Atomistic theory of dark excitons in self-assembled quantum dots of reduced symmetry

Zieliński, Michał; Don, Yaroslav; Gershoni, D.

doi:10.1103/physrevb.91.085403

Cited by 52 publications

(81 citation statements)

References 53 publications

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“…Quantum dots 1 (QDs) main spectral properties are governed by size, shape and average chemical composition. 2,3 However the detailed, fine structure of their optical spectra, 4 that plays an essential role for applications in quantum optics [5][6][7] and information [8][9][10] , is determined by atomic scale details related to microscopic symmetry of underlying lattice, [11][12][13][14] presence of facets, 15 and alloying randomness. [16][17][18][19] Regarding potential applications, the bright exciton (BE) recombination in QDs is considered as a tool for generation of entangled photons through biexciton-exciton cascade, 20,21 whereas the dark exciton (DE) gained attention as a candidate for longlived, though optically addressable quantum bit.…”

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confidence: 99%

Spectra of dark and bright excitons in alloyed nanowire quantum dots

Zieliński

2019

Phys. Rev. B

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Excitons in alloyed nanowire quantum dots have unique spectra as shown here using atomistic calculations. The bright exciton splitting is triggered solely by alloying and despite cylindrical quantum dot shape reaches over 15 µeV, contrary to previous theoretical predictions, however, in line with experimental data. This splitting can however be tuned by electric field to go below 1 µeV threshold. The dark exciton optical activity is also strongly affected by alloying reaching notable 1/3500 fraction of the bright exciton and having large out-of-plane polarized component.

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confidence: 99%

Spectra of dark and bright excitons in alloyed nanowire quantum dots

Zieliński

2019

Phys. Rev. B

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“…The coupling strengths V C of the Coulomb resonances in the numerical calculation are reduced compared to the maximal coupling strengths of 2V C(p1) = 0.6 meV that we experimentally observe in Fig.5. This suggests that another symmetry breaking effect [39] and spin-orbit coupling [26] further influence the coupling strength V C of the Coulomb resonances.…”

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Coulomb Mediated Hybridization of Excitons in Coupled Quantum Dots

et al. 2016

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We report the Coulomb mediated hybridization of excitonic states in an optically active, artificial quantum dot molecule. By probing the optical response of the artificial molecule as a function of the static electric field applied along the molecular axis, we observe unexpected avoided level crossings that do not arise from the dominant single particle tunnel coupling. We identify a new few-particle coupling mechanism stemming from Coulomb interactions between different neutral exciton states. Such Coulomb resonances hybridize the exciton wave function over four different electron and hole single-particle orbitals. Comparisons of experimental observations with microscopic 8-band k · p calculations taking into account a realistic quantum dot geometry show good agreement and reveal that the Coulomb resonances arise from broken symmetry in the artificial molecule.Understanding and controlling the fundamental interactions that couple discrete quantum states lies at the very heart of applied quantum science. For example, couplings between distinct physical subsystems mediated by the Coulomb interaction can be used to entangle qubits electrostatically [1], to build single-photon transistors on the basis of Förster resonances [2] or to control resonant energy transfer [3]. Strong tunnel couplings between proximal quantum dots have been shown to facilitate electrical and optical spin-qubit operations [4,5] while long range magnetic dipolar interactions have been exploited for prototype quantum registers [6]. Thus the nature of quantum couplings has been under extensive investigation for many prototypical quantum systems. Examples include naturally occurring atoms [3,7,8] and defect centers [9,10] as well as artificial atoms and molecules [11][12][13]. Due to advanced nanostructure fabrication techniques [14,15] and efficient coupling to light [16,17], artificial molecules consisting of pairs of semiconductor quantum dots (QDs) have emerged as ideal prototypical solid-state systems to investigate and electrically control interactions between proximal quantum systems [11,12].By embedding a QD-molecule into the intrinsic region of a diode structure, exciton states in the different QDs can be tuned into and out of resonance by controlling the electric field along the growth direction [11,12]. The fundamental signatures of quantum couplings are avoided level crossings in the electronic energy level structure of a QD-molecule as single particle states are tuned in and out of resonance [18]. The importance of Coulomb interactions has been pointed out for the form and position of resonances in QD-molecule systems [19][20][21]. However, single particle tunneling that either hybridizes single electrons or holes remains the dominant coupling mechanism in these cases [11][12][13][22][23][24][25]. Most recently another resonant coupling mechanism with an inherently two particle nature has been predicted theoretically that entirely relies on the Coulomb mediated interaction between two different exciton states [26]. In strong contra...

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“…This means that even if the external field in the LR scheme is weak enough to preserve a pure Faraday geometry, dipole-forbidden transitions may still occur with some small, but finite probability, both for the original and the hole-spin variant of the LR protocol. Similarly, in the DE system z-polarised 'forbidden' transitions are also present due to hole sub-band mixing, although these transitions in this system are significantly weaker 68,69 . In addition to hh-lh mixing, the DE scheme also suffers from dark-bright exciton (DE-BE) state mixing due to the breaking of the C 2v symmetry, although this effect is much weaker than the hh-lh mixing.…”

Section: Effects Of Hole State Mixingmentioning

confidence: 82%

Frequency-encoded linear cluster states with coherent Raman photons

et al. 2018

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Entangled multi-qubit states are an essential resource for quantum information and computation. Solid-state emitters can mediate interactions between subsequently emitted photons via their spin, thus offering a route towards generating entangled multi-photon states. However, existing schemes typically rely on the excitation-relaxation of the emitter, resulting in single photons limited by the emitter's radiative lifetime, suffering from considerable practical limitations, for self-assembled quantum dots most notably the limited spin coherence time due to Overhauser magnetic field fluctuations. We here propose an alternative approach based on a spin-Λ system that overcomes the limitations of previous proposals. Studying the example of spin-flip Raman scattering of self-assembled quantum dots in Voigt geometry, we argue that weakly driven hole spins constitute a promising platform for the practical generation of frequency-entangled photonic cluster states.

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Atomistic theory of dark excitons in self-assembled quantum dots of reduced symmetry

Cited by 52 publications

References 53 publications

Spectra of dark and bright excitons in alloyed nanowire quantum dots

Spectra of dark and bright excitons in alloyed nanowire quantum dots

Coulomb Mediated Hybridization of Excitons in Coupled Quantum Dots

Frequency-encoded linear cluster states with coherent Raman photons

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