Collective fluorescence and decoherence of a few nearly identical quantum dots

We study the collective interaction of excitons in closely spaced artificial molecules and arrays of nearly identical quantum dots with the electromagnetic modes. We discuss how collective fluorescence builds up in the presence of a small mismatch of the transition energy. We show that a superradiant state of a single exciton in a molecule of two dots with realistic energy mismatch undergoes a two-rate decay. We analyze also the stability of subdecoherent states for non-identical systems.Comment: 7 pages, 5 figure

Partly noiseless encoding of quantum information in quantum dot arrays against phonon-induced pure dephasing

We show that pure dephasing of a quantum dot charge (excitonic) qubit may be reduced for sufficiently slow gating by collectively encoding quantum information in an array of quantum dots. We study the role of the size and structure of the array and of the exciton lifetime for the resulting total error of a single-qubit operation.Comment: Final version; 10 pages, 8 figure

Theory of two-photon processes in quantum dots: coherent evolution and phonon-induced dephasing

The paper discusses two-photon Rabi oscillations between the ground state of a quantum dot and the biexciton state, as well as two-photon oscillations between the two single-exciton states with different circular or linear polarizations. The effect of phonon-induced decoherence on these processes is described and optimal system properties and optical driving conditions for coherent control are identified. It is shown that proper optimalization allows one to control the biexciton system via two-photon transitions with a high fidelity.Comment: 11 pages; moderate change

Electronic and optical properties in non-uniformly shaped QDashes

We theoretically study the optical properties and the electronic structure of highly elongated quantum dots (quantum dashes) and show how carrier trapping due to geometrical fluctuations of the confining potential affects the excitonic spectrum of the system. We focus on the study of the optical properties of a single exciton confined in the structure. The dependence of the absorption and emission intensities on the geometrical properties (depth and position) of the trapping center of a quantum dash is analyzed and the dependence of the degree of linear polarization on these geometrical parameters is studied in detail.Comment: 17 pages, 9 figure

Manifestation of fundamental quantum complementarities in time-domain interference experiments with quantum dots: A theoretical analysis

A theoretical analysis is presented showing that fundamental complementarity between the particle-like properties of an exciton confined in a semiconductor quantum dot and the ability of the same system to show interference may be studied in a time domain interference experiment, similar to those currently performed. The feasibility of such an experiment, including required pulse parameters and the dephasing effect of the environment, is studied.Comment: Final, considerably extended version; 8 pages, 3 figure

Change of decoherence scenario and appearance of localization due to reservoir anharmonicity

Although coupling to a super-Ohmic bosonic reservoir leads only to partial dephasing on short time scales, exponential decay of coherence appears in the Markovian limit (for long times) if anharmonicity of the reservoir is taken into account. This effect not only qualitatively changes the decoherence scenario but also leads to localization processes in which superpositions of spatially separated states dephase with a rate that depends on the distance between the localized states. As an example of the latter process, we study the decay of coherence of an electron state delocalized over two semiconductor quantum dots due to anharmonicity of phonon modes.Comment: 4 pages, 1 figure; moderate changes; auxiliary material added; to appear in Phys. Rev. Let