GHZ State Generation using an Optically Addressable Single Rare-Earth Ion Qubit*

Rare-earth ions doped into solid-state hosts are promising candidates for realizing quantum networks and studying quantum many-body dynamics. In particular, we have shown that single ¹⁷¹Yb ions in YVO₄ have highly coherent optical and spin transitions, and the surrounding ⁵¹V lattice nuclear spins (I=7/2) can be used as a quantum memory register by utilizing collective excitations of the ⁵¹V spin ensemble. In this work, we further demonstrate that a highly entangled nuclear GHZ state can be efficiently generated via coherent interactions between the ¹⁷¹Yb qubit and neighboring lattice nuclear spins, opening up new opportunities in quantum metrology and quantum device benchmarking. Specifically, we develop a control sequence to simultaneously manipulate four ⁵¹V spins by driving a ¹⁷¹Yb qubit to realize a controlled rotation gate for GHZ state preparation. The homogeneous one-to-all coupling between the ¹⁷¹Yb ion and ⁵¹V spins enables the efficient generation of a nuclear GHZ state, leading to a four-times enhanced parity oscillation frequency. Furthermore, we characterize and discuss the nuclear spin initialization fidelity and the GHZ state coherence time.