Measuring central-spin interaction with a spin bath by pulsed ENDOR: Towards suppression of spin diffusion decoherence

TL;DR

This paper demonstrates pulsed ENDOR techniques to characterize and suppress spin diffusion decoherence in bismuth donor spin qubits in silicon, achieving near-complete decoupling from the nuclear spin bath at optimal conditions.

Contribution

It introduces a method to quantify and significantly reduce spin bath-induced decoherence in silicon-based qubits using pulsed ENDOR and theoretical simulations.

Findings

Near-complete suppression of spin diffusion decoherence at optimal points

Weak anisotropic contributions to the decoherence mechanism

Divergences in coherence time are orientation-independent

Abstract

We present pulsed electron-nuclear double resonance (ENDOR) experiments which enable us to characterize the coupling between bismuth donor spin qubits in Si and the surrounding spin bath of 29Si impurities which provides the dominant decoherence mechanism (nuclear spin diffusion) at low temperatures (< 16 K). Decoupling from the spin bath is predicted and cluster correlation expansion simulations show near-complete suppression of spin diffusion, at optimal working points. The suppression takes the form of sharply peaked divergences of the spin diffusion coherence time, in contrast with previously identified broader regions of insensitivity to classical fluctuations. ENDOR data suggest that anisotropic contributions are comparatively weak, so the form of the divergences is largely independent of crystal orientation.