78 research outputs found
Superradiance and enhanced luminescence from ensembles of a few self-assembled quantum dots
We study the evolution of photoluminescence (PL) from homogeneous and
inhomogeneous ensembles of a few coupled QDs. We discuss the relation between
signals from a given QD ensemble under strong and weak excitation (full
inversion and linear response regimes): A system homogeneous enough to manifest
superradiant emission when strongly inverted shows a non-exponential decay of
the PL signal under spatially coherent weak excitation. In an inhomogeneous
ensemble the PL decay is always nearly exponential with a qualitatively
different form of the time dependence in the two excitation regimes and with a
higher rate under weak excitation.Comment: 5 pages, 3 figures; moderate changes and extension
Quantum-state transfer in spin chains via isolated resonance of terminal spins
We propose a quantum-state transfer protocol in a spin chain that requires
only the control of the spins at the ends of the quantum wire. The protocol is
to a large extent insensitive to inhomogeneity caused by local magnetic fields
and perturbation of exchange couplings. Moreover, apart from the free evolution
regime, it allows one to induce an adiabatic spin transfer, which provides the
possibility of performing the transfer on demand. We also show that the amount
of information leaking into the central part of the chain is small throughout
the whole transfer process (which protects the information sent from being
eavesdropped) and can be controlled by the magnitude of the external magnetic
field.Comment: 7 pages, 5 figures. Published versio
Second-order polaron resonances in self assembled quantum dots
We theoretically study the optical properties of an InAs/GaAs quantum dot
(QD) near the area of the second-order resonance between an electron confined
in the QD and two longitudinal optical phonons. We present the absorption
spectra of an inhomogeneously broadened QD ensemble and show that the minimal
model needed for an accurate description of such a system needs to account for
3-phonon states. We study also the influence of the QD height to width ratio on
the optical properties of the polaron system. The dependence of the width of
the resonance and the position of the second-order resonant feature on the
height to width ratio is presented.Comment: 4 pages, 3 figure
Electron states, phonon-assisted relaxation and tunneling in self-assembled quantum dot molecules in an electric field
We present a theoretical analysis of the phonon-assisted relaxation in a
system composed of two self-assembled vertically stacked quantum dots. We
construct realistic model, which takes into account the geometry and strain
distribution in the system. We calculate phonon-assisted relaxation rates
between the two lowest states (in one- and two-electron cases). The relaxation
rates and energy levels are studied as a function of external (axial) electric
field and geometry of the structure (dot sizes). We show that the relaxation
times can be as low as 1~ps but efficent relaxation occurs only for very finely
tuned dots.Comment: 3 page
Tunneling transfer protocol in a quantum dot chain immune to inhomogeneity
We propose a quantum dot (QD) implementation of a quantum state transfer
channel. The proposed channel consists of N vertically stacked QDs with the
nearest neighbor tunnel coupling, placed in an axial electric field. We show
that the system supports high-fidelity transfer of the state of a terminal dot
both by free evolution and by adiabatic transfer. The protocol is to a large
extent insensitive to inhomogeneity of the energy parameters of the dots and
requires only a global electric field.Comment: 3 pages, 6 figure
Collective spontaneous emission from pairs of quantum dots: long-range vs. short-range couplings
We study the spontaneous emission from a coherently delocalized exciton state
in a double quantum dot as a function of the distance between the dots,
focusing on the similarities and differences between the cases of radiative
(long-range, dipole) and tunnel coupling between the excitons in the dots. We
show that there may be no qualitative difference between the collective
emission induced by these two coupling types in spite of their essentially
different physical properties.Comment: 3 pages, 2 figures. Conference "Jaszowiec 2011
- …