Single, double, and triple quantum dots in Ge/Si nanowires

Froning, Florian; Rehmann, Mirko K.; Ridderbos, Joost; Brauns, Matthias; Zwanenburg, Floris A.; Li, A.; Bakkers, Erik P. A. M.; Zumbühl, Dominik M.; Braakman, Floris

doi:10.1063/1.5042501

Cited by 46 publications

(40 citation statements)

References 34 publications

(43 reference statements)

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“…These systems benefit from an even stronger Rashba type of SOI that relies on the HH-LH mixing and is not suppressed by the fundamental band gap [32,33]. In agreement with recent experiments [15,17,[34][35][36][37][38][39][40][41], Si and Ge/Si core/shell nanowires (NWs) are particularly promising platforms for such low-dimensional hole systems. Remarkably, these NWs and QDs therein can be formed with a complementary metal-oxide-semiconductor compatible fabrication process [17,36,38,42,43], which indicates an exceptional scalability.…”

Section: Introductionsupporting

confidence: 76%

“…Furthermore, many of the recent experimental setups seem to be invariant under reflection with respect to a certain plane, e.g., the plane being perpendicular to the plunger gates in Refs. [40,81]. Since the orientation of the magnetic field is usually tunable via a two-or threedimensional vector magnet, the study of anisotropic effects is well within the reach of state-of-the-art experiments.…”

Section: Discussionmentioning

confidence: 99%

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Exchange interaction of hole-spin qubits in double quantum dots in highly anisotropic semiconductors

Hetényi

Kloeffel

Loss

2020

Phys. Rev. Research

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We study the exchange interaction between two hole-spin qubits in a double quantum dot setup in a silicon nanowire in the presence of magnetic and electric fields. Based on symmetry arguments we show that there exists an effective spin that is conserved even in highly anisotropic semiconductors, provided that the system has a twofold symmetry with respect to the direction of the applied magnetic field. This finding facilitates the definition of qubit basis states and simplifies the form of exchange interaction for two-qubit gates in coupled quantum dots. If the magnetic field is applied along a generic direction, cubic anisotropy terms act as an effective spin-orbit interaction introducing novel exchange couplings even for an inversion symmetric setup. Considering the example of a silicon nanowire double dot, we present the relative strength of these anisotropic exchange interaction terms and calculate the fidelity of the √ SWAP gate. Furthermore, we show that the anisotropyinduced spin-orbit effects can be comparable to that of the direct Rashba spin-orbit interaction for experimentally feasible electric field strengths.

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Section: Introductionsupporting

confidence: 76%

Section: Discussionmentioning

confidence: 99%

Exchange interaction of hole-spin qubits in double quantum dots in highly anisotropic semiconductors

Hetényi

Kloeffel

Loss

2020

Phys. Rev. Research

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“…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. 4d).…”

Section: Nanowiresmentioning

confidence: 99%

“…This large anisotropy follows from an almost vanishing g-factor (g * min = 0.2) along the NW axis. Pauli spin blockade can elucidate the spin-flip mechanisms through the behaviour of the leakage current as a function of magnetic field 193,199,200 .…”

Section: Nanowiresmentioning

confidence: 99%

The germanium quantum information route

et al. 2020

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“…More recently, hole spins in group-IV materials have gained attention as a platform for quantum information processing [19][20][21][22] . In particular, hole states in germanium can provide a high degree of quantum dot tunability [23][24][25] , fast and all-electrical driving 20,21 and Ohmic contacts to superconductors for hybrids 26,27 . These experiments culminated in the recent demonstration of full two-qubit logic 21 .…”

mentioning

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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Single, double, and triple quantum dots in Ge/Si nanowires

Cited by 46 publications

References 34 publications

Exchange interaction of hole-spin qubits in double quantum dots in highly anisotropic semiconductors

Exchange interaction of hole-spin qubits in double quantum dots in highly anisotropic semiconductors

The germanium quantum information route

A single-hole spin qubit

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