arXiv subjects

Herbert Vinck-Posada

Publications and source records attributed to Herbert Vinck-Posada.

35 records · Page 2Linked to original sources

arXiv2019

Phonon-assisted tunnelling in a double quantum dot molecule immersed in a cavity

The effects caused by phonon-assisted tunnelling (PhAT) in a double quantum dot (QD) molecule immersed in a cavity were studied under the quantum Markovian master equation formalism in order to account for dissipation phenomena. We explain how for higher PhAT rates, a stronger interaction between a QD and the cavity at off-resonance takes place through the resonant interaction of another QD and the cavity, where the QDs interact through tunnelling. A closer look at the system's allowed optical transitions as a function of PhAT rates showed coalescence of the transition energies, leading to a loss of spectroscopic resolution in the photoluminescence (PL) spectrum. This coalescence occurs at several exceptional points, suggesting a quantum dynamical phase transition.

cond-mat.mes-hall↗

arXiv2018

A comparative study on different non-Hermitian approaches for modeling open quantum systems

In this paper, we test and compare the performance of two different theoretical methods that use anti-Hermitian terms for modeling open quantum systems. It is, the non-Hermitian quantum mechanics method (NHQM) and the recent methodology known as corrected non-Hermitian effective Hamiltonian (corrected NHEH) approach. In particular, we provide a comprehensive analysis of the performance of these two theoretical approaches by describing the dynamics of the pumped-dissipative Jaynes--Cummings model. Our results demonstrate that whereas the NHQM method fails for describing correctly the time evolution of the density matrix elements as well as the quantum fidelity measure. The corrected NHEH approach shows an excellent agreement with simulations based on the Lindblad master equation formalism.

quant-ph↗

arXiv2018

The strange attraction phenomenon in cQED: the intermediate quantum coupling regime

We theoretically investigate the strange phenomenon of attraction between the cavity mode and the exciton mode that has been experimentally observed in a photonic crystal cavity. Our results within the Lindblad master equation approach successfully explain why the apparent cavity-to-exciton spectral shifting occurs, and how this phenomenon is a manifestation of a dynamical phase transition in the system. Moreover, our findings are in good qualitative agreement with pioneer experimental results as well as support the hypothesis that an intermediate coupling regime exists in the cavity quantum electrodynamics. In fact, this new quantum regime exhibits phenomenology from both weak and strong coupling regimes simultaneously.

quant-ph↗

arXiv2017

Explanation of the intriguing quantum phenomenon of the off-resonant cavity mode emission

We theoretically investigate the unexpected occurrence of an extra emission peak that has been experimentally observed in off-resonant studies of cavity QED systems. Our results within the Markovian master equation approach successfully explain why the central peak arises, and how it reveals that the system is suffering a dynamical phase transition induced by the phonon-mediated coupling. Our findings are in perfect agreement with previous reported experimental results and for the first time the fundamental physics behind this quantum phenomenon is understood.

quant-ph↗

arXiv2015

Estudio Teórico del espectro de emisión para un sistema microcavidad-punto cuántico en una aproximación de campo medio (Theoretical study of emission spectrum for a quantum dot-microcavity system in a mean field approximation)

En este trabajo, se obtiene una expresión numérica para calcular el espectro de emisión de un sistema microcavidad-punto cuántico usando una teoría de campo medio en el formalismo de la matriz densidad. El sistema modelado es un micropilar semiconductor que contiene un único punto cuántico en el interior de la microcavidad, este sistema presenta pérdida de fotones a través de los espejos de la cavidad y bombeo de excitones al punto cuántico. Obtenemos una ecuación maestra de campo medio no lineal que nos permite calcular el espectro de emisión. In this work, we deduce a numerical expression to calculate the emission spectrum for a quantum dot-microcavity system, using a mean field theory in the density matrix formalism. The open system modeled, is a typical semiconductor micropillar that contains a single quantum dot inside a microcavity, this system presents leakage of photons through cavity mirrors and pumping of excitons to the quantum dot. We obtain a mean field nonlinear master equation that allow us calculate the emission spectrum.

cond-mat.mes-hall↗

arXiv2015

Green's functions technique for calculating the emission spectrum in a quantum dot-cavity system

We introduce the Green's functions technique as an alternative theory to the quantum regression theorem formalism for calculating the two-time correlation functions in open quantum systems. In particular, we investigate the potential of this theoretical approach by its application to compute the emission spectrum of a dissipative system composed by a single quantum dot inside of a semiconductor cavity. We also describe a simple algorithm based on the Green's functions technique for calculating the emission spectrum of the quantum dot as well as of the cavity which can easily be implemented in any numerical linear algebra package. We find that the Green's functions technique demonstrates a better accuracy and efficiency in the calculation of the emission spectrum and it allows to overcome the inherent theoretical difficulties associated to the direct application of the quantum regression theorem approach.

quant-ph↗

arXiv2013

Preparation of a three-photon state in a nonlinear cavity - quantum dot system

We study theoretically the properties of a three-photon state prepared inside a semiconductor cavity, due to the interaction between a quantum dot and an electromagnetic field, and two consecutive spontaneous parametric downconversion (SPDC) processes. Thus, we consider a scheme involving three modes of the electromagnetic field, whose frequencies are given by the SPDC processes: $ω_0 \rightarrow ω_1 + ω_2$, and $ω_2 \rightarrow ω_1 + ω_1$. Furthermore, we study the low excitation regime, in which a three-photon state is accessible within the system's dynamics.

quant-ph↗

arXiv2012

The Role of a Polariton Bath in the Emission Spectrum of an Open Nanocavity-Quantum Dot System

We investigate the effect of a polariton bath on the photoluminescence (PL) spectrum of the elementary excitations for a confined nanocavity-quantum dot (nC-QD) system. We modeled the nC-QD system as a two-level exciton in strong coupling with a single photonic cavity mode interacting with its environment. The non-hamiltonian processes induced by the environment are taken into account via a Born-Markov master equation which includes: gain and loss of excitons and photons into/out of the cavity, a dephasing mechanism produced by phonon scattering in the semiconductor lattice and gain and loss of polaritons due to the already mentioned polariton bath. In order to validate our phenomenological model, we fit an experimental spectrum to extract the values of all parameters appearing in the master equation. Our results show that polariton pumping and loss rates are comparable to the other parameters and therefore we have a first evidence that the polariton bath we proposed has a significant role in the dynamics of a nC-QD system.

cond-mat.mes-hall↗

arXiv2011

Strong coupling of two interacting excitons confined in a nanocavity-quantum-dot system

We present a study of the strong coupling between radiation and matter, considering a system of two quantum dots, which are in mutual interaction and interacting with a single mode of light confined in a semiconductor nanocavity. We take into account dissipative mechanisms such as the escape of the cavity photons, decay of the quantum dot excitons by spontaneous emission, and independent exciton pumping. It is shown that the mutual interaction between the dots can be measured off-resonance, only if the strong coupling condition is reached. Using the quantum regression theorem, a reasonable definition of the dynamical coupling regimes is introduced in terms of the complex Rabi frequency. Finally, the emission spectrum for relevant conditions is presented and compared with the above definition, demonstrating that the interaction between the excitons does not affect the Strong Coupling.

cond-mat.str-el↗

arXiv2010

Density operator of a system pumped with polaritons: A Jaynes-Cummings like approach

We investigate the effects of considering two different incoherent pumpings over a microcavity-quantum dot system modelled using the Jaynes-Cummings Hamiltonian. When the system is incoherently pumped with polaritons it is able to sustain a large number of photons inside the cavity with Poisson-like statistics in the stationary limit, and also leads to a separable exciton-photon state. We also investigate the effects of both types of pumpings (Excitonic and Polaritonic) in the emission spectrum of the cavity. We show that the polaritonic pumping as considered here is unable to modify the dynamical regimes of the system as the excitonics pumping does. Finally, we obtain a closed form expression for the negativity of the density matrices that the quantum master equation considered here generates.

cond-mat.mes-hall↗

arXiv2010

Non-Classical Behaviour of Scalar Wave Fields in Any State of Spatial Coherence and Point Sources in the Phase-Space Representation

In the framework of the spatial coherence wavelets, different features of the first-order spatial coherence (Young's interference) are analysed by calculating the corresponding marginal power spectrum, a close related quantity to the classical Wigner Distribution Function (WDF) of the optical field. The consideration of radiant and virtual point sources evidences some effects, conventionally attributed to non-classical correlations of light, although such type of correlations are not explicitly included in the model. Specifically, a light state is produced that has similar morphology to the WDF of the well-known quantum Schrödinger cat state.

cond-mat.mes-hall↗

arXiv2009

Ultracold atoms in optical lattices induced by photonic crystals

We propose a way of generating optical lattices embedded in photonic crystals. By setting up extended modes in photonic crystals, ultracold atoms can be mounted in different types of field intensity distributions. This novel way of constructing optical lattices can be used to produce more elaborate periodic potentials by manufacturing appropriate geometries of photonic crystals. We exemplify this with a square lattice and comment on the possibility of using geometries with defects.

cond-mat.quant-gas↗

arXiv2009

Characterization of dynamical regimes and entanglement sudden death in a microcavity quantum - dot system

The relation between the dynamical regimes (weak and strong coupling) and entanglement for a dissipative quantum - dot microcavity system is studied. In the framework of a phenomenological temperature model an analysis in both, temporal (population dynamics) and frequency domain (photoluminescence) is carried out in order to identify the associated dynamical behavior. The Wigner function and concurrence are employed to quantify the entanglement in each regime. We find that sudden death of entanglement is a typical characteristic of the strong coupling regime.

cond-mat.mes-hall↗

arXiv2009

Polariton Lasing in a Multilevel Quantum Dot Strongly Coupled To a Single Photon Mode

We present an approximate analytic expression for the photoluminescence spectral function of a model polariton system, which describes a quantum dot, with a finite number of fermionic levels, strongly interacting with the lowest photon mode of a pillar microcavity. Energy eigenvalues and wavefunctions of the electron-hole-photon system are obtained by numerically diagonalizing the Hamiltonian. Pumping and photon losses through the cavity mirrors are described with a master equation, which is solved in order to determine the stationary density matrix. The photon first-order correlation function, from which the spectral function is found, is computed with the help of the Quantum Regression Theorem. The spectral function qualitatively describes the polariton lasing regime in the model, corresponding to pumping rates two orders of magnitude lower than those needed for ordinary (photon) lasing. The second-order coherence functions for the photon and the electron-hole subsystems are computed as functions of the pumping rate.

cond-mat.mes-hall↗

arXiv2007

Micropillar resonator in a magnetic field: Zero and Finite temperature cases

In this work, we present a theoretical study of a quantum dot-microcavity system which includes a constant magnetic field in the growth direction of the micropillar. First, we study the zero temperature case by means of a selfconsistent procedure with a trial function composed by a coherent photon field and a BCS function for the electron-hole pairs. The dependence of the ground-state energy on the magnetic field and the number of polaritons is found. We show that the magnetic field can be used as a control parameter of the photon number, and we make explicit the scaling of the total energy with the number of polaritons. Next, we study this problem at finite temperatures and obtain the scaling of the critical temperature with the number of polaritons.

cond-mat.mes-hall↗

arXiv2006

Photon emission as a source of coherent behaviour of polaritons

We show that the combined effect of photon emission and Coulomb interactions may drive an exciton-polariton system towards a dynamical coherent state, even without phonon thermalization or any other relaxation mechanism. Exact diagonalization results for a finite system (a multilevel quantum dot interacting with the lowest energy photon mode of a microcavity) are presented in support to this statement.

cond-mat.mes-hall↗

arXiv2004

Mean-field dynamics of a quantum dot - microcavity system

Mean-field evolution equations for the exciton and photon populations and polarizations (Bloch-Lamb equations) are written and numerically solved in order to describe the dynamics of electronic states in a quantum dot coupled to the photon field of a microcavity. The equations account for phase space filling effects and Coulomb interactions among carriers, and include also (in a phenomenological way) incoherent pumping of the quantum dot, photon losses through the microcavity mirrors, and electron-hole population decay due to spontaneous emission of the dot. When the dot may support more than one electron-hole pair, asymptotic oscillatory states, with periods between 0.5 and 1.5 ps, are found almost for any values of the system parameters.

cond-mat.mes-hall↗