Electrostatically defined quantum dots in a Si/SiGe heterostructure

Wild, Andreas; Sailer, Juergen; Nützel, J. F.; Abstreiter, G.; Ludwig, Stefan; Bougeard, Dominique

doi:10.1088/1367-2630/12/11/113019

Cited by 15 publications

(12 citation statements)

References 49 publications

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“…16 As a result, Si spin QC has emerged as an active subfield of modern condensed matter physics. Outstanding experimental progress in Si spin QC has been reported in the last few years in Si quantum dots (QDs), [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] and in donor-based architectures. [36][37][38][39][40][41][42][43][44][45][46][47][48] Theoretical research on Si QDs has also evolved at a brisk pace.…”

Section: Introductionmentioning

confidence: 99%

Coherent electrical rotations of valley states in Si quantum dots using the phase of the valley-orbit coupling

Culcer

2012

Phys. Rev. B

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A gate electric field has a small but non-negligible effect on the phase of the valley-orbit coupling in Si quantum dots. Finite interdot tunneling between valley eigenstates in a double quantum dot is enabled by a small difference in the phase of the valley-orbit coupling between the two dots, and it in turn allows controllable rotations of two-dot valley eigenstates at a level anticrossing. We present a comprehensive analytical discussion of this process, with estimates for realistic structures.

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Section: Introductionmentioning

confidence: 99%

Coherent electrical rotations of valley states in Si quantum dots using the phase of the valley-orbit coupling

Culcer

2012

Phys. Rev. B

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“…7,9,10 However, at present the realization of stable QDs in a two-dimensional electron gas (2DEG) at a modulation-doped Si/SiGe heterostructure is still challenging due to the problem of charge noise which cause sudden changes to the QD states. 11,12 To realize stable qubit operation it is necessary to characterize and reduce the charge noise in quantum point contacts (QPCs) which form tunnel junctions with the QD.…”

mentioning

confidence: 99%

Characterization and suppression of low-frequency noise in Si/SiGe quantum point contacts and quantum dots

Takeda

Obata

Fukuoka

et al. 2013

Applied Physics Letters

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We report on the effects of a global top gate on low-frequency noise in Schottky gate-defined quantum point contacts (QPCs) and quantum dots (QDs) in a modulation-doped Si/SiGe heterostructure. For a relatively large top gate voltage, the QPC current shows frequent switching with 1/f 2 Lorentzian type charge noise. As the top gate voltage is decreased, the QPC pinch-off voltage becomes less negative, and the 1/f 2 noise becomes rapidly suppressed in a homogeneous background 1/f noise. We apply this top-gating technique to double QDs to stabilize the charge state for the electron number down to zero.Coherent control of single electron spin in solids aiming towards the realization of fundamental devices for quantum computation has been performed extensively in GaAs 1-6 and more recently in Si 7,8 as well. Si quantum dots (QDs) are one of the most promising candidates for implementing scalable spin quantum bit (qubit) systems because of the long coherence time due to weak spinorbit and hyperfine interactions. Recent experiments on Si QDs have shown the relaxation time T 1 and the dephasing time T * 2 much longer than those observed for GaAs QDs. 7,9,10 However, at present the realization of stable QDs in a two-dimensional electron gas (2DEG) at a modulation-doped Si/SiGe heterostructure is still challenging due to the problem of charge noise which cause sudden changes to the QD states. 11,12 To realize stable qubit operation it is necessary to characterize and reduce the charge noise in quantum point contacts (QPCs) which form tunnel junctions with the QD.Charge noise in gate-defined QPCs has been studied in detail for modulation-doped GaAs/AlGaAs heterostructures using techniques of asymmetrically biasing gates 13 , bias-cooling 14 , top gate biasing 15 and combinations of them. In Ref. 13 they observed charge noise caused by thermally activated trapping and detrapping by charge traps in local potential minima formed near the QPC channel when Schottky gates were occasionally biased to align the energy level of the charge trap and Fermi level of the QPC channel. On the other hand, in Ref. 14,15 , the charge noise is attributed to the electron tunneling between the surface and the 2DEG via charge traps in between. They observed strong charge noise reduction by application of bias-cooling or top gate technique which makes the operation voltage of the surface Schottky gate less negative. Then the tunnel rate of electrons from the

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“…[1][2][3][4] Recently, silicon QDs have attracted much attention due to their outstanding spin-related properties. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] Specifically, the hyperfine interaction can be reduced by isotopic purification. 25 The Dresselhaus spinorbit coupling (SOC) 26 is absent thanks to the bulk-inversion symmetry, and the SOC induced by the interface-inversion asymmetry (IIA) is rather weak.…”

mentioning

confidence: 99%

“…30,31 Nowadays, spin qubits in silicon single and double QDs have been actively investigated. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] In silicon single QDs, we have studied the singlet-triplet (ST) relaxation by explicitly including the electron-electron Coulomb interaction and the multivalley effect. Our results in the Voigt configuration agree quite well with the recent experiment by Xiao et al 16 Silicon double QDs, which have been proven very useful in exploiting the spin Coulomb blockade, 32 have also attracted much attention.…”

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confidence: 99%

Singlet-triplet relaxation in SiGe/Si/SiGe double quantum dots

Wang¹,

Wu²

2011

Journal of Applied Physics

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We study the singlet-triplet relaxation due to the spin-orbit coupling assisted by the electron-phonon scattering in two-electron SiGe/Si/SiGe double quantum dots in the presence of an external magnetic field in either Faraday or Voigt configuration. By explicitly including the electron-electron Coulomb interaction and the valley splitting induced by the interface scattering, we employ the exact-diagonalization method to obtain the energy spectra and the eigenstates. Then we calculate the relaxation rates with the Fermi golden rule. We find that the transition rates can be effectively tuned by varying the external magnetic field and the interdot distance. Especially in the vicinity of the anticrossing point, the transition rates show intriguing features. We also investigate the electric-field dependence of the transition rates, and find that the transition rates are almost independent of the electric field. This is of great importance in the spin manipulation since the lifetime remains almost the same during the change of the qubit configuration from $(1,1)$ to $(2,0)$ by the electric field.Comment: 9 pages, 8 figure

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Electrostatically defined quantum dots in a Si/SiGe heterostructure

Cited by 15 publications

References 49 publications

Coherent electrical rotations of valley states in Si quantum dots using the phase of the valley-orbit coupling

Coherent electrical rotations of valley states in Si quantum dots using the phase of the valley-orbit coupling

Characterization and suppression of low-frequency noise in Si/SiGe quantum point contacts and quantum dots

Singlet-triplet relaxation in SiGe/Si/SiGe double quantum dots

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