Examinando por Autor "Valido, Antonio A"

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Approximating vibronic spectroscopy with imperfect quantum optics
(IOP Publishing, 2018-11-23) Valido, Antonio A; Clements, William R; Renema, Jelmer J; Eckstein, Andreas; Lita, Adriana; Gerrits, Thomas; Woo Nam, Soo; Kolthammer, W Steven; Huh, Joonshuk; Walmsley, Iam A
We study the impact of experimental imperfections on a recently proposed protocol for performing quantum simulations of vibronic spectroscopy. Specifically, we propose a method for quantifying the impact of these imperfections, optimizing an experiment to account for them, and benchmarking the results against a classical simulation method. We illustrate our findings using a proof of principle experimental simulation of part of the vibronic spectrum of tropolone. Our findings will inform the design of future experiments aiming to simulate the spectra of large molecules beyond the reach of current classical computers.
Asymptotic discord and entanglement of nonresonant harmonic oscillators under weak and strong dissipation
(American Physical Society, 2012-07-20) Valido, Antonio A; Alonso, Daniel; Correa, Luis A
In this work, we calculate the exact asymptotic quantum correlations between two interacting nonresonant harmonic oscillators in a common Ohmic bath. We derive analytical formulas for the covariances, fully describing any Gaussian stationary state of the system, and use them to study discord and entanglement in the strong- and weak-dissipation regimes. We discuss the rich structure of the discord of the stationary separable states arising in the strong-dissipation regime. Also under strong dissipation, when the modes are not mechanically coupled, these may entangle only through their interaction with the common environment. Interestingly enough, this stationary entanglement assisted by dissipation is only present within a finite band of frequencies and increases with the dissipation rate. Robust entanglement between detuned oscillators is also observed at low temperature.
Gaussian entanglement induced by an extended thermal environment
(American Physical Society, 2013-10-03) Valido, Antonio A; Alonso, Daniel; Kohler, Sigmund
We study stationary entanglement between three harmonic oscillators which are dipole coupled to a one-dimensional or a three-dimensional bosonic environment. The analysis of the open-system dynamics is performed with generalized quantum Langevin equations which we solve exactly in a Fourier representation. The focus lies on Gaussian bipartite and tripartite entanglement induced by the highly non-Markovian interaction mediated by the environment. This environment-induced interaction represents an effective many-party interaction with a spatial long-range feature: A main finding is that the presence of a passive oscillator is detrimental for stationary two-mode entanglement. Furthermore, our results indicate that the environment-induced entanglement mechanism corresponds to uncontrolled feedback which is predominantly coherent at low temperatures and for moderate oscillator-environment coupling as compared to the oscillator frequency.
Gaussian phase sensitivity of boson-sampling-inspired strategies
(American Physical Society, 2021-03-24) Valido, Antonio A; García-Ripoll, Juan José
In this paper we study the phase sensitivity of generic linear interferometric schemes using Gaussian resources and measurements. Our formalism is based on the Fisher information. This allows us to separate the contributions of the measurement scheme, the experimental imperfections, and auxiliary systems. We demonstrate the strength of this formalism using a broad class of multimode Gaussian states that includes well-known results from single- and two-mode metrology scenarios. Using this, we prove that input coherent states or squeezing improve upon the nonclassical states proposed in preceding boson-sampling-inspired phase-estimation schemes. We also develop a polychromatic interferometric protocol, demonstrating an enhanced sensitivity with respect to two-mode squeezed-vacuum states, for which the ideal homodyne detection is formally shown to be optimal.
Gaussian tripartite entanglement out of equilibrium
(American Physical Society, 2013-07-11) Valido, Antonio A; Alonso, Daniel; Correa, Luis A
The stationary multipartite entanglement between three interacting harmonic oscillators subjected to decoherence is analyzed in the largely unexplored nonequilibrium strong dissipation regime. We compute the exact asymptotic Gaussian state of the system and elucidate its separability properties, qualitatively assessing the regions of the space of parameters in which fully inseparable states are generated. Interestingly, the sharing structure of bipartite entanglement is seen to degrade as dissipation increases even for very low temperatures, at which the system approaches its ground state. We also find that establishing stationary energy currents across the harmonic chain does not correspond with the buildup of biseparable steady states, which relates instead just to the relative intensity of thermal fluctuations.
Hierarchies of multipartite entanglement for continuous-variable states
(Physical Review A, 2014-11-14) Valido, Antonio A; Mintert, Florian; Levi, Federico
We derive a hierarchy of separability criteria for multimode continuous-variable systems. They permit one to study in a unified way the k-partite entanglement of broad classes of Gaussian and non-Gaussian states. With specific examples we demonstrate the strength of the criteria, and we discuss their assessment based on data obtained from Gaussian measurements.
Quantum correlations and energy currents across three dissipative oscillators
(American Physical Society, 2015-06-18) Valido, Antonio A; Alonso, Daniel; Ruiz, Antonia
We present a study that addresses both the stationary properties of the energy current and quantum correlations in a three-mode chain subjected to Ohmic and super-Ohmic dissipations. An extensive numerical analysis shows that the mean value and the fluctuations of the energy current remain insensitive to the emergence of a rich variety of quantum correlations, such as two-mode discord and entanglement and bipartite three-mode and genuine tripartite entanglement. The discussion of the numerical results is based on the derived expressions for the stationary properties in terms of the two-time correlation functions of the oscillator operators, which carry the quantum correlations. Interestingly, we show that quantum discord can be enhanced by considering both initially squeezed thermal bath states and imposing temperature gradients.
Quantum kinetic theory of flux-carrying Brownian particles
(IOP Publishing, 2022-07-15) Valido, Antonio A
We develop the kinetic theory of the flux-carrying Brownian motion recently introduced in the context of open quantum systems. This model constitutes an effective description of two-dimensional dissipative particles violating both time-reversal and parity that is consistent with standard thermodynamics. By making use of an appropriate Breit–Wigner approximation, we derive the general form of its quantum kinetic equation for weak system-environment coupling. This encompasses the well-known Kramers equation of conventional Brownian motion as a particular instance. The influence of the underlying chiral symmetry is essentially twofold: the anomalous diffusive tensor picks up antisymmetric components, and the drift term has an additional contribution which plays the role of an environmental torque acting upon the system particles. These yield an unconventional fluid dynamics that is absent in the standard (two-dimensional) Brownian motion subject to an external magnetic field or an active torque. For instance, the quantum single-particle system displays a dissipationless vortex flow in sharp contrast with ordinary diffusive fluids. We also provide preliminary results concerning the relevant hydrodynamics quantities, including the fluid vorticity and the vorticity flux, for the dilute scenario near thermal equilibrium. In particular, the flux-carrying effects manifest as vorticity sources in the Kelvin's circulation equation. Conversely, the energy kinetic density remains unchanged and the usual Boyle's law is recovered up to a reformulation of the kinetic temperature.
Tensor network states in time-bin quantum optics
(American Physical Society, 2018-06-05) Valido, Antonio A; Renema, Jelmer J; Walmsley, Ian A; Kolthammer, W Steven; Lubasch, Michael; Jaksch, Dieter; García-Patrón, Raúl
The current shift in the quantum optics community towards experiments with many modes and photons necessitates new classical simulation techniques that efficiently encode many-body quantum correlations and go beyond the usual phase-space formulation. To address this pressing demand we formulate linear quantum optics in the language of tensor network states. We extensively analyze the quantum and classical correlations of time-bin interference in a single fiber loop. We then generalize our results to more complex time-bin quantum setups and identify different classes of architectures for high-complexity and low-overhead boson sampling experiments.
Topological Magnetoelectric Response in Passive Magnetic Devices
(Physical Review Applied, 2023-09-15) Valido, Antonio A; Castro, Alejandro J.
Despite the prospect of next-generation electronic technologies spurring the investigation of the remarkable topological magnetoelectric response, its potential remains largely unexplored in the application of basic electronic devices. In this paper, we undertake this task at the theoretical level by addressing the θ-electrodynamics and examine electromagnetic properties (e.g., tunable inductance, operating frequency range, and power consumption) of three fundamental passive magnetic devices endowed with this effect: the primitive transformer, the bilayer solenoid inductor, and the solenoid actuator. We further exploit the methodology of magnetic circuits to obtain an extended Hopkinson’s law that is valid for both topological and ordinary magnetoelectric responses (provided it is uniform in the bulk). Under low-power conditions, we find out that the functionally passive part of the topological-magnetoelectric transformer, the solenoid inductor as well as the solenoid actuator, is indistinguishable from the conventional situation up to second order in the magnetoelectric susceptibility; we argue that the main benefit of using topological insulators essentially relies on a lower power consumption. Our theoretical framework is also convenient to analyze magnetoelectric inductors endowed with a relatively large magnetoelectric susceptibility, they display a broad inductance tunability of over 200% up to 100 GHz in the millimeter length scale. Conversely, our treatment predicts that the operating frequency range could be restricted below the ultralow frequency by a significantly strong magnetoelectric response (e.g., retrieved by certain multiferroic heterostructures).