework that different measures of fluctuations lead to uncertainty relations resulting in contradictory conclusions. More specifically we focus on Tsallis and Renyi entropic uncertainty relations and we get that t[...]texto impreso
Ensemble approach to coherence between two scalar harmonic light vibrations and the phase difference
We develop an approach to coherence between two scalar harmonic light vibrations derived from the ensemble interpretation of statistical optics. Coherence is presented as a statistical variable itself that turns out to be the phase difference be[...]texto impreso
We compute Renyi entropies for the statistics of a noisy simultaneous observation of two complementary observables in two-dimensional quantum systems. The relative amount of uncertainty between two states depends on the uncertainty measure used.[...]texto impreso
We demonstrate that the superpositions of macroscopically distinct coherent states are maximally entangled states. Among other possible applications of this result, in this paper we show that the experimental arrangements generating superpositio[...]texto impreso
Martínez Matos, Óscar ; Alieva Krasheninnikova, Tatiana ; Canabal Boutureira, Héctor ; Navarrete Fernández, María de la Cruz ; Gonzalo Fonrodona, Isabel ; Herrera Fernández, José María ; Irigoyen Irigoyen, Maite ; Luis Aina, Alfredo ; Piquero Sanz, Gemma ; Rodrigo Martín Romo, José Augusto ; Sánchez Brea, Luis Miguel ; Sánchez Martín, José Antonio ; Serna Galán, Julio ; Tercero Gómez, José Luis ; Torcal Milla, Francisco José ; Vilas Prieto, José Luis ; Weigand Talavera, Rosa | 2015Se propone un cambio en la metodología docente de la asignatura Laboratorio de Física III del Grado en Física, para hacerla más dinámica y potenciar la participación e iniciativas de los estudiantes, adecuándola al espíritu de Boloniatexto impreso
We show that metrological resolution in the detection of small phase shifts provides a suitable generalization of the degrees of coherence and polarization. Resolution is estimated via Fisher information. Besides the standard two-beam Gaussian c[...]texto impreso
We propose a simple method to generate in practice the most general two-mode states with maximum entanglement. The method is based on energy-conserving dispersive interactions that can be easily implemented in different context such as quantum o[...]texto impreso
We analyze the quantum limit to the sensitivity of the detection of small displacements. We focus on the case of free particles and harmonic oscillators as the systems experiencing the displacement. We show that the minimum displacement detectab[...]texto impreso
We show that a single experiment can test simultaneously and independently both the nonclassicality of states and of measurements by the violation or fulfillment of classical bounds on the statistics. Nonideal measurements affected by imperfecti[...]texto impreso
We elaborate on a Hilbert-Schmidt distance measure assessing the intrinsic metrological accuracy in the detection of signals imprinted on quantum probe states by signal-dependent transformations. For small signals this leads to a probe-transform[...]texto impreso
We estimate the quantum state of a system between two measurements via a maximum likelihood strategy. This incorporates all the information provided by preselection and postselection in a legitimate quantum state. Moreover, it allows to include [...]texto impreso
We study the performance of linear and nonlinear optical schemes for the detection of weak signals for two classes of probe states. These are quadrature coherent squeezed states and the minimum uncertainty states of the generator of the transfor[...]texto impreso
A multimode quantum analysis of noise reduction in interferometric measurements is presented. A unitary transformation relating the output modes with the input ones for a Michelson interferometer with moving mirrors is given. The evaluation of t[...]texto impreso
Derivation and experimental violation of Bell-like inequalities involve the measurement of incompatible observables. Simple complementarity forbids the existence of such joint probability distribution. Moreover, the measurement of incompatible o[...]texto impreso
Nonclassicality cannot be a single-observable property, since the statistics of any quantum observable is compatible with classical physics. We develop a general procedure to reveal nonclassical behavior of light states from the joint statistics[...]texto impreso
Quantum polarization is investigated by means of a trajectory picture based on the Bohmian formulation of quantum mechanics. Relevant examples of classical-like two-mode field states are thus examined, namely, Glauber and SU(2) coherent states. [...]texto impreso
We study nonclassical polarization states characterized by polarization distributions taking negative values. We consider two different families of polarization distributions that include polarization analogs of the Wigner function. We apply dif[...]texto impreso
We derive upper bounds on the statistics of phase and phase difference that are satisfied by all classical states. They are obtained by finding the maximum projection of classical states on phase states. For a single-mode phase, meaningful bound[...]texto impreso
We show that there are nonclassical states with lesser joint fluctuations of phase and number than any classical state. This is rather paradoxical since one would expect classical coherent states to be always of minimum uncertainty. The same res[...]texto impreso
We study nonclassicality in the product of the probabilities of noncommuting observables. We show that within the quantum theory, nonclassical states can provide larger probability product than classical states, so that nonclassical states appro[...]