Highly tuneable hole quantum dots in Ge-Si core-shell nanowires

Brauns, Matthias; Ridderbos, Joost; Li, Ang; Wiel, Wilfred G. van der; Bakkers, Erik P. A. M.; Zwanenburg, Floris A.

doi:10.1063/1.4963715

Cited by 28 publications

(29 citation statements)

References 31 publications

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“…These experiments demonstrated the possibility to control the tunnel coupling, albeit in the multi-hole regime. Further advances in material quality 181 enabled quantum dots with an increased tuning capability 197 allowing to define single, double and triple QDs in Ge/Si NWs (Fig. 4a), with a low hole occupation number 193 (Fig.…”

Section: Nanowiresmentioning

confidence: 99%

The germanium quantum information route

et al. 2020

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Section: Nanowiresmentioning

confidence: 99%

The germanium quantum information route

et al. 2020

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“…c) Same data as b) plotted versus n, only positive V SD is shown. The vertical dashed gray lines show integers of n which can be matched with the MAR peaks up to n = 6. semiconducting island can be host to a single few-hole quantum dot [44] and that highly-tunable normal-state devices can be host to dots of length l > 400 nm [38]. By increasing the Al-nanowire interface transparencies, fully ballistic junctions could therefore be realised with lengths up to a few hundred nanometer.…”

Section: Junction Characteristicsmentioning

confidence: 99%

Multiple Andreev reflections and Shapiro steps in a Ge-Si nanowire Josephson junction

Ridderbos

Brauns

et al. 2019

Phys. Rev. Materials

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We present a Josephson junction based on a Ge-Si core-shell nanowire with transparent superconducting Al contacts, a building block which could be of considerable interest for investigating Majorana bound states, superconducting qubits and Andreev (spin) qubits. We demonstrate the dc Josephson effect in the form of a finite supercurrent through the junction, and establish the ac Josephson effect by showing up to 23 Shapiro steps. We observe multiple Andreev reflections up to the sixth order, indicating that charges can scatter elastically many times inside our junction, and that our interfaces between superconductor and semiconductor are transparent and have low disorder. arXiv:1908.07579v1 [cond-mat.mes-hall]

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“…Figure 1 a shows a scanning electron micrograph of the device comprising five gates beneath a Ge/Si core/shell nanowire [8,32,33]. A depletion-mode few-hole double quantum dot (DQD) is formed inside the nanowire by positively biasing the five bottom gates.…”

Section: Setup and Measurement Techniquesmentioning

confidence: 99%

Ultrafast Hole Spin Qubit with Gate-Tunable Spin-Orbit Switch

Froning,

Camenzind,

van der Molen

et al. 2020

Preprint

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A key challenge in quantum computation is the implementation of fast and local qubit control while simultaneously maintaining coherence [1]. Qubits based on hole spins offer, through their strong spin-orbit interaction, a way to implement fast quantum gates [2][3][4][5]. Strikingly, for hole spins in one-dimensional germanium and silicon devices, the spin-orbit interaction has been predicted to be exceptionally strong yet highly tunable with gate voltages. Such electrical control would make it possible to switch on demand between qubit idling and manipulation modes [6]. Here, we demonstrate ultrafast and universal quantum control of a hole spin qubit in a germanium/silicon core/shell nanowire [7,8], with Rabi frequencies of several hundreds of megahertz, corresponding to spin-flipping times as short as ∼ 1 ns -a new record for a single-spin qubit. Next, we show a large degree of electrical control over the Rabi frequency, Zeeman energy, and coherence time -thus implementing a switch toggling from a rapid qubit manipulation mode to a more coherent idling mode. We identify an exceptionally strong but gate-tunable spin-orbit interaction as the underlying mechanism, with a short associated spin-orbit length that can be tuned over a large range down to 3 nm for holes of heavy-hole mass. Our work demonstrates a spin-orbit qubit switch and establishes hole spin qubits defined in one-dimensional germanium/silicon nanostructures as a fast and highly tunable platform for quantum computation.

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Highly tuneable hole quantum dots in Ge-Si core-shell nanowires

Cited by 28 publications

References 31 publications

The germanium quantum information route

The germanium quantum information route

Multiple Andreev reflections and Shapiro steps in a Ge-Si nanowire Josephson junction

Ultrafast Hole Spin Qubit with Gate-Tunable Spin-Orbit Switch

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