Multipolar Photonic Interactions between Quantum Dots of Different Sizes
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0959-M05-04
Multipolar Photonic Interactions between Quantum Dots of Different Sizes Hideaki Matsueda Department of Information Science, Kochi University, 2-5-1 Akebono-cho, Kochi, 780-8520, Japan
ABSTRACT Multipolar interactions between quantum dots involving real and virtual photons are compared on the basis of our µ -PL (micro-photoluminescence) spectra of coupled QDs (quantum dots), and suggested as the principle of intra-device, inter-device, and inter-chip interconnections and logical operations, with the device concepts for solid state nanometer networks and a quantum computer. INTRODUCTION 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]. In this paper, first a theoretical outlook of the possible coherent multipolar interactions involving virtual as well as real photons will be given. Interactions in all the nontrivial combinations of a single charges, dipoles, and quadrupoles are considered, i.e. each multipole exerts its potential on other multipoles yielding the maximum interaction energies Wcs , Wcd , Wds , Wdd ,Wdq , Wqs , Wqd , and Wqq where the first suffix refers to Colombic (c), dipolar (d), and quadrupolar (q) potentials respectively, and the second to a single charge (s), dipole (d), and quadrupole (q) respectively. Further, the second order perturbation energy due to the dipoledipole interaction Wdd ⊥ p is also included, since this energy may be significant at very close distance as known as van der Waals force. 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 µ -PL (micro-photoluminescence) spectra of GaAs/AlGaAs coupled QDs [2]. Using the time-energy uncertainty, each interaction energy will give the lifetime of the photon mediating the interaction, or the coherence time for the interaction. Then the coherence length or the range of the interaction is estimated, yielding the limiting distance for the possible interconnection by each multipolar interaction. Some interactions that may be useful for intra-device (short range), inter-device (intra-chip, medium range) and inter-chip (long range) interconnections and logic operations are selectively discussed. Moreover, prospective device concepts to implement these interconnections and the logical operations are given.
THEORETICAL CONSIDERATION Derivation of the Multipoles Coulomb law shows,
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