Generation and control of polarization-entangled photons from GaAs island quantum dots by an electric field

Ghali, Mohsen; Ohtani, K.; Ohno, Y.; Ohno, Hideo

doi:10.1038/ncomms1657

Cited by 86 publications

(85 citation statements)

References 32 publications

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“…This formula is expected from the classical "folded down" perturbation approach [1][2][3][4][5][6][7][11][12][13][14]16 . On the other hand, all data points of strained In(Ga)As/GaAs QDs exhibit a denominator ∆ HL that is effectively reduced by δ = 78.6 meV with respect to the class of unstrained GaAs QDs and fall then close to another curve:…”

Section: K · P Analysis Of Atomistic Microscopic Resultsmentioning

confidence: 99%

“…The two components of the valence band have diametrically opposed fundamental features (including different Bloch functions, pseudospin, type of optical transition, magnitude of effective masses and deformation potentials), so the extent of their quantum mechanical mixing underlies our fundamental understanding of the duality of a broad range of physical properties associated with hole in low-dimensional nanostructures. Specifically, such HH-LH mixing plays important roles in e.g., QDs 1 , including (i) tuning of the excitonic fine-structure splitting [2][3][4] which controls the fidelity of entangled photon pairs,…”

Section: Introductionmentioning

confidence: 99%

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Supercoupling between heavy-hole and light-hole states in nanostructures

2015

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The heavy-hole (HH) and light-hole (LH) components of the valence states in 3D bulk semiconductors can mix quantum mechanically as the dimensionality is reduced in forming 2D, 1D nanostructures and 0D quantum dots (QDs). This coupling controls the tuning of the excitonic fine structure splitting, provides an efficient channel for the spin coherence, and leads to polarization anisotropy of light emission, central to several quantum information schemes. Current understanding is that the mixing scales with the square of δV HL /∆ HL , where δV HL and ∆ HL are the coupling matrix elements of the crystal potential and the energy separation between the primary HH0 and LH0 states, respectively. We discuss two classes of HH-LH coupling mechanisms.First, coupling factors occurring through the numerator δV HL , referred to as "direct coupling", including the well-known (1) quantum confinement, (2) built-in strain, and (3) shape elongation, as well as three additional direct coupling mechanisms discussed here: (4) the intrinsic C 2v crystal field effect, (5) the local symmetry of the interface, and (6) the alloy disorder. We quantify these 6 direct HH-LH coupling effects by performing atomistic pseudopotential calculations on a range of strained and unstrained QDs of different morphologies. We find that in unstrained self-assembled QDs such as GaAs/AlGaAs effects (1)-(6) contribute 0%, 0%, 0%, 0%, 40%, and 60%, respectively, whereas in strained self-assembled QDs such as InGaAs/GaAs they contribute 0%, 0%, 78%, 0%, 8%, and 14%, respectively, to the direct HH-LH coupling δV HL . These relative contributions to direct HH-LH coupling differ significantly from what was previously believed.Second, we discover an unexpected HH-LH coupling that effectively reduces the denominator ∆ HL by the presence of a dense ladder of intermediate states between the HH0 and LH0 states (analogous to super-exchange in magnetism). Supercoupling amplifies and propagates the HH-LH interaction and is the dominant source of HH-LH mixing in strained nanostructures where ∆ HL is fairly large, so by the direct coupling mechanism alone δV HL /∆ HL would be expected to be rather small. Supercoupling explains a number of outstanding puzzles including the surprising fact that in strained (InAs/GaAs) QDs the mixing is very strong despite the fact that ∆ HL is large, and offers a new way to manipulate HH-LH mixing and hence associated properties in nanostructures.

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Section: K · P Analysis Of Atomistic Microscopic Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Supercoupling between heavy-hole and light-hole states in nanostructures

2015

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“…Typical values in InGaAs QDs range from almost zero to a few 100 µeV [32,33]. For schemes that are targeted at the preparation of the biexciton state, in order to subsequently initiate a decay cascade that creates entangled photon pairs [12,15,17] it is a necessary precondition to ideally have a vanishing exchange splitting [15,16,34,35]. Otherwise, a kind of which-path information would be introduced in the decay that prevents a high degree of entanglement [14,36].…”

Section: Quantum Dot Modelmentioning

confidence: 99%

The role of phonons for exciton and biexciton generation in an optically driven quantum dot

Reiter

Kuhn

Glässl

et al. 2014

J. Phys.: Condens. Matter

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Abstract. For many applications of semiconductor quantum dots in quantum technology a well controlled state preparation of the quantum dot states is mandatory. Since quantum dots are embedded in the semiconductor matrix, the interaction with phonons plays often a major role in the preparation process. In this review, we discuss the influence of phonons on three basically different optical excitation schemes which can be used for the preparation of exciton, biexciton, and superposition states: a resonant excitation leading to Rabi rotations in the excitonic system, an excitation with chirped pulses exploiting the effect of adiabatic rapid passage, and an off-resonant excitation giving rise to a phononassisted state preparation. We give an overview over experimental and theoretical results showing the role of the phonons and compare the performance of the schemes for state preparation.

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“…Correlated photon pairs are an important resource for quantum photonics that can be generated on-chip by quantum dots [4] or integrated nonlinear waveguides [5,6,14]. As well as being both compact and efficient, integrated photon pair sources have also shown unprecedented versatility in tailoring the properties of the generated twin-photon state through dispersion engineering and birefringence management, thereby establishing control over the spectral and polarization entanglement [15][16][17], photon bandwidths [18], and degree of non-degeneracy.…”

Section: Introductionmentioning

confidence: 99%

“…Mapping quantum photonic technologies into an integrated on-chip setting has become an important task for overcoming the severe stability and scalability limitations of bulk-optics implementations. Recent efforts have demonstrated on-chip quantum state generation [4][5][6], manipulation [7][8][9][10][11][12] and detection [13] across numerous material platforms including GaAs [6,11,13], silicon wire [5,12], silica-on-silicon [7,8,10], lithium niobate [14] and borosilicate glass [9].…”

Section: Introductionmentioning

confidence: 99%

Deterministic separation of arbitrary photon pair states in integrated quantum circuits

Marchildon

Helmy

2016

Laser & Photonics Reviews

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Entangled photon pairs generated within integrated devices must often be spatially separated for their subsequent manipulation in quantum circuits. Separation that is both deterministic and universal can in principle be achieved through anticoalescent two-photon quantum interference. However, such interference-facilitated pair separation (IFPS) has not been extensively studied in the integrated setting, where the strong polarization and wavelength dependencies of integrated couplers -as opposed to bulk-optics beamsplitters -can have important implications for performance beyond the identical-photon regime. This paper provides a detailed review of IFPS and examines how these dependencies impact separation fidelity and interference visibility. Focus is given to IFPS mediated by an integrated directional coupler. The analysis applies equally to both on-chip and in-fiber implementations, and can be expanded to other coupler architectures such as multimode interferometers. When coupler dispersion is present, the separation performance can depend on photon bandwidth, spectral entanglement, and the linearity of the dispersion. Under appropriate conditions, reduction in the separation fidelity due to loss of non-classical interference can be perfectly compensated for by classical wavelength demultiplexing effects. This work informs the design as well as the performance assessment of circuits for achieving universal photon pair separation for states with tunable arbitrary properties.

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Generation and control of polarization-entangled photons from GaAs island quantum dots by an electric field

Cited by 86 publications

References 32 publications

Supercoupling between heavy-hole and light-hole states in nanostructures

Supercoupling between heavy-hole and light-hole states in nanostructures

The role of phonons for exciton and biexciton generation in an optically driven quantum dot

Deterministic separation of arbitrary photon pair states in integrated quantum circuits

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