Two-qubit couplings of singlet-triplet qubits mediated by one quantum state

Mehl, Sebastian; Bluhm, Hendrik; DiVincenzo, David P.

doi:10.1103/physrevb.90.045404

Cited by 42 publications

(53 citation statements)

References 54 publications

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“…We now turn to predictions of our model for the correlation function C χ defined in (16). Suppose that the nuclear configurations at the two times t p and t q are known, so that the corresponding LZ probabilities are also known.…”

Section: Correlations In S-t+ Sweepsmentioning

confidence: 99%

“…The coupling of the electrons to the underlying nuclear environment plays an important role in spintronics [1] and utilization of electron spins for quantum computation [2][3][4]. More generally, the interaction between a driven electron-spin qubit and its many-body environment leads to complex dynamical phenomena which are absent if the system is assumed to be at equilibrium with its environment [5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Thus, a qubit can be utilized as a probe for studying out-of-equilibrium physics in interacting quantum systems.…”

Section: Introductionmentioning

confidence: 99%

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Electron spin-flip correlations due to nuclear dynamics in driven GaAs double dots

et al. 2017

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We present experimental data and associated theory for correlations in a series of experiments involving repeated Landau-Zener sweeps through the crossing point of a singlet state and a spin aligned triplet state in a GaAs double quantum dot containing two conduction electrons, which are loaded in the singlet state before each sweep, and the final spin is recorded after each sweep. The experiments reported here measure correlations on time scales from 4 µs to 2 ms. When the magnetic field is aligned in a direction such that spin-orbit coupling cannot cause spin flips, the correlation spectrum has prominent peaks centered at zero frequency and at the differences of the Larmor frequencies of the nuclei, on top of a frequency-independent background. When the spin-orbit field is relevant, there are additional peaks, centered at the frequencies of the individual species. A theoretical model which neglects the effects of high-frequency charge noise correctly predicts the positions of the observed peaks, and gives a reasonably accurate prediction of the size of the frequency-independent background, but gives peak areas that are larger than the observed areas by a factor of two or more. The observed peak widths are roughly consistent with predictions based on nuclear dephasing times of the order of 60 µs. However, there is extra weight at the lowest observed frequencies, which suggests the existence of residual correlations on the scale of 2 ms. We speculate on the source of these discrepancies.

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Section: Correlations In S-t+ Sweepsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electron spin-flip correlations due to nuclear dynamics in driven GaAs double dots

et al. 2017

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“…2, 3, 5, 6) as done in Ref. [12,36]. A random component δE z parallel to the external magnetic field is considered as the main error contribution with typical values for uncorrected nuclear spin baths of 100 neV for GaAs QDs [37] and 3 neV in Si QDs [38], that correspond to magnetic fields of 5 mT and 25 µT, respectively.…”

Section: Hyperfine Interactionsmentioning

confidence: 99%

“…(7). The composite system of the two qubits, that is five electronic spins, is described by a nine-dimensional basis in the subspaces with total angular momentum equal to S = 1 2 , S z = 1 2 and S = 3 2 , S z = 1 2 obtained composing the one qubit states (12) and (7) with appropriate Clebsch-Gordan coefficients:…”

Section: Double Quantum Dot Singlet-triplet Qubit and Double Quantum mentioning

confidence: 99%

“…The double QD hybrid qubit [9] combines spin and charge and the qubit is realized with three electrons arranged in two QDs. For all of these architectures, protocols for the implementation of single and two-qubit gates have been proposed [10,11,12,13]. Also experiments have been realized in some cases ranging from the realization of single qubit gates to the two-qubit gates for the single spin qubit [14].…”

Section: Introductionmentioning

confidence: 99%

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Controlled-NOT gate sequences for mixed spin qubit architectures in a noisy environment

Ferraro

Fanciulli

Michielis

2017

Quantum Inf Process

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Explicit controlled-NOT gate sequences between two qubits of different types are presented in view of applications for large-scale quantum computation. Here, the building blocks for such composite systems are qubits based on the electrostatically confined electronic spin in semiconductor quantum dots. For each system the effective Hamiltonian models expressed by only exchange interactions between pair of electrons are exploited in two different geometrical configurations. A numerical genetic algorithm that takes into account the realistic physical parameters involved is adopted. Gate operations are addressed by modulating the tunneling barriers and the energy offsets between different couple of quantum dots. Gate infidelities are calculated considering limitations due to unideal control of gate sequence pulses, hyperfine interaction and charge noise.

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Jellybean Quantum Dots in Silicon for Qubit Coupling and On‐Chip Quantum Chemistry

et al. 2023

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The small size and excellent integrability of silicon metal–oxide–semiconductor (SiMOS) quantum dot spin qubits make them an attractive system for mass‐manufacturable, scaled‐up quantum processors. Furthermore, classical control electronics can be integrated on‐chip, in‐between the qubits, if an architecture with sparse arrays of qubits is chosen. In such an architecture qubits are either transported across the chip via shuttling or coupled via mediating quantum systems over short‐to‐intermediate distances. This paper investigates the charge and spin characteristics of an elongated quantum dot—a so‐called jellybean quantum dot—for the prospects of acting as a qubit–qubit coupler. Charge transport, charge sensing, and magneto‐spectroscopy measurements are performed on a SiMOS quantum dot device at mK temperature and compared to Hartree–Fock multi‐electron simulations. At low electron occupancies where disorder effects and strong electron–electron interaction dominate over the electrostatic confinement potential, the data reveals the formation of three coupled dots, akin to a tunable, artificial molecule. One dot is formed centrally under the gate and two are formed at the edges. At high electron occupancies, these dots merge into one large dot with well‐defined spin states, verifying that jellybean dots have the potential to be used as qubit couplers in future quantum computing architectures.

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Two-qubit couplings of singlet-triplet qubits mediated by one quantum state

Cited by 42 publications

References 54 publications

Electron spin-flip correlations due to nuclear dynamics in driven GaAs double dots

Electron spin-flip correlations due to nuclear dynamics in driven GaAs double dots

Controlled-NOT gate sequences for mixed spin qubit architectures in a noisy environment

Jellybean Quantum Dots in Silicon for Qubit Coupling and On‐Chip Quantum Chemistry

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