Scaling up a quantum register of dark electronic spins in diamond

Abstract

Electronic spin defects in the environment of an optically-active spin can be used to increase the size and hence the performance of solid-state quantum registers, especially for applications in quantum metrology and quantum communication. Previous works on multi-qubit electronic-spin registers in the environment of a Nitrogen-Vacancy (NV) center in diamond have only included spins directly coupled to the NV. As this direct coupling is limited by the spin coherence time, it significantly restricts the register's maximum attainable size. To address this problem, this thesis presents a scalable approach to map out and control a network of interacting environmental spins. We use this approach to characterize a spin network beyond the direct-coupling limit and exploit a weakly-coupled probe spin to mediate the transfer of spin polarization between the central NV and an environmental spin that is not directly coupled to it. We then demonstrate both detection and coherent control of this electronic spin outside the coherence limit of the central NV. Our work paves the way for engineering larger quantum spin registers with the potential to advance nanoscale sensing, enable correlated noise spectroscopy for error correction, and facilitate the realization of spin-chain quantum wires for quantum communication.