Quantum Dots for Single- and Entangled-Photon Emitters

Abstract

The efficient generation of polarized single or entangled photons is a crucial requirement for the implementation of quantum key distribution (QKD) systems. Selforganized semiconductor quantum dots (QDs) are capable of emitting one polarized photon or an entangled photon pair at a time using appropriate electrical current injection. We realized a highly efficient single-photon source (SPS) based on well-established semiconductor technology: In a pin structure, a single electron and a single hole are funneled into a single InAs QD using a submicron AlO x current aperture. Efficient radiative recombination leads to emission of single polarized photons with an all-time record purity of the spectrum. Non-classicality of the emitted light without using additional spectral filtering is demonstrated. The out-coupling efficiency and the emission rate are increased by embedding the SPS into a micro-cavity. The design of the micro-cavity is based on detailed modeling to optimize its performance. The resulting resonant single-QD diode is driven at a repetition rate of 1 GHz, exhibiting a second-order correlation function of g ð2Þ ð0Þ ¼ 0. Eventually, QDs grown on (111)-oriented substrates are proposed as a source of entangled photon pairs. Intrinsic symmetry-lowering effects leading to the splitting of the exciton bright states are shown to be absent for this substrate orientation. As a result, the XX ! X ! 0 recombination cascade of a QD can be used for the generation of entangled photons without further tuning of the fine-structure splitting via QD size and/or shape.

Semiconductor nanostructures for flying q-bits and green photonics

“…It is straightforward to move to wurtzite structures, like GaN/AlN QDs, which show the advantage of much larger localization energies of the charge carriers and thus larger thermal stability, suggesting room-temperature operation of the SPEs. Recent experiments showed huge fine structure splitting up to 7 meV for GaN/AlN QDs [32][33][34]. Single photon emission up to RT has been indeed reported for QDs based on the (InGaAl)N material system.…”

“…QD lasers emitting on the ground state exhibit a stability enhancement by 23 dB against feedback due to the strong damping of the (2) (0) = 0) with 1-GHz repetition rate, taking into account the limited time resolution of 0.7 ns of the setup, from Refs. [32][33][34]. relaxation oscillations.…”

Theoretical analyses of the elastic and electronic properties of InAs QDs and QD-in-WELL structures grown on GaAs high index substrates

“…In dissimilarity to the QDs grown on GaAs(001) substrate, the QDs grown on GaAs(11N) are highly advantage to will be applied in quantum cryptography network [1][2][3][4] and in photovoltaic cells [5]. This is due to the significant piezo-electric field (PZ-field), surface polarity and the difference chemical potentials in surfaces [6,7].…”

Сверхминиатюрные излучатели на основе одиночной (111) In(Ga)As квантовой точки и гибридного микрорезонатора

“…Оди-ночная КТ может быть источником " запутанных" пар фотонов в процессе каскадной рекомбинации биэкси-тона и экситона в случае, если экситонные состояния вырождены по энергии или их расщепление E FS не превышает естественной ширины экситонных уровней Ŵ X = /τ X , где τ X -время жизни экситона. В этом случае излучается пара фотонов, запутанных по поляри-зации [4][5][6]. В КТ, синтезированных на подложках (001) GaAs, расщепление экситонных состояний E FS , как правило, превышает естественную ширину экситонных уровней Ŵ X .…”