Electrical control of single hole spins in nanowire quantum dots

Abstract

Single electron spins in semiconductor quantum dots (QDs) are a versatile platform for quantum information processing, however controlling decoherence remains a considerable challenge. [1][2][3][4] Recently, hole spins have emerged as a promising alternative. Holes in III-V semiconductors have unique properties, such as strong spin-orbit interaction and weak coupling to nuclear spins, and therefore have potential for enhanced spin control 5-8 and longer coherence times 8-12 . Weaker hyperfine interaction has already been reported in self-assembled quantum dots using quantum optics techniques. 10-12 However, challenging fabrication has so far kept the promise of hole-spin-based electronic devices out of reach in conventional III-V heterostructures. 13 Here, we report gate-tuneable hole quantum dots formed in InSb nanowires. Using these devices we demonstrate Pauli spin blockade and electrical control of single hole spins. The devices are fully tuneable between hole and electron QDs, enabling direct comparison between the hyperfine interaction strengths, g-factors and spin blockade anisotropies in the two regimes.The development of viable quantum computation devices depends on the ability to preserve the coherence of quantum bits (qubits). 1 To date, most work in semiconductors has focused on using the spins of electrons as qubits. However, due to strong hyperfine coupling to the surrounding nuclear spin bath, electron spins experience rapid decoherence. [2][3][4] In contrast, the contact hyperfine interaction for hole spins is predicted to vanish due to the p-orbital symmetry of their Bloch wavefunction, leaving only the weaker dipole-dipole coupling. 9 However, a major technical challenge for investigating hole spins in gate-defined quantum dots has been that conventional p-doped quantum wells do not provide the required level of stability and tuneability. 13 An

Consequences of Spin-Orbit Coupling at the Single Hole Level: Spin-Flip Tunneling and the Anisotropic g Factor

“…The hole properties are traced to the amount of HH-LH subband mixing [12,13], which is related to the details of quantum confinement, strain, and the spin-orbit interaction. The early prediction of greatly reduced hyperfine interaction between hole and nuclear spins, and concomitant increased coherence times [14,15], were confirmed experimentally in systems with small HH-LH mixing realized as selfassembled dots (SADs) [16][17][18] or nanowires [19]. In this regime the strong anisotropy of the hole g-factor is expected [12].…”

Maximizing the purity of a qubit evolving in an anisotropic environment

“…45,46 In addition to optical coherent control of hole spins in self-assembled quantum dots, 39,41,47,48 there are several suggestions for electrical manipulation of hole spins. [49][50][51] Such electrical control has recently been demonstrated for hole spins in III-V nanowire quantum dots, 52 and coherence times have now been measured for hole spins in Ge-Si core-shell nanowire quantum dots. 53 The very recent achievement of the few-hole regime in lateral gated double-dot devices, 54 suggests that previous highly successful measurements performed for electron spins [55][56][57][58][59][60] can now be performed for hole spins, which show promise for much longer coherence times.…”

Generating and moving Dirac points in a two-dimensional deformed honeycomb lattice arrayed by coupled semiconductor quantum dots

“…[1][2][3] For example, the quasi-zero-dimensional semiconductor QD is called artificial atom and the planar coupled QDs array can be regarded as a two-dimensional (2D) artificial crystal. 4,5 In natural crystal, the rigid structure of the material determines the properties of the inside particles. However, the lattice parameters of the artificial crystal can be tuned, and consequently the electronic structure of system will be altered and manipulated.…”