Nuclear Spin Wave Quantum Register for a Single Rare-Earth Ion Qubit*

Optically addressable solid-state spins are a leading candidate to realise large-scale quantum networks. We explore single ¹⁷¹Yb ions in YVO₄ coupled to nanophotonic cavities as a network node architecture. These ions exhibit excellent coherence properties enabled by first order insensitivity of optical and spin transitions to electric and magnetic field noise [1].

In this talk we realise a quantum register for the ¹⁷¹Yb qubit using a spin-wave like collective excitation of the surrounding ⁵¹V nuclear spins [2]. This is enabled by a novel quantum control protocol using the magnetically insensitive ¹⁷¹Yb qubit transition, allowing for polarisation and manipulation of the nuclear register for quantum information storage, as well as for the creation of maximally entangled Bell states. Unlike conventional, disordered nuclear spin quantum memories, this approach is reproducible and deterministic, i.e., every ¹⁷¹Yb qubit accesses an identical register. In the future, the multi-node connectivity enabled by such registers will facilitate the exploration of single rare-earth ions doped into nuclear spin rich hosts as a platform for realising scalable quantum repeater networks.

[1] Kindem, Ruskuc et al. Nature, 580, 201 (2020)

[2] Ruskuc et al. https://arxiv.org/abs/2108.12723 (2021)