12 research outputs found
Non-Markovian perturbation theories for phonon effects in strong-coupling cavity quantum electrodynamics
Phonon interactions are inevitable in cavity quantum electrodynamical systems
based on solid-state emitters or fluorescent molecules, where vibrations of the
lattice or chemical bonds couple to the electronic degrees of freedom. Due to
the non-Markovian response of the vibrational environment, it remains a
significant theoretical challenge to describe such effects in a computationally
efficient manner. This is particularly pronounced when the emitter-cavity
coupling is comparable to or larger than the typical phonon energy range, and
polariton formation coincides with vibrational dressing of the optical
transitions. In this Article, we consider four non-Markovian perturbative
master equation approaches to describe such dynamics over a broad range of
light-matter coupling strengths and compare them to numerically exact reference
calculations using a tensor network. The master equations are derived using
different basis transformations and a perturbative expansion in the new basis
is subsequently introduced and analyzed. We find that two approaches are
particularly successful and robust. The first of these is suggested and
developed in this Article and is based on a vibrational dressing of the
exciton-cavity polaritons. This enables the description of distinct
phonon-polariton sidebands that appear when the polariton splitting exceeds the
typical phonon frequency scale in the environment. The second approach is based
on a variationally optimized polaronic vibrational dressing of the electronic
state. Both of these approaches demonstrate good qualitative and quantitative
agreement with reference calculations of the emission spectrum and are
numerically robust, even at elevated temperatures, where the thermal phonon
population is significant.Comment: 17 pages, 10 figure
A stochastic approach to the quantum noise of a single-emitter nanolaser
It is shown that the intensity quantum noise of a single-emitter nanolaser
can be accurately computed by adopting a stochastic interpretation of the
standard rate equation model under the only assumption that the emitter
excitation and photon number are stochastic variables with integer values. This
extends the validity of rate equations beyond the mean-field limit and avoids
using the standard Langevin approach, which is shown to fail for few emitters.
The model is validated by comparison to full quantum simulations of the
relative intensity noise and second-order intensity correlation function,
g(2)({\tau} ). Surprisingly, even when the full quantum model displays vacuum
Rabi oscillations, which are not accounted for by rate equations, the intensity
quantum noise is correctly predicted by the stochastic approach. Adopting a
simple discretization of the emitter and photon populations, thus, goes a long
way in describing quantum noise in lasers. Besides providing a versatile and
easy-to-use tool for modeling a new generation of nanolasers with many possible
applications, these results provide insight into the fundamental nature of
quantum noise in lasers.Comment: Revised and resubmitted for revie
Modal properties of dielectric bowtie cavities with deep sub-wavelength confinement
We present a design for an optical dielectric bowtie cavity which features
deep sub-wavelength confinement of light. The cavity is derived via
simplification of a complex geometry identified through inverse design by
topology optimization, and it successfully retains the extreme properties of
the original structure, including an effective mode volume of at its center. Based on
this design, we present a modal analysis to show that the Purcell factor can be
well described by a single quasinormal mode in a wide bandwidth of interest.
Owing to the small mode volume, moreover, the cavity exhibits a remarkable
sensitivity to local shape deformations, which we show to be well described by
perturbation theory. The intuitive simplification approach to inverse design
geometries coupled with the quasinormal mode analysis demonstrated in this work
provides a powerful modeling framework for the emerging field of dielectric
cavities with deep sub-wavelength confinement.Comment: 24 pages, 13 figures, research articl
Unidirectional Quantum Transport in Optically Driven -type Quantum Dot Chains
We predict a mechanism for achieving complete population inversion in a
continuously driven InAs/GaAs semiconductor quantum dot featuring -type
transitions. This highly nonequilibrium steady state is enabled by the
interplay between -type interband transitions and a non-Markovian
decoherence mechanism, introduced by acoustic phonons. The population trapping
mechanism is generalized to a chain of coupled emitters. Exploiting the
population inversion, we predict unidirectional excitation transport from one
end of the chain to the other without external bias, independent of the unitary
interdot coupling mechanism