A Langevin Canonical Approach to the Study of Quantum Stochastic Resonance in Chiral Molecules

A Langevin canonical framework for a chiral two-level system coupled to a bath of harmonic oscillators is used within a coupling scheme different from the well-known spin-boson model to study the quantum stochastic resonance for chiral molecules. This process refers to the amplification of the response to an external periodic signal at a certain value of the noise strength, being a cooperative effect of friction, noise, and periodic driving occurring in a bistable system. Furthermore, from this stochastic dynamics within the Markovian regime and Ohmic friction, the competing process between tunneling and the parity violating energy difference present in this type of chiral systems plays a fundamental role. This mechanism is finally proposed to observe the so-far elusive parity-violating energy difference in chiral molecules.Helen Clara Peñate-Rodríguez and Germán Rojas-Lorenzo acknowledge a scientific project from InSTEC. Pedro Bargueño acknowledge the support from the Faculty of Science and Vicerrectoría de Investigaciones of Universidad de Los Andes, Bogotá, Colombia. Salvador Miret-Artés acknowledges a grant with Ref. FIS2014-52172-C2-1-P from the Ministerio de Economía y Competitividad (Spain). We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)

Geometric phase and parity-violating energy difference locking of chiral molecules

Geometric phases within a canonical formulation of chiral molecules are analyzed paying special attention to the fundamental role played by the parity violating energy difference. We study the Hamiltonian dynamics in terms of canonically conjugate variables, showing how parity-violating energy difference could be locked (PVED-locking) by means of a circularly polarized electric field. Signatures of this locking are predicted to occur both in the geometric phase and in the interference between chiral states. © 2011 Elsevier B.V. All rights reserved.This work has been funded by the MICINN (Spain) through Grant Nos. CTQ2008-02578, FIS2007-62006, FIS2010-18132, and the Juan de la Cierva program (P.B.).Peer Reviewe

Dissipative geometric phase and decoherence in parity-violating chiral molecules

Within a generalized Langevin framework for open quantum systems, the cyclic evolution of a two-level system is analyzed in terms of the geometric phase extended to dissipative systems for Ohmic friction. This proposal is applied to the dynamics of chiral molecules where the tunneling and parity violating effects are competing. The effect of different system-bath coupling functions in the dissipated energy is shown to be crucial to understand the behavior of the geometric phase as well as the decoherence displayed by the corresponding interference patterns. © 2012 American Institute of Physics.This work has been funded by the MICINN (Spain) through Grant Nos. CTQ2008-02578, FIS2010-18132, and by the Comunidad Autónoma de Madrid, Grant No. S-2009/MAT/1467. P.B. acknowledges a Juan de la Cierva fellowship from the MICINN and A.D.-U. acknowledges a JAE fellowship from CSIC. H.C.P.-R. and G.R.-L. acknowledge a scientific project from INSTEC.Peer Reviewe

Dissipative Bohmian mechanics within the Caldirola-Kanai framework: A trajectory analysis of wave-packet dynamics in viscid media

20 pags.; 5 figs.Classical viscid media are quite common in our everyday life. However, we are not used to find such media in quantum mechanics, and much less to analyze their effects on the dynamics of quantum systems. In this regard, the Caldirola-Kanai time-dependent Hamiltonian constitutes an appealing model, accounting for friction without including environmental fluctuations (as it happens, for example, with quantum Brownian motion). Here, a Bohmian analysis of the associated friction dynamics is provided in order to understand how a hypothetical, purely quantum viscid medium would act on a wave packet from a (quantum) hydrodynamic viewpoint. To this purpose, a series of paradigmatic contexts have been chosen, such as the free particle, the motion under the action of a linear potential, the harmonic oscillator, or the superposition of two coherent wave packets. Apart from their analyticity, these examples illustrate interesting emerging behaviors, such as localization by >quantum freezing> or a particular type of quantum-classical correspondence. The reliability of the results analytically determined has been checked by means of numerical simulations, which has served to investigate other problems lacking of such analyticity (e.g.,the coherent superpositions). © 2014 Elsevier Inc.This work has been supported by the Ministerio de Economía y Competitividad (Spain) under Project FIS2011-29596-C02-01; AS is also grateful for a “Ramón y Cajal” Research Grant.Peer Reviewe

Friction-induced enhancement in the optical activity of interacting chiral molecules

The stability of chiral molecules described by a non-linear two-state system which accounts for mean-field interactions between different isomers, including any external chiral influence (in particular, the parity violating energy difference) is investigated. By introducing the population and phase difference of the chiral states as a pair of canonical variables, driving an analogy to a bosonic Josephson junction, our study to include dissipative effects in condensed phase described by a Caldeira-Leggett like Hamiltonian is extended using the Langevin formalism. Dissipative effects produce an enhancement in the population difference, not leading to racemization. © 2011 Elsevier B.V. All rights reserved.Peer Reviewe