Spin and orbital structure of the first six holes in a silicon metal-oxide-semiconductor quantum dot

Liles, S. D.; Li, R.; Yang, C. H.; Hudson, Fay E.; Veldhorst, Menno; Dzurak, A. S.; Hamilton, A. R.

doi:10.1038/s41467-018-05700-9

Cited by 57 publications

(43 citation statements)

References 44 publications

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“…The difference in g-factors between the two dots is likely caused by slightly different hole fillings and thus quantum dot orbitals. Due to the influence of spin-orbit coupling, a strong orbital dependence of the effective g-factor is typically expected in hole quantum dots [17,28]. Furthermore the effective g-factor can be tuned electrically as a direct result of the SOC [29] (see e.g.…”

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confidence: 99%

Fast two-qubit logic with holes in germanium

Hendrickx

Franke

Sammak

et al. 2020

Nature

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The promise of quantum computation with quantum dots has stimulated widespread research. Still, a platform that can combine excellent control with fast and high-fidelity operation is absent. Here, we show single and two-qubit operations based on holes in germanium. A high degree of control over the tunnel coupling and detuning is obtained by exploiting quantum wells with very low disorder and by working in a virtual gate space. Spin-orbit coupling obviates the need for microscopic elements and enables rapid qubit control with Rabi frequencies exceeding 100 MHz and a singlequbit fidelity of 99.3 %. We demonstrate fast two-qubit CX gates executed within 75 ns and minimize decoherence by operating at the charge symmetry point. Planar germanium thus matured within one year from a material that can host quantum dots to a platform enabling two-qubit logic, positioning itself as a unique material to scale up spin qubits for quantum information.Gate-defined quantum dots were recognized early on as a promising platform for quantum information [1] and a plethora of materials stacks has been investigated as host material. Initial research mainly focused on the low disorder semiconductor gallium arsenide [2,3]. Steady progress in the control and understanding of this system culminated in the initial demonstration and optimization of spin qubit operations [4,5] and the realization of rudimentary analog quantum simulations [6]. However, the omnipresent hyperfine interactions in group III-V materials seriously deteriorate the spin coherence, despite attempts to mitigate this by nuclear polarization [7]. Drastic improvements to the coherence times could be achieved by switching to the group IV semiconductor silicon, in particular when defining spin qubits in isotopically purified host crystal with vanishing concentrations of nonzero nuclear spin [8]. This enabled single qubit rotations with fidelities beyond 99.9% [9] and the execution of two-qubit logic gates with fidelities up to 98% [10-13], underlining the potential of spin qubits for quantum computation. Nevertheless, quantum dots in silicon are often formed at unintended locations and control over the tunnel coupling determining the strength of two-qubit interactions is limited. Moreover, the absence of a sizable spin-orbit coupling for electrons requires the inclusion of microscopic components such as onchip striplines or nanomagnets close to each qubit, which seriously complicates the design of large and dense 2D-structures. This, combined with the limited control over the location and coupling of the dots, remains an outstanding challenge for the scalability of these systems and a platform that can overcome these limitations would be highly desirable. * These two authors contributed equally to this work Hole states in semiconductors typically exhibit strong spinorbit coupling, which has enabled the demonstration of fast single qubit rotations [14,15] and additionally, unlike electrons, holes do not suffer from nearby valley states. In silicon, unfavorable band alignment...

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confidence: 99%

Fast two-qubit logic with holes in germanium

Hendrickx

Franke

Sammak

et al. 2020

Nature

Self Cite

275

283

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“…Furthermore, achieving these assets on a single-hole spin demonstrates full control over the materials system and allows to tune the quantum dot occupancy at will, optimising the different qubit properties. Moreover, the ability to study a platform at the single-particle level would provide great insight into its physical nature, crucial for holes that originate from a more-complicated band structure than electrons 30,31 .…”

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confidence: 99%

A single-hole spin qubit

et al. 2020

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Qubits based on quantum dots have excellent prospects for scalable quantum technology due to their compatibility with standard semiconductor manufacturing. While early research focused on the simpler electron system, recent demonstrations using multi-hole quantum dots illustrated the favourable properties holes can offer for fast and scalable quantum control. Here, we establish a single-hole spin qubit in germanium and demonstrate the integration of single-shot readout and quantum control. We deplete a planar germanium double quantum dot to the last hole, confirmed by radio-frequency reflectrometry charge sensing. To demonstrate the integration of single-shot readout and qubit operation, we show Rabi driving on both qubits. We find remarkable electric control over the qubit resonance frequencies, providing great qubit addressability. Finally, we analyse the spin relaxation time, which we find to exceed one millisecond, setting the benchmark for hole quantum dot qubits. The ability to coherently manipulate a single hole spin underpins the quality of strained germanium and defines an excellent starting point for the construction of quantum hardware.

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“…This enables long spin coherence times in comparison to III-V semiconductors. In purified 28 Si silicon, electron spin coherence times up to a few seconds have been achieved [2,9,10]. Electrons in silicon also experience weak spin-orbit interaction so that their spins are largely immune to charge noise [11].…”

Section: Introductionmentioning

confidence: 99%

“…Despite these promising properties, hole spins in Si QDs have remained mostly unstudied. Single-hole occupation was reported in silicon nanowires [27] and only very recently in planar silicon QDs [28].…”

Section: Introductionmentioning

confidence: 99%

Ambipolar charge sensing of few-charge quantum dots

et al. 2020

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We demonstrate few-charge occupation of electron and hole quantum dots in silicon via charge sensing. We have fabricated quantum dot (QD) devices in a silicon metal-oxide-semiconductor heterostructure comprising a single-electron transistor next to a single-hole transistor. Both QDs can be tuned to simultaneously sense charge transitions of the other one. We further detect the few-electron and few-hole regimes in the QDs of our device by active charge sensing.

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Spin and orbital structure of the first six holes in a silicon metal-oxide-semiconductor quantum dot

Cited by 57 publications

References 44 publications

Fast two-qubit logic with holes in germanium

Fast two-qubit logic with holes in germanium

A single-hole spin qubit

Ambipolar charge sensing of few-charge quantum dots

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