Anomalous Zero-Field Splitting for Hole Spin Qubits in Si and Ge Quantum Dots

Hetényi, Bence; Bosco, Stefano; Loss, Daniel

doi:10.1103/physrevlett.129.116805

Cited by 7 publications

(3 citation statements)

References 74 publications

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“…[ 106,107 ] In contrast to electrons, the cubic‐in‐momentum Rashba SOC of holes can lead to a significant exchange anisotropy even at zero magnetic fields. [ 108 ] This anisotropy results in an anomalous energy splitting of the spin‐triplet state, which has been detected in Ge hut wire QDs with even hole occupation. [ 109 ] The anisotropic exchange interaction can induce systematic errors in two‐qubit gates based on isotropic interactions between tunnel‐coupled DQDs.…”

Section: Microscopic Physics Of Semiconductor Nanostructuresmentioning

confidence: 99%

Progress of Gate‐Defined Semiconductor Spin Qubit: Host Materials and Device Geometries

Liu,

Guan,

Luo

et al. 2024

Adv Funct Materials

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Quantum computing offers the potential to revolutionize information processing by exploiting the principles of quantum mechanics. Among the diverse quantum bit (qubit) technologies, silicon‐based semiconductor spin qubits have emerged as a promising contender due to their potential scalability and compatibility with existing semiconductor technologies. In this paper, the latest developments of spin qubits in gate‐defined semiconducting nanostructures made of silicon and germanium, starting from the basic properties of electron and hole states in group‐IV semiconductors, are reviewed. Specifically, various nanostructures that exploit their unique microscopic properties for qubit implementations, elaborating on the advances and challenges in experiments, are discussed. Strategies for enhancing qubit performance, such as designing new nanostructures and identifying suitable operating points, particularly those involving the valleys of electron qubits and the heavy‐hole–light‐hole mixing of hole qubits, are also highlighted. This comprehensive review thus provides valuable insights into the current state‐of‐the‐art in semiconductor quantum computing and suggests avenues for future research.

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Section: Microscopic Physics Of Semiconductor Nanostructuresmentioning

confidence: 99%

Progress of Gate‐Defined Semiconductor Spin Qubit: Host Materials and Device Geometries

Liu,

Guan,

Luo

et al. 2024

Adv Funct Materials

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“…In some cases a cubic SOI term becomes relevant, which requires to extend the perturbation theory to third order [88].…”

Section: Homogeneous Electric Field Limitmentioning

confidence: 99%

Enhanced orbital magnetic field effects in Ge hole nanowires

et al. 2022

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Hole semiconductor nanowires (NW) are promising platforms to host spin qubits and Majorana bound states for topological qubits because of their strong spin-orbit interactions (SOI). The properties of these systems depend strongly on the design of the cross section and on strain, as well as on external electric and magnetic fields. In this paper, we analyze in detail the dependence of the SOI and g factors on the orbital magnetic field. We focus on magnetic fields aligned along the axis of the NW, where orbital effects are enhanced and result in a renormalization of the effective g factor up to 400%, even at small values of magnetic field. We provide an exact analytical solution for holes in Ge NWs and we derive an effective low-energy model that enables us to investigate the effect of electric fields applied perpendicular to the NW. We also discuss in detail the role of strain, growth direction, and high-energy valence bands in different architectures, including Ge/Si core/shell NWs, gate-defined one-dimensional channels in planar Ge, and curved Ge quantum wells. By comparing NWs with different growth directions, we find that the isotropic approximation is well justified. Curved Ge quantum wells feature large effective g factors and SOI at low electric field, ideal for hosting Majorana bound states. In contrast, at strong electric field, these quantities are independent of the field, making hole spin qubits encoded in curved quantum wells to good approximation not susceptible to charge noise, and significantly boosting their coherence time.

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“…A key advantage of hole spins is their large and tunable spin-orbit interaction (SOI) enabling ultrafast all-electrical qubit operations [5][6][7][8][9][10][11], on-demand coupling to microwave photons [12][13][14], even without bulky micromagnets [15][16][17]. The large SOI of holes leads to interesting physical phenomena, such as electrically tunable Zeeman [6,[18][19][20][21][22] and hyperfine interactions [23][24][25], or exchange anisotropies at finite [26] and zero magnetic fields [27,28]. These effects can be leveraged for quantum information processing, e.g., to define operational sweet spots against noise [29][30][31][32][33][34]; to date their potential remains largely unexplored.…”

mentioning

confidence: 99%