Conventional Brownian motion in harmonic systems has provided a deep understanding of a great diversity of dissipative phenomena. We address a rather fundamental microscopic description for the (linear) dissipative dynamics of two-dimensional harmonic oscillators that contains the conventional Brownian motion as a particular instance. This description is derived from first principles in the framework of the so-called Maxwell-Chern-Simons electrodynamics, or also known, Abelian topological massive gauge theory. Disregarding backreaction effects and endowing the system Hamiltonian with a suitable renormalized potential interaction, the conceived description is equivalent to a minimal-coupling theory with a gauge field giving rise to a fluctuating force that mimics the Lorentz force induced by a particle-attached magnetic flux. We show that the underlying symmetry structure of the theory (i.e. time-reverse asymmetry and parity violation) yields an interacting vortex-like Brownian dynamics for the system particles. An explicit comparison to the conventional Brownian motion in the quantum Markovian limit reveals that the proposed description represents a second-order correction to the well-known damped harmonic oscillator, which manifests that there may be dissipative phenomena intrinsic to the dimensionality of the interesting system.

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.Contribution of NIST, an agency of the U.S. government, not subject to copyright. arXiv:1710.08655v3 [quant-ph]

In this work, we calculate the exact asymptotic quantum correlations between two interacting non-resonant 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 is only present within a finite band of frequencies and increases with the dissipation rate. In addition, robust entanglement between detuned oscillators is observed at low temperature.Over the last decades, non-classical correlations such as discord and entanglement have been widely acknowledged to play a central role in quantum mechanics. In particular, the robustness of entanglement against decoherence in continuous-variable (CV) systems has been object of study in a number of recent publications [1-10]. Due to the fact that entanglement is a valuable resource in quantum communication and information processing with CV, the investigation of the conditions under which bipartite states indefinitely preserve their non-separable nature in presence of noise and dissipation is not only of fundamental importance, but also of practical interest.Gaussian two-mode states occupy a priviledged position among all entangled CV preparations, since they combine easy experimental realization (e.g. the output beams in an optical parametric oscillator), with simple mathematical description in terms of their second order moments, which are experimentally determined via homodyne detection [11]. These CV systems also find physical realization in mechanical oscillators, such as trapped ions coupled by their electrostatic interaction [12]. A simple but rather general model describing those systems consists of two coupled detuned harmonic oscillators, linearly interacting, and in contact with a bath.The stationary entanglement of two resonant modes in a squeezed state under decoherence was studied in Refs. [2], whereas dynamical features of the non-resonant case were addressed in [3]. Additionally, different longtime behaviours were experimentally observed in [13] after simulating decoherence on one of the modes. Other recent publications such as [7,8] treat the dynamics of quantum correlations in similar systems for a variety of structured environments. Nonetheless, it must be noted that the majority of these works rely on weak systemenvironment coupling assumption.On reference to quantum discord [14], it was introduced to capture the quantumness of correlations. Since the majority of quantum states, including most of the separable ones, have non-zero discord [15], it is said to be more general than entanglement as a measure of nonclassicality. Discord has recentl...

We study stationary entanglement among 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 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-parties interaction with a spatial long-range feature: a main finding is that the presence of a passive oscillator is detrimental for the stationary two-mode entanglement. Furthermore, our results strongly 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.Comment: 15 page, 6 figure

The stationary multipartite entanglement between three interacting harmonic oscillators subjected to deco-herence is analyzed in the largely unexplored non-equilibrium 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 build-up of biseparable steady states, which relates instead just to the relative intensity of thermal fluctuations.