Dynamic dipole-dipole interactions between excitons in quantum dots of different sizes

Abstract

Microphotoluminescence spectra of GaAs/AlGaAs coupled quantum dots (QDs) are given, and proposed to be analyzed by our resonance dynamic dipoledipole interaction (RDDDI) model, based on parity inheritance and exchange of virtual photons among QDs of different sizes. * * * * * Recent developments in nanostructure technology and precision measurements make the resonance dynamic dipole-dipole interaction (RD-DDI) among electric dipoles each confined threedimensionally, i.e. in a quantum dot (QD), important. In this paper, a model of the coherence generating RDDDI between a couple of pyramidally shaped quantum dots of different sizes is developed in terms of virtual photons and parity inheritance [1]. This is important in practice, because so far no real QD pair could be fabricated in an exactly same size. Experimental results suggestive of the RDDDI between excitons in QDs of different sizes are given and proposed to be analyzed by this model . It is naturally expected that this result should be effective for the realization of quantum bits (qubits), quantum controlled not (CN) gates, swap gates, and a solid state quantum computer, as described elsewhere [2].A QD pair is approximated by a couple of two level systems having a total Hamiltonian H with the dipole-dipole interaction H dd .where suffix 0 denotes the non-interacting independent system. The state of the system is expressed either by the wave function (Ψ) or by the ket vectors | 0 i and | 0 j of the ground states (no exciton) at sites i and j respectively, and | 1 i , | 1 j of excited states (an exciton is created in each) as shown in Fig.1.The interaction energy of the RDDDI between a pair of QDs at sites i and j involving real or q |1 i

Multipolar Photonic Interactions between Quantum Dots of Different Sizes

“…As is detailed in reference [2], we attributed the 0.3 meV splittings at peaks 3 and 10 ( "d-d" in the spectrum of Fig.2 ) to the RDDDI between transition dipoles in the pair of QDs having different sizes, hence with different excitation energies. Using dd W ⊥ as the interaction Hamiltonian, the new energy eigen states ψ ± and their eigen energies E ± are obtained, in terms of the original non-coupled states l ψ and r ψ and energies l E and r E .…”

“…The characterization of various quantum dot samples has been done in a comprehensive manner by different measurement techniques as shown elsewherer [2,5]. In the -PL µ , the excitation of the samples was done by an Ar-ion laser beam polarized parallel to the sample base plane.…”

“…We have been interested in expanding the freedom of mankind to harness fast and seemingly weak correlations among quantum dots (QDs) ensemble, manifesting them at macroscopic level on the basis of the recent technological progress in nanometer structure and measurements [1,2]. Especially, the inclusion of the resonance dynamic dipole-dipole interaction (RDDDI, where photons sufficient only for exciting some sites out of numbers of sites are supplied) has been our major concern both in theory and in experiment, as the method to enhance coherence as well as a mean to execute logic operations, giving a prospective model of a solid state integrated circuit for quantum computation [1,2,3].…”

“…Then, numerical plottings of the energy as the functions of the inter-polar distance are given for these interactions, on the basis of the dipole length estimated by our -PL µ (micro-photoluminescence) spectra of GaAs/AlGaAs coupled QDs [2]. Interactions in all the nontrivial combinations of a single charges, dipoles, and quadrupoles are considered, i.e.…”