Substitutional nickel impurities in diamond: decoherence-free subspaces for quantum information processing

TL;DR

This study investigates substitutional nickel impurities in diamond, revealing their potential as controllable, decoherence-free qubits for quantum computing due to strain-tunable exchange interactions.

Contribution

It demonstrates that Ni impurities in diamond form a controllable two-electron system suitable for quantum information processing, a novel approach for solid-state qubits.

Findings

Nickel impurities have a spin-one ground state with electrons on Ni and neighboring carbons.

Exchange interaction is controllable via strain, enabling manipulation of spin states.

Ni impurity system can serve as a robust qubit for quantum computing.

Abstract

The electronic and magnetic properties of a neutral substitutional nickel (Ni$_s^0$) impurity in diamond are studied using density functional theory in the generalized gradient approximation. The spin-one ground state consists of two electrons with parallel spins, one located on the nickel ion in the $3d^9$ configuration and the other distributed among the nearest-neighbor carbons. The exchange interaction between these spins is due to $p-d$ hybridization and is controllable with compressive hydrostatic or uniaxial strain, and for sufficient strain the antiparallel spin configuration becomes the ground state. Hence, the Ni impurity forms a controllable two-electron exchange-coupled system that should be a robust qubit for solid-state quantum information processing.