Electron–nuclear interaction in 13C nanotube double quantum dots

Churchill, Hugh; Bestwick, Andrew; Harlow, Jennifer; Kuemmeth, Ferdinand; Marcos, D. Crespo; Stwertka, C.; Watson, Susan K.; Marcus, C. M.

doi:10.1038/nphys1247

Cited by 168 publications

(268 citation statements)

References 30 publications

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“…Nevertheless, spin blockade has been observed previously in carbon nanotubes [10,11,13]. In the spin blockade regime, transitions between a (1,1) and (0,2) charge state directly depend on whether the (1,1) state is a singlet or triplet.…”

mentioning

confidence: 87%

“…Our measurements thus present a first quantitative analysis of the complex admittance of a double quantum dot. The demonstrated technique also provides the basis for a simple and fast detection scheme for charge and spin state readout in carbon nanotubes -a material with considerable potential for spin-based quantum information processing [8][9][10][11][12][13] -without the need for a separate charge detector [14].…”

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confidence: 99%

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Measuring the Complex Admittance of a Carbon Nanotube Double Quantum Dot

Chorley¹,

Wabnig²,

Penfold-Fitch³

et al. 2012

Phys. Rev. Lett.

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We investigate radio-frequency (rf) reflectometry in a tunable carbon nanotube double quantum dot coupled to a resonant circuit. By measuring the in-phase and quadrature components of the reflected rf signal, we are able to determine the complex admittance of the double quantum dot as a function of the energies of the single-electron states. The measurements are found to be in good agreement with a theoretical model of the device in the incoherent limit. Besides being of fundamental interest, our results present an important step forward towards non-invasive charge and spin state readout in carbon nanotube quantum dots. PACS numbers: 73.63.Fg, 73.63.Kv, 73.23.Hk, 03.67.Lx An important requirement in any quantum information processing scheme is fast manipulation and readout of the quantum system in which the quantum information is encoded. This requires an understanding of the response of the quantum system at finite frequencies which, in the case of an electronic device, involves an understanding of its complex admittance [1,2]. Of particular interest in the context of quantum information processing are double quantum dots which are widely used to define charge and spin qubits [3]. However, while double quantum dots have been investigated in detail over the last decade, experiments to measure and analyze their complex admittance have not yet been performed and this topic has only recently been addressed theoretically [4]. The admittance of quantum dots at finite frequencies is non-trivial as exemplified by recent experiments on single quantum dots [5,6]. The physics is even richer for double quantum dots as internal charge dynamics, i.e. charge transfer between the quantum dots, has to be taken into account. However, the dependence of the admittance on the internal charge dynamics also provides a route towards charge and spin state readout [7].In this work we present a detailed experimental study of the complex admittance of a carbon nanotube double quantum dot which is measured using rf reflectometry techniques. The measurements are compared with a theoretical model of the device where we use a density matrix approach to calculate the double quantum dot admittance. The good quantitative agreement between the experimental and theoretical results allows us to determine the effective conductance and susceptance of the double dot as a function of the energies of the single-electron states. Our measurements thus present a first quantitative analysis of the complex admittance of a double quantum dot. The demonstrated technique also provides the basis for a simple and fast detection scheme for charge and spin state readout in carbon nanotubes -a material with considerable potential for spin-based quantum information processing [8-13] -without the need for a separate charge detector [14].The device we consider is a carbon nanotube grown by chemical vapour deposition on degenerately doped Si ter- minated by 300 nm SiO 2 , see Fig. 1(a). The nanotube is contacted by Au source and drain electrodes which form the outer ...

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confidence: 87%

mentioning

confidence: 99%

Measuring the Complex Admittance of a Carbon Nanotube Double Quantum Dot

Chorley¹,

Wabnig²,

Penfold-Fitch³

et al. 2012

Phys. Rev. Lett.

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“…15 Recent experiments have shown that it is indeed possible to confine electrons in single [16][17][18][19] and double QDs ͑DQDs͒ in a CNT by means of electrostatic gates in cleanly grown small band-gap nanotubes. 5,15,20 The present study is motivated by these experimental results.…”

Section: Introductionmentioning

confidence: 95%

“…Spin qubits in carbon nanotubes 3,4 ͑CNTs͒ are believed to be even more robust due to the absence of hyperfine coupling in 12 C. 5 This is in contrast to GaAs QDs where the phase coherence suffers from hyperfine coupling due to the nuclei of the host crystal. However, CNTs pose other challenges and complications.…”

Section: Introductionmentioning

confidence: 99%

Spin-orbit effects in carbon-nanotube double quantum dots

Weiss¹,

Rashba²,

Kuemmeth³

et al. 2010

Phys. Rev. B

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We study the energy spectrum of symmetric double quantum dots in narrow-gap carbon nanotubes with one and two electrostatically confined electrons in the presence of spin-orbit and Coulomb interactions. Compared to GaAs quantum dots, the spectrum exhibits a much richer structure because of the spin-orbit interaction that couples the electron's isospin to its real spin through two independent coupling constants. In a single dot, both constants combine to split the spectrum into two Kramers doublets while the antisymmetric constant solely controls the difference in the tunneling rates of the Kramers doublets between the dots. For the two-electron regime, the detailed structure of the spin-orbit split energy spectrum is investigated as a function of detuning between the quantum dots in a 22-dimensional Hilbert space within the framework of a single-longitudinalmode model. We find a competing effect of the tunneling and Coulomb interaction. The former favors a left-right symmetric two-particle ground state while in the regime where the Coulomb interaction dominates over tunneling, a left-right antisymmetric ground state is found. As a result, ground states on both sides of the ͑11͒-͑02͒ degeneracy point may possess opposite left-right symmetry, and the electron dynamics when tuning the system from one side of the ͑11͒-͑02͒ degeneracy point to the other is controlled by three selection rules ͑in spin, isospin, and left-right symmetry͒. We discuss implications for the spin-dephasing and Pauli blockade experiments.

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“…Recently, several experiments have shown coherent manipulation of such spins for the purpose of spin-based quantum computation. [4][5][6][7][8][9][10] Enabled by advances in device technology, the number of quantum dots that can be accessed is quickly increasing from very few to many. 11,12 Up to date, all these quantum dots have been tuned by "hand."…”

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confidence: 99%

Computer-automated tuning of semiconductor double quantum dots into the single-electron regime

Baart

Eendebak

Reichl

et al. 2016

Applied Physics Letters

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We report the computer-automated tuning of gate-defined semiconductor double quantum dots in GaAs heterostructures. We benchmark the algorithm by creating three double quantum dots inside a linear array of four quantum dots. The algorithm sets the correct gate voltages for all the gates to tune the double quantum dots into the single-electron regime. The algorithm only requires (1) prior knowledge of the gate design and (2) the pinch-off value of the single gate T that is shared by all the quantum dots. This work significantly alleviates the user effort required to tune multiple quantum dot devices.

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Electron–nuclear interaction in 13C nanotube double quantum dots

Abstract: ). Electron-nuclear interaction in 13C nanotube double quantum dots. Nature Physics, 5(5), 321-326. https://doi.org

Cited by 168 publications

References 30 publications

Measuring the Complex Admittance of a Carbon Nanotube Double Quantum Dot

Measuring the Complex Admittance of a Carbon Nanotube Double Quantum Dot

Spin-orbit effects in carbon-nanotube double quantum dots

Computer-automated tuning of semiconductor double quantum dots into the single-electron regime

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