Description
Coherently manipulated large ion crystals in a Penning trap are a promising candidate for near-term quantum simulation of complex many-body phenomena, and for quantum sensing to search for beyond-standard-model physics. However, their continuous rigid-body rotation has so far limited flexible local qubit control. Here, we demonstrate programmable site-selective spin control in large rotating crystals containing hundreds of ${}^{9}\text{Be}^{+}$ in a Penning trap. A tightly focused off-resonant laser beam is used to drive local $R_z$ phase rotations via differential AC Stark shifts. The radial position of the focused beam is controlled using an acousto-optic modulator (AOM), and a second AOM is used to rapidly modulate the laser power. This radial-plus-timing control combined with the continuous rotation of the crystal allows addressing arbitrary spins, akin to the protocols used to access arbitrary data on a hard disk drive. Through Ramsey-based characterisation, we show $R_z(\pi)$ gate fidelity of 94.6% and nearest-neighbour crosstalk of 1.2%. We use this capability to prepare spatially structured spin patterns, generating a biskyrmion spin texture in a single-layer crystal, and then extend the method to bilayer crystals where we perform layer-selective addressing operations. We further demonstrate dual-quadrature Ramsey sensing by imprinting a relative $\pi/2$ phase shift between spatial sub-ensembles, enabling simultaneous measurement of orthogonal spin components within a single experimental realisation. These results establish programmable local control in large rotating ion crystals, opening new routes for engineering spatially structured quantum states in multidimensional trapped-ion systems.
| I am the presenting author | Yes |
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