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Autor Luis Aina, Alfredo |
Documentos disponibles escritos por este autor (102)
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We examine weak measurements of arbitrary observables where the object is prepared in a mixed state and on which measurements with imperfect detectors are made. The weak value of an observable can be expressed as a conditional expectation value [...]![]()
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We derive exceedingly simple practical procedures revealing the quantum nature of states and measurements by the violation of classical upper bounds on the statistics of arbitrary measurements. Data analysis is minimum, and definite conclusions [...]![]()
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We derive simple practical tests revealing the quantum nature of states by the violation of classical upper bounds on the statistics of multiple outcomes of an observable. These criteria can be expressed in terms of the Kullback-Leibler divergen[...]![]()
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We examine the performance of a nonlinear fiber gyroscope for improved signal detection beating the quantum limits of its linear counterparts. The performance is examined when the nonlinear gyroscope is illuminated by practical field states, suc[...]![]()
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We examine quantum detection via a Michelson interferometer embedded in a gas with Kerr nonlinearity. This nonlinear interferometer is illuminated by pulses of classical light. This strategy combines the robustness against practical imperfection[...]![]()
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Bermúdez, A. ; Martín Delgado, Miguel Ángel ; Luis Aina, Alfredo | American Physical Society | 2008-03-18We study the nonrelativistic limit of a paradigmatic model in relativistic quantum mechanics, the two-dimensional Dirac oscillator. Remarkably, we find a different kind of Zitterbewegung which persists in this nonrelativistic regime, and leads t[...]![]()
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Fadel, Matteo ; Ares Santos, Laura ; Luis Aina, Alfredo ; He, Qiongyi | American Physical Society | 2020-05-22We use the uncertainty relation between the operators associated with the total number of particles and with the relative phase of two bosonic modes to construct entanglement and Einstein-Podolsky-Rosen steering criteria. These can be tested exp[...]![]()
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We examine a case study where classical evolution emerges when observing a quantum evolution. By using a single-mode quantum Kerr evolution interrupted by measurement of the double-homodyne kind (projecting the evolved field state into classical[...]![]()
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We present a fully operational and consistent approach to complementarity. In contrast to previous approaches, in this proposal the duality relations emerge exclusively from the outcomes of simultaneous measurements performed on every run of the[...]![]()
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The problem of a correct quantum description of the phase difference is examined from the perspective of parameter estimation theory. It is shown that an optimum phase-shift measurement defines a phase difference operator which coincides with ot[...]![]()
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We address a systematic approach to the study of the optimum states reaching maximum resolution for interferometers with moving mirrors. We find a correspondence between the optimum states for interferometers with fixed and moving mirrors.![]()
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We introduce a unitary operator representing the exponential of the phase difference between two modes of the electromagnetic field. The eigenvalue spectrum has a discrete character that is fully analyzed. We relate this operator with a suitable[...]![]()
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The quantum theory of light propagation in a Kerr medium is applied to describe changes in the polarization state of light. A number of purely quantum effects arising during the propagation are analyzed. Stokes operators and Pegg-Barnett formali[...]![]()
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We propose a practical arrangement that allows one to reach the Heisenberg limit in precision phase-shift measurements. This is achieved via phase-shift amplification. The arrangement we propose is based on experimental processes already carried[...]![]()
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We analyze the relation between the classical part of quantum observables and the distributions representing quantum states and observables on the classical phase space. We determine in which conditions such a relation can be established, and th[...]![]()
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We introduce a probability distribution for polarization of three-dimensional quantum light fields as a marginal of the quadrature Q function for a three-mode field by removing the variables irrelevant for polarization (total intensity and globa[...]![]()
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We propose a formal resource-theoretic approach to quantify the degree of polarization of two- and three-dimensional random electromagnetic fields. This endows the space of spectral polarization matrices with the orders induced by majorization o[...]![]()
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We elucidate a ray picture of coherence for vectorial electromagnetic waves by using the Stokes parameters for light rays defined by the optical Wigner function. Paraxial propagation is formulated as a complementary Huygens principle. We show th[...]![]()
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We formulate polarization uncertainty relations and polarization squeezing criteria in a SU(2) invariant manner. In this formulation the SU(2) coherent states are the only minimum uncertainty states. We show that polarization squeezing is a nonc[...]![]()
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We examine whether the Stokes parameters of a two-mode electromagnetic field results from the superposition of the spins of the photons it contains. To this end we express any n-photon state as the result of the action on the vacuum of n creatio[...]![]()
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Porras, Miguel A. ; Gonzalo Fonrodona, Isabel ; Luis Aina, Alfredo | American Physical Society | 2016-04-07We show that quantum Zeno dynamics can be mimicked by the isolated evolution of an unobserved system in an effective potential. Monitoring frequently whether a particle remains in a region of space leads to the same wave-packet dynamics as placi[...]![]()
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We develop practical schemes for the measurement of the covariance matrix for intrinsic angular-momentum variables in quantum optics. We particularize this approach to two-beam polarimetry and interferometry, as well as to ensembles of two-level[...]![]()
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We examine whether metrological resolution beyond coherent states is a nonclassical effect. We show that this is true for linear detection schemes but false for nonlinear schemes, and propose a very simple experimental setup to test it. We find [...]![]()
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In this work we analyze the quantum phase properties of pairs of electromagnetic field modes. Since phases differing by 2? are physically indistinguishable, we propose a general procedure to obtain the correct mod(2?) probability distributions f[...]![]()
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We investigate duality relations between conjugate observables after measurements performed on a single realization of the system. The application of standard inference methods implies the existence of duality relations for single systems when u[...]![]()
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We develop a thorough connection between visibility, coherence, and phase statistics for N-dimensional quantum systems and N classical waves.![]()
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We show the formal equivalence between the phase-space representations of transformations and quantum states. We study invariant quantum input-output transformations in phase space and in Hilbert space. We show that all invariant processes are l[...]![]()
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We examine the relationship between nonseparable transformations and nonlinear optical processes, surpassing the Heisenberg limit in precision measurements.![]()
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We introduce quantum states associated with single phase space points in the Wigner formalism for finite-dimensional spaces. We consider both continuous and discrete Wigner functions. This analysis provides a procedure for a direct practical obs[...]![]()
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We derive quantum polarization distributions on the Poincare sphere for two-mode fields as suitable marginals of the standard s-ordered quadrature distributions that include the Wigner function. We compare them with previously introduced distrib[...]![]()
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We study the polarization properties of three-dimensional quantum light fields by using the Stokes operators. We modify the standard definition of degree of polarization in order to encompass polarization properties in the quantum domain. We sho[...]![]()
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The use of Rényi entropy as an uncertainty measure alternative to variance leads to the study of states with quantum fluctuations below the levels established by Gaussian states, which are the position-momentum minimum uncertainty states accordi[...]![]()
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We present different schemes for preparing and maintaining the quantum state of multilevel systems. This is achieved via a suitable combination of coherent trapping and the Zeno effect which serves to protect the prepared state against undesired[...]![]()
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We demonstrate the possibility of practical tomographic determination of arbitrary input-output transformations. It is shown that the Liouville-space formalism provides a generalization of standard tomography encompassing the reconstruction of p[...]![]()
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Porras, Miguel A. ; Luis Aina, Alfredo ; Gonzalo Fonrodona, Isabel | American Physical Society | 2014Although the quantum Zeno effect takes its name from Zeno’s arrow paradox, the effect of frequently observing the position of a freely moving particle on its motion has not been analyzed in detail in the frame of standard quantum mechanics. We s[...]![]()
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The question of the representation of quantum stationary partially polarized waves as random superpositions of different polarization ellipses is addressed. To this end, the Bohmian formulation of quantum mechanics is considered and extended to [...]![]()
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Several quantum descriptions of the relative phase between an atomic dipole and a one-mode electromagnetic field are examined. Positive-operator measures for this variable are derived from dipole and field-phase formalisms. They are analyzed and[...]![]()
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In response to the objection raised by Pegg and Vaccaro [the preceding Comment] we point out that their example is not a difhculty in directly representing the phase difference by the ?12 operator. In fact, we argue that it is a property common[...]![]()
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We propose a formal resource-theoretic approach to assess the coherence between partially polarized electromagnetic fields. From this framework, we identify two resource theories for the vectorial coherence: polarization-sensitive coherence and [...]![]()
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We show that there are extremely simple signal detection schemes where the finiteness of energy resources places no limit on the resolution. On the contrary, larger resolution can be obtained with lower energy. To this end the generator of the s[...]![]()
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We address the propagation of the spin along classical trajectories for a spin-1/2 particle obeying the Dirac equation with scalar potentials. Focusing on classical trajectories as the exact propagation of wave-function discontinuities, we find [...]![]()
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The states generated from the vacuum in two parametric down-conversion crystals with aligned idler beams are studied. It is shown that after a measurement of the photon number in some of the modes, the emerging states can be related to SU(2) and[...]![]()
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We develop an SU(2)-invariant approach to the depolarization of quantum systems as the effect of random unitary SU(2) transformations. From it we derive an SU(2)-invariant Markovian master equation. This is applied to several quantum states exam[...]![]()
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We provide evidence that the uncertainty in detection of small and deterministic phase-shift deviations from a working point can be lower than the Heisenberg bound, for a fixed finite mean number of photons. We achieve that by exploiting nonline[...]![]()
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Weak-measurement-based experiments (Kocsis et al., 2011) have shown that, at least for pure states, the average evolution of independent photons in Young's two-slit experiment is in compliance with the trajectories prescribed by the Bohmian form[...]![]()
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We present a simple multimode analysis of the Zeno and anti-Zeno effects in spontaneous parametric down-conversion. In this process the input vacuum is an unstable state decaying into a reservoir of down-converted modes by emitting a pair of pho[...]![]()
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We examine the appearance of Zeno and anti-Zeno effects when the unitary evolution of a two-level system is observed. We demonstrate that, contrary to previous claims, the anti-Zeno effect can occur in two-level systems so that the observation c[...]![]()
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Porras, Miguel A. ; Luis Aina, Alfredo ; Gonzalo Fonrodona, Isabel ; Sanz, Ángel S. | American Physical Society | 2011-11-14We analyze a simple and feasible practical scheme displaying Zeno, anti-Zeno, and inverse-Zeno effects in the observation of wave-packet spreading caused by free evolution. The scheme is valid both in spatial diffraction of classical optical wav[...]![]()
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Luis Aina, Alfredo ; Gonzalo Fonrodona, Isabel ; Porras, Miguel A. | American Physical Society | 2013-06-20We describe a version of the Zeno effect where the monitored physical property cannot be represented by a standard operator in the system space and the evolution to be prevented by observation is not unitary. This is the case of quantum-state pu[...]![]()
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Two examples are presented where the photon emission on spontaneous parametric down-conversion is prevented when attempts are made to infer the moment of emission. This inhibition is analyzed in terms of the disturbance caused on the system by t[...]