Abstract
Interaction with nuclear spins leads to decoherence and information loss in solid-state electron-spin qubits. One particular, ineradicable source of electron decoherence arises from decoherence of the nuclear spin bath, driven by nuclear–nuclear dipolar interactions. Owing to its many-body nature nuclear decoherence is difficult to predict, especially for an important class of strained nanostructures where nuclear quadrupolar effects have a significant but largely unknown impact. Here, we report direct measurement of nuclear spin bath coherence in individual self-assembled InGaAs/GaAs quantum dots: spin-echo coherence times in the range 1.2–4.5 ms are found. Based on these values, we demonstrate that strain-induced quadrupolar interactions make nuclear spin fluctuations much slower compared with lattice-matched GaAs/AlGaAs structures. Our findings demonstrate that quadrupolar effects can potentially be used to engineer optically active III-V semiconductor spin-qubits with a nearly noise-free nuclear spin bath, previously achievable only in nuclear spin-0 semiconductors, where qubit network interconnection and scaling are challenging.
Highlights
Interaction with nuclear spins leads to decoherence and information loss in solid-state electron-spin qubits
It is predicted that large nuclear quadrupolar interactions (QIs) present in strained self-assembled dots[13] can suppress the nuclear flip-flops resulting in extended electron spin coherence[14]
We probe nuclear coherence by measuring spin-echo decay times T2, which are found to be a factor of B5 longer compared with lattice-matched GaAs/AlGaAs structures—direct evidence of nuclear spin flip-flop suppression induced by inhomogeneous QI
Summary
Interaction with nuclear spins leads to decoherence and information loss in solid-state electron-spin qubits. We report direct measurement of nuclear spin bath coherence in individual self-assembled InGaAs/GaAs quantum dots: spin-echo coherence times in the range 1.2–4.5 ms are found Based on these values, we demonstrate that strain-induced quadrupolar interactions make nuclear spin fluctuations much slower compared with latticematched GaAs/AlGaAs structures. The unusual behaviour of arsenic is explained by additional inhomogeneous QI arising from random alloy mixing of gallium and indium atoms[18] Such atomic-scale disorder opens a new prospect for using the excellent properties of III–V QDs to build nuclear-spin-noise free solid-state qubits: this can be done without resorting to materials with zero nuclear spin (for example, isotopically pure 28Si and 12C)[19,20,21], which have inferior optical properties, hampering on-chip integration of a large number of qubits
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