All-optical depletion of dark excitons from a semiconductor quantum dot

Schmidgall, E. R.; Schwartz, I.; Cogan, Dan; Gantz, Liron; Heindel, Tobias; Reitzenstein, Stephan; Gershoni, D.

doi:10.1063/1.4921000

Cited by 23 publications

(29 citation statements)

References 34 publications

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“…As can be seen in Figs .4b and d our fitting procedure agrees with all the measured data points within one standard deviation of the experimental uncertainty. We now proceed by first depleting the QD from charges and from the remaining DE using a 7-ns-long optical pulse as described elsewhere [44]. We then write the DE spin state using a 12-ps optical π−pulse to an excited DE state [32].…”

Section: Methodsmentioning

confidence: 99%

“…Color-matched ovals represent one standard deviation of the experimental uncertainty of the measured-states, while color-matched arrows represent the six initialized-states. The length of the arrows represents the degree of polarization of the initializations, independently measured to be 0.82, due to the finite efficiency of the optical depletion [44].…”

Section: Methodsmentioning

confidence: 99%

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Complete state tomography of a quantum dot spin qubit

Cogan

Peniakov

et al. 2020

Phys. Rev. B

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Semiconductor quantum dots are probably the preferred choice for interfacing anchored, matter spin qubits and flying photonic qubits. While full tomography of a flying qubit or light polarization is in general straightforward, matter spin tomography is a challenging and resource-consuming task.Here we present a novel all-optical method for conducting full tomography of quantum-dot-confined spins. Our method is applicable for electronic spin configurations such as the conduction-band electron, the valence-band hole, and for electron-hole pairs such as the bright and the dark exciton. We excite the spin qubit using short resonantly tuned, polarized optical pulse, which coherently converts the qubit to an excited qubit that decays by emitting a polarized single-photon. We perform the tomography by using two different orthogonal, linearly polarized excitations, followed by time-resolved measurements of the degree of circular polarization of the emitted light from the decaying excited qubit. We demonstrate our method on the dark exciton spin state with fidelity of 0.94, mainly limited by the accuracy of our polarization analyzers. arXiv:1910.05024v1 [quant-ph]

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Complete state tomography of a quantum dot spin qubit

Cogan

Peniakov

et al. 2020

Phys. Rev. B

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“…Due to the lack of optical activity dark excitons possess significantly longer lifetimes than bright excitons 11 , which offers potential for applications in quantum memory, but also makes their preparation more challenging. Due to these prospects several mechanisms for the controlled preparation of the dark exciton have been recently studied either by relaxations from higher excited states [12][13][14][15] or valence band mixing 16 . We recently proposed a scheme to direct optical address the dark exciton by using a combination of a single chirped laser pulse and a tilted magnetic field and we also showed that at sufficiently low temperatures the process is essentially unaffected by phonons 17 .…”

Section: Introductionmentioning

confidence: 99%

Phonon-assisted dark exciton preparation in a quantum dot

2017

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In semiconductor quantum dots the coupling to the environment, i.e. to phonons, plays a crucial role for optical state preparation. We analyze the phonon impact on two methods for a direct optical preparation of the dark exciton, which is enabled by a tilted magnetic field: the excitation with a chirped laser pulse and the excitation with a detuned pulse. Our study reveals that for both methods phonons either do not impede the proposed mechanism or are even useful by widening the parameter range where a dark state preparation is possible due to phonon-assisted dark exciton preparation. In view of the positive impact of phonons on the optical preparation the use of dark excitons in quantum dots becomes even more attractive.

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“…Specifically, there is increasing consensus about the role of dark excitons 54,55 in connection with still elusive excitonic BEC. It has been repeatedly advised that standard optical tools, which indirectly 22,56,57 study such condensations by looking only at photons coming out once excitonic quasi particles decay, might actually overlook the BEC all together.…”

Section: Discussionmentioning

confidence: 99%

Negative activation energy and dielectric signatures of excitons and excitonic Mott transitions in quantum confined laser structures

Bhunia

Bansal

Henini

et al. 2016

Journal of Applied Physics

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Mostly, optical spectroscopies are used to investigate the physics of excitons, whereas their electrical evidences are hardly explored. Here, we examined a forward bias activated differential capacitance response of GaInP/AlGaInP based multi-quantum well laser diodes to trace the presence of excitons using electrical measurements. Occurrence of "negative activation energy" after light emission is understood as thermodynamical signature of steady state excitonic population under intermediate range of carrier injections. Similar corroborative results are also observed in an InGaAs/GaAs quantum dot laser structure grown by molecular beam epitaxy. With increasing biases, the measured differential capacitance response slowly vanishes. This represents gradual Mott transition of an excitonic phase into an electron-hole plasma in a GaInP/AlGaInP laser diode. This is further substantiated by more and more exponentially looking shapes of high energy tails in electroluminescence spectra with increasing forward bias, which originates from a growing non-degenerate population of free electrons and holes. Such an experimental correlation between electrical and optical properties of excitons can be used to advance the next generation excitonic devices. Published by AIP Publishing. [http://dx

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All-optical depletion of dark excitons from a semiconductor quantum dot

Cited by 23 publications

References 34 publications

Complete state tomography of a quantum dot spin qubit

Complete state tomography of a quantum dot spin qubit

Phonon-assisted dark exciton preparation in a quantum dot

Negative activation energy and dielectric signatures of excitons and excitonic Mott transitions in quantum confined laser structures

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