&lt;title&gt;Entangled exciton states in quantum dot molecules&lt;/title&gt;

Bayer, М.; Ortner, G.; Larionov, A. V.; Kress, A.; Forchel, A.; Hawrylak, Paweł; Hinzer, Karin; Korkusiński, Marek; Fafard, S.; Wasilewski, Z. R.; Reinecke, T. L.; Lyanda-Geller, Yuli

doi:10.1117/12.514621

Cited by 37 publications

(54 citation statements)

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“…Recent work indicates that an exchange energy of 10 −4 eV or larger is easily achievable with vertically stacked quantum dots. 69,75,76 At the same time, the large energy spacing between the ground and the excited orbital ͑10 −2 -10 −1 eV͒ of the quantum dots ensures that the electron qubit stays in the ground orbital while the two-qubit operation is conducted. 70 This result shows that the electronnuclear spin interaction does not hinder quantum-dot based quantum computer architectures from being scalable even in the presence of inhomogeneous environments causing inhomogeneous hyperfine splittings.…”

Section: Discussionmentioning

confidence: 99%

Effect of electron-nuclear spin interactions for electron-spin qubits localized in InGaAs self-assembled quantum dots

Lee

Allmen

Oyafuso

et al. 2005

Journal of Applied Physics

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Lee, Seungwon; von Allmen, Paul; Oyafuso, Fabiano; and Klimeck, Gerhard, "Effect of electron-nuclear spin interactions for electronspin qubits localized in InGaAs self-assembled quantum dots" (2005 The effect of electron-nuclear spin interactions on qubit operations is investigated for a qubit represented by the spin of an electron localized in an InGaAs self-assembled quantum dot. The localized electron wave function is evaluated within the atomistic tight-binding model. The electron Zeeman splitting induced by the electron-nuclear spin interaction is estimated in the presence of an inhomogeneous environment characterized by a random nuclear spin configuration, by the dot-size distribution, alloy disorder, and interface disorder. Due to these inhomogeneities, the electron Zeeman splitting varies from one qubit to another by the order of 10 −6 , 10 −6 , 10 −7 , and 10 −9 eV, respectively. Such fluctuations cause errors in exchange operations due to the inequality of the Zeeman splitting between two qubits. However, the error can be made lower than the quantum error threshold if an exchange energy larger than 10 −4 eV is used for the operation. This result shows that the electron-nuclear spin interaction does not hinder quantum-dot based quantum computer architectures from being scalable even in the presence of inhomogeneous environments.

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Section: Discussionmentioning

confidence: 99%

Effect of electron-nuclear spin interactions for electron-spin qubits localized in InGaAs self-assembled quantum dots

Lee

Allmen

Oyafuso

et al. 2005

Journal of Applied Physics

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“…It includes devices for optoelectronics, quantum computing, and quantum cryptography. [1][2][3] In particular, one of the very important issues and challenges is the tuning of the emission wavelength of InAs/ GaAs quantum dots to 1.3 and 1.55 m for developing GaAs based QD laser diodes for telecommunication applications. 4,5 Most of the applications concern quantum dots fabricated in the so-called Stranski-Krastanov process.…”

Section: Introductionmentioning

confidence: 99%

Wetting layer states of InAs∕GaAs self-assembled quantum dot structures: Effect of intermixing and capping layer

Sęk

Ryczko

Motyka

et al. 2007

Journal of Applied Physics

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Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publicationCitation for published version (APA): Sek, G., Ryczko, K., Motyka, M., Andrzejewski, J., Wysocka, K., Misiewicz, J., ... Patriarche, G. (2007). Wetting layer states of InAs/GaAs self-assembled quantum dot structures. Effect of intermixing and capping layer. Journal of Applied Physics, 101(6), 063539-1/7. [063539]. DOI: 10.1063/1.2711146 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. The authors present a modulated reflectivity study of the wetting layer ͑WL͒ states in molecular beam epitaxy grown InAs/ GaAs quantum dot ͑QD͒ structures designed to emit light in the 1.3-1.5 m range. A high sensitivity of the technique has allowed the observation of all optical transitions in the QD system, including low oscillator strength transitions related to QD ground and excited states, and the ones connected with the WL quantum well ͑QW͒. The support of WL content profiles, determined by transmission electron microscopy, has made it possible to analyze in detail the real WL QW confinement potential which was then used for calculating the optical transition energies. We could conclude that in spite of a very effective WL QW intermixing, mainly due to the Ga-In exchange process ͑causing the reduction of the maximum indium content in the WL layer to about 35% from nominally deposited InAs͒, the transition energies remain almost unaffected. The latter effect could be explained in effective mass envelope function calculations taking into account the intermixing of the QW interfaces described within the diffusion model. We have followed the WL-...

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“…The ability to manipulate this coupling in a controllable way while preserving the quantum coherence is important for the development of various device applications of coupled QDs ͑CQDs͒ in spintronics, 5 optoelectronics, 6 photovoltaics, 7 and quantum information technologies. 4,8,9 In electrostatically confined CQDs, where dots are usually laterally coupled, accurate control can be achieved through the gate voltage or perpendicular magnetic fields. 10 In vertically CQDs however the degree of control achieved to date is comparatively lower.…”

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confidence: 99%

“…͓DOI: 10.1063/1.3040058͔ When two semiconductor quantum dots ͑QDs͒ are placed close to each other, the atomiclike states of the individual dots hybridize, forming bonding ͑nodeless͒ and antibonding ͑noded͒ molecularlike states, in analogy with diatomic molecules. [1][2][3][4] The energy splitting between the bonding and antibonding states is given by tunnel coupling strength, i.e., the overlap between the atomiclike orbitals in the interdot barrier. The ability to manipulate this coupling in a controllable way while preserving the quantum coherence is important for the development of various device applications of coupled QDs ͑CQDs͒ in spintronics, 5 optoelectronics, 6 photovoltaics, 7 and quantum information technologies.…”

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confidence: 99%

“…[1][2][3][4] The energy splitting between the bonding and antibonding states is given by tunnel coupling strength, i.e., the overlap between the atomiclike orbitals in the interdot barrier. The ability to manipulate this coupling in a controllable way while preserving the quantum coherence is important for the development of various device applications of coupled QDs ͑CQDs͒ in spintronics, 5 optoelectronics, 6 photovoltaics, 7 and quantum information technologies.…”

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Tuning the tunnel coupling of quantum dot molecules with longitudinal magnetic fields

Climente

2008

Applied Physics Letters

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We show that the energy splitting between the bonding and antibonding molecular states of holes in vertically stacked quantum dots can be tuned using longitudinal magnetic fields. With increasing field, the energy splitting first decreases to zero and then to negative values, which implies a bonding-to-antibonding ground state transition. This effect is a consequence of the enhancement of the valence band spin-orbit interaction induced by the magnetic field; it provides a flexible mechanism to switch the molecular ground state from bonding to antibonding. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.3040058͔ When two semiconductor quantum dots ͑QDs͒ are placed close to each other, the atomiclike states of the individual dots hybridize, forming bonding ͑nodeless͒ and antibonding ͑noded͒ molecularlike states, in analogy with diatomic molecules. [1][2][3][4] The energy splitting between the bonding and antibonding states is given by tunnel coupling strength, i.e., the overlap between the atomiclike orbitals in the interdot barrier. The ability to manipulate this coupling in a controllable way while preserving the quantum coherence is important for the development of various device applications of coupled QDs ͑CQDs͒ in spintronics, 5 optoelectronics, 6 photovoltaics, 7 and quantum information technologies. 4,8,9 In electrostatically confined CQDs, where dots are usually laterally coupled, accurate control can be achieved through the gate voltage or perpendicular magnetic fields. 10 In vertically CQDs however the degree of control achieved to date is comparatively lower. In these structures, the potential barrier height is fixed by the band offset between the QD and the surrounding matrix materials. By increasing the barrier length, one can reduce the tunnel coupling and hence the splitting between bonding and antibonding levels ⌬ BAB , 9,11,12 but this can only be done during the sample growth. A more flexible method is the use of transverse magnetic fields that enable one to tune the tunnel coupling of a sample after its growth. [13][14][15] Yet, large transverse fields may be required to obtain a sizable reduction in ⌬ BAB because the vertical confinement of these structures is usually strong and the axial symmetry of the structure is broken by the field. The latter effect activates otherwise forbidden transitions that are undesirable for optical manipulation and nondestructive measurements. 16 The use of longitudinal magnetic fields would clearly be more desirable, but it has been shown that they barely affect the molecular coupling of electrons except in some particular setups, such as asymmetric coupled quantum rings. 17 In this work we show that an unprecedented degree of control on the tunnel coupling of vertically CQDs can be achieved with longitudinal magnetic fields if instead of using conduction electrons, one uses valence holes. The method can be applied to regular self-assembled or lithographically grown QDs and is particularly suitable for quantum information devices, where holes may outperfor...

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<title>Entangled exciton states in quantum dot molecules</title>

Cited by 37 publications

References 1 publication

Effect of electron-nuclear spin interactions for electron-spin qubits localized in InGaAs self-assembled quantum dots

Effect of electron-nuclear spin interactions for electron-spin qubits localized in InGaAs self-assembled quantum dots

Wetting layer states of InAs∕GaAs self-assembled quantum dot structures: Effect of intermixing and capping layer

Tuning the tunnel coupling of quantum dot molecules with longitudinal magnetic fields

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