Monitoring electrically driven cancellation of exciton fine structure in a semiconductor quantum dot by optical orientation

Kowalik, K.; Krebs, O.; Lemaı̂tre, A.; Eblé, B.; Kudelski, A.; Voisin, P.; Seidl, Stefan; Gaj, J. A.

doi:10.1063/1.2805025

Cited by 33 publications

(32 citation statements)

References 22 publications

(17 reference statements)

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“…We find that in addition to the expected reduction in the fine-structure splitting under applied lateral field, as observed in a previous work on randomly nucleated QDs, [14][15][16]20 we observe a strong compensation of the ground-state excitonic Stark shift and a new optically allowed transition that appears under applied bias. We show that these effects do not occur if the field is applied along the growth direction.…”

Section: Introductionsupporting

confidence: 53%

“…For fiber-based quantum cryptography, InAs/InP QDs are particularly attractive since the ground-state transition can be tuned to the telecommunications wavelength of 1.55 m. 6,7 Current proposals for the generation of entangled photon pairs using the biexciton-exciton-vacuum cascade within semiconductor QDs rely on the removal of the fine-structure splitting of the intermediate exciton states. [11][12][13][14][15][16] To date, removal of this anisotropic exchange splitting ͑AES͒ for the exciton has been demonstrated only within randomly located QDs through the application of external magnetic fields, 11 spectral filtering, 12 quantum-dot size and composition engineering, 13 or application of in-plane electric fields, [14][15][16] while the application of a vertical electric field was used to control the charge 17 and field-induced Stark shift of QD states. 18,19 For methods based on the application of an in-plane electric field, however, the oscillator strength of the transitions is significantly reduced at the electric field required to remove the AES.…”

Section: Introductionmentioning

confidence: 99%

“…5,10 With this view in mind, we investigate here the optical emission of excitonic complexes within single deterministically positioned InAs/InP QDs subject to an in-plane electric field, where control over the dot nucleation site allows one to precisely position the electrostatic gates with respect to the dot. Previous work in this area [14][15][16]20,21 used randomly nucleated QDs.…”

Section: Introductionmentioning

confidence: 99%

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Prepositioned single quantum dot in a lateral electric field

et al. 2008

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We examine the effect of a lateral electric field on the optical properties of a single deterministically positioned InAs/InP quantum dot. We show experimentally that the ground-state excitonic Stark shift is significantly reduced in comparison with the single-particle picture and that the lateral electric field introduces a new previously forbidden optical transition. Results of full configuration-interaction calculations show that the Coulomb interactions of electrons and holes are modified by the electric field leading to the compensation of the single-particle Stark shift. The calculations also account for the appearance of the field-activated optical transition as an excitonic recombination event. The comparison of exciton and predicted charged exciton spectra allows us to exclude the presence of charged exciton complexes within the measured emission spectra. The ability to precisely position a single quantum dot and demonstrate control over the electronic properties of such a dot is expected to find application in scalable techniques for quantum information science.

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Section: Introductionsupporting

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Prepositioned single quantum dot in a lateral electric field

et al. 2008

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“…This is attributed to highly elongated quantum dots [23], confirmed by the mean aspect ratio of 0.53 measured by AFM for uncapped SK QDs on InP. For such large FSS, a significant reduction through annealing [24] or the use of external magnetic [25], electric [26,27], or strain fields [28,29] is impractical.…”

Section: Resultsmentioning

confidence: 96%

Universal Growth Scheme for Quantum Dots with Low Fine-Structure Splitting at Various Emission Wavelengths

et al. 2017

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Efficient sources of individual pairs of entangled photons are required for quantum networks to operate using fiber-optic infrastructure. Entangled light can be generated by quantum dots (QDs) with naturally small fine-structure splitting (FSS) between exciton eigenstates. Moreover, QDs can be engineered to emit at standard telecom wavelengths. To achieve sufficient signal intensity for applications, QDs have been incorporated into one-dimensional optical microcavities. However, combining these properties in a single device has so far proved elusive. Here, we introduce a growth strategy to realize QDs with small FSS in the conventional telecom band, and within an optical cavity. Our approach employs ''droplet-epitaxy'' of InAs quantum dots on (001) substrates. We show the scheme improves the symmetry of the dots by 72%. Furthermore, our technique is universal, and produces low FSS QDs by molecular beam epitaxy on GaAs emitting at ∼900 nm, and metal-organic vapor-phase epitaxy on InP emitting at ∼1550 nm, with mean FSS 4× smaller than for Stranski-Krastanow QDs.

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“…Thus, the observation of circular polarization provides a sufficient condition for exciton degeneracy. The measurement principle is analogous to the well-known Hanle measurement, and was used to monitor FSS cancellation by an electric field 37 . To avoid the effect of dynamic nuclear polarization 38 , we set the excitation power at a sufficiently low level, where the average exciton population in the dot was ∼ 0.5.…”

mentioning

confidence: 99%

Vanishing fine-structure splittings in telecommunication-wavelength quantum dots grown on (111)A surfaces by droplet epitaxy

Liu

Nakajima³

et al. 2014

Phys. Rev. B

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The emission cascade of a single quantum dot is a promising source of entangled photons. A prerequisite for this source is the use of a symmetric dot analogous to an atom in a vacuum, but the simultaneous achievement of structural symmetry and emission in a telecom band poses a challenge. Here we report the growth and characterization of highly symmetric InAs/InAlAs quantum dots self-assembled on C3v symmetric InP(111)A. The broad emission spectra cover the O (λ ∼ 1.3 µm), C (λ ∼ 1.55 µmm), and L (λ ∼ 1.6 µm) telecom bands. The distribution of the fine-structure splittings is considerably smaller than those reported in previous works on dots at similar wavelengths. The presence of dots with degenerate exciton lines is further confirmed by the optical orientation technique. Thus, our dot systems are expected to serve as efficient entangled photon emitters for long-distance fiber-based quantum key distribution.Semiconductor quantum dots (QD) are expected to play a central role in quantum information networks. A noteworthy device based on dots is the solid-state single photon source, which ensures absolute security in quantum key distribution (QKD)1 . Since QDs can confine charged carriers in nanometer-sized regions, recombination enables single photons to appear on demand, i.e., synchronously with a master clock shared in networks 2 . QKD over a 50 km commercial fiber has already been demonstrated with QD photon sources, which emitted at a wavelength of 1.5 µm 3 . The transmission distance in that work was limited purely by the absorption loss of silicate fibers. Exceeding this fundamental limit requires the development of quantum link protocols, which exploit the nonlocality inherent in quantum theory. An efficient source of entangled photon pairs is a key element in the realization of such protocols, examples of which include quantum teleportation 4 and entanglement swapping 5 . The generation of entangled photons with semiconductor QDs is directly linked to the singlet configuration of two excitons (X), which form a biexciton (XX). Eventually, two photons associated with the XX-X cascade show polarization correlations independent of the choice of measurement basis, yielding quantum entanglement in the polarization state. However, a common class of QDs exhibits considerable fine-structure splittings (FSS) 6-10 , which exclude entanglement in emitted photons 11 . Numerous attempts have been made to suppress FSS and recover the symmetry of QDs grown on conventional (001) oriented substrates [12][13][14][15][16][17][18][19] . However, from a practical point of view, the reproducible growth of symmetric dots with (at least) near-zero FSS is highly desirable.A noteworthy strategy for achieving such high QD symmetry is the application of C 3v symmetric (111) makes it possible to grow QDs on (111) substrates. Hence, a great reduction in FSS was observed in these QDs 23,24 , which led to the demonstration of entangled photon emission in pyramidal QDs on patterned (111)B substrates 25 , and the filtering-free violation ...

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Monitoring electrically driven cancellation of exciton fine structure in a semiconductor quantum dot by optical orientation

Cited by 33 publications

References 22 publications

Prepositioned single quantum dot in a lateral electric field

Prepositioned single quantum dot in a lateral electric field

Universal Growth Scheme for Quantum Dots with Low Fine-Structure Splitting at Various Emission Wavelengths

Vanishing fine-structure splittings in telecommunication-wavelength quantum dots grown on (111)A surfaces by droplet epitaxy

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