Erratum: Impurity effects on semiconductor quantum bits in coupled quantum dots [Phys. Rev. B<b>83</b>, 235322 (2011)]

Nguyen, Nga T. T.; Sarma, S. Das

doi:10.1103/physrevb.84.119904

Cited by 12 publications

(23 citation statements)

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“…The semiconductor samples used to create quantum dots invariably contain a number of charge impurity centers, perhaps 10 10 cm −2 in GaAs systems. 9 Even if the charge on these centers can be frozen to avoid switching noise, their presence inhibits access to the oneelectron-per-dot regime since the lowest energy states of the dot may be fragmented due to the roughened potential landscape. [10][11][12][13] This makes it difficult to find samples suitable for spin qubit realization.…”

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confidence: 99%

Screening of charged impurities with multielectron singlet-triplet spin qubits in quantum dots

et al. 2011

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Charged impurities in semiconductor quantum dots comprise one of the main obstacles to achieving scalable fabrication and manipulation of singlet-triplet spin qubits. We theoretically show that using dots that contain several electrons each can help to overcome this problem through the screening of the rough and noisy impurity potential by the excess electrons. We demonstrate how the desired screening properties turn on as the number of electrons is increased, and we characterize the properties of a double quantum dot singlet-triplet qubit for small odd numbers of electrons per dot. We show that the sensitivity of the multi-electron qubit to charge noise may be an order of magnitude smaller than that of the two-electron qubit.One of the most promising paths to scalable quantum computation is to use laterally defined double quantum dots (DQDs) in semiconductor heterostructures. The qubit is formed by the spin states of the two-electron DQD with total spin projection zero along the z axis. 1,2 Such a qubit is insensitive to spatially uniform magnetic field fluctuations, and, most importantly, amenable to fast electrical manipulation. 2,3 Recent experiments have made tremendous advances along these lines, demonstrating single-qubit initialization, arbitrary manipulation, and single-shot readout, all within a fraction of the coherence time of the qubit. 3-7 Preliminary steps toward an entangling two-qubit gate have also been reported. 8 In principle, successful completion of that program leaves the (admittedly enormous) challenge of scaling up to large numbers of qubits as the last remaining hurdle in the fabrication of a practical quantum computer.However, a practical issue has emerged which threatens to be a crippling impediment to continued rapid progress. The semiconductor samples used to create quantum dots invariably contain a number of charge impurity centers, perhaps 10 10 cm −2 in GaAs systems. 9 Even if the charge on these centers can be frozen to avoid switching noise, their presence inhibits access to the oneelectron-per-dot regime since the lowest energy states of the dot may be fragmented due to the roughened potential landscape. [10][11][12][13] This makes it difficult to find samples suitable for spin qubit realization. Furthermore, typically the impurities do introduce some switching noise, [14][15][16][17] so that even in samples in which the impurities are all far enough from the DQD that a two-electron singlettriplet qubit can be accessed, the interdot exchange energy is still subject to random fluctuation, leading to gate errors and decoherence. [18][19][20] This necessitates operating in a parameter regime such that the sensitivity of the exchange energy to the charge noise is minimized, a so-called "sweet spot". 21 In general, the charge noise problem is even more pernicious when performing twoqubit operations directly mediated by the Coulomb interaction, and one must again seek a sweet spot. 22,23 However, in practice, this strategy may not be sufficient since one typically cannot optimize ov...

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Screening of charged impurities with multielectron singlet-triplet spin qubits in quantum dots

et al. 2011

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“…The numerical results presented in this work refers to those corresponding to the parameters of GaAs: effective mass m * = 0.067m e , effective dielectric constant ε = 13.1, Bohr radius a * B = 10 nm and effective atomic unit of energy 1 Hartree * = 10.6 meV [48,42].…”

Section: Electronic Structure and Dynamicsmentioning

confidence: 99%

“…For example, confined electrons interact with spin nuclei through the hyperfine interaction leading, inevitably, to decoherence [3]. Even, having just one charged impurity could induce qubit decoherence if this impurity is dynamic and has a fluctuation time scale comparable to gate operation time scales [42]. Decoherence is a phenomenon that plays a central role in quantum information and its technological applications [53,54,55,56,57,58,59,60,61,62].…”

Section: Introductionmentioning

confidence: 99%

“…Recent works [42,43,44,45,46,47,48] studied the effects of having unintentional charged impurities in two-electron laterally coupled two-dimensional double quantum-dot systems. They analyzed the effects of quenched random-charged impurities on the singlet-triplet exchange coupling and spatial entanglement in two-electron double quantum-dots.…”

Section: Introductionmentioning

confidence: 99%

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Optimal control of a charge qubit in a double quantum dot with a Coulomb impurity

Coden

Romero

Ferrón

et al. 2017

Physica E: Low-dimensional Systems and Nanostructures

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Abstract. We study the efficiency of modulated laser pulses to produce efficient and fast charge localization transitions in a two-electron double quantum dot. We use a configuration interaction method to calculate the electronic structure of a quantum dot model within the effective mass approximation. The interaction with the electric field of the laser is considered within the dipole approximation and optimal control theory is applied to design high-fidelity ultrafast pulses in pristine samples. We assessed the influence of the presence of Coulomb charged impurities on the efficiency and speed of the pulses. A protocol based on a two-step optimization is proposed for preserving both advantages of the original pulse. The processes affecting the charge localization is explained from the dipole transitions of the lowest lying two-electron states, as described by a discrete model with an effective electron-electron interaction.

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“…In Ref. [27], the authors have studied the electron-electron correlations in many-electron single quantum dot (SQD) confined by parabolic potential in the presence of single magnetic ion and perpendicular magnetic field. They have obtained the energies and have studied the thermodynamic quantities such as heat capacity, the magnetization and the susceptibility.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Susceptibility of Coupled Double GaAs Quantum Dot in Magnetic Fields

Elsaid

Hijaz

2017

Acta Phys. Pol. A

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We calculate the magnetic susceptibility of two interacting electrons confined in a coupled double quantum dot presented in a magnetic field by solving the relative Hamiltonian using the combined variational and exact diagonalization methods. We have investigated the dependence of the magnetic susceptibility on temperature, magnetic field strength, confining frequency, and barrier height. The singlet-triplet transitions in the ground state of the quantum dot spectra and the corresponding jumps in the magnetic susceptibility curves have been shown. The comparisons show that our results are in very good agreement with reported works.

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Erratum: Impurity effects on semiconductor quantum bits in coupled quantum dots [Phys. Rev. B83, 235322 (2011)]

Cited by 12 publications

References 0 publications

Screening of charged impurities with multielectron singlet-triplet spin qubits in quantum dots

Screening of charged impurities with multielectron singlet-triplet spin qubits in quantum dots

Optimal control of a charge qubit in a double quantum dot with a Coulomb impurity

Magnetic Susceptibility of Coupled Double GaAs Quantum Dot in Magnetic Fields

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