Bryce B. Bullock

Penning ion traps as quantum platforms have primarily utilized global control and symmetric Dicke states for quantum simulation and sensing experiments. The introduction of local control greatly increases the power of the platform as a quantum simulator but is technically challenging due to the rapid rotation of the ion crystals. Here we use an ultraviolet-compatible spatial light modulator (SLM) to imprint programmable AC Stark shift patterns with different azimuthal symmetries and gradients that co-rotate with the ion crystals, demonstrating localized coherent control of single plane crystals with greater than 100 ions. Comparisons of the measured ion qubit populations with calculations from independent measurements of the applied AC Stark shift patterns show good agreement, validating the technique and providing a path, with a higher format SLM, for parallelizable, coherent individual ion addressing in Penning traps.

Penning traps have been used for performing quantum simulations and sensing with hundreds of ions and provide a promising route toward scaling up trapped ion quantum platforms because of the ability to trap and control up to thousands of ions in 2D and 3D crystals. A leading source of decoherence in laser-based multiqubit operations on trapped ions is off-resonant spontaneous emission. While many trapped ion quantum computers or simulators utilize clock qubits, other systems rely on Zeeman qubits, which require a more complex calculation of this decoherence. We examine theoretically the impacts of spontaneous emission on quantum gates performed with trapped ions in a high magnetic field. We consider two types of gates -- light-shift and Molmer-Sorensen gates -- and compare the decoherence errors in each. We also compare different detunings, polarizations, and required intensities of the laser beams used to drive the gates. We show that both gates can have similar performance at their optimal operating conditions and examine the experimental feasibility of various operating points. By examining the magnetic field dependence of each gate, we demonstrate that when the $P$ state fine structure splitting is large compared to the Zeeman splittings, the theoretical performance of the Molmer-Sorensen gate is significantly better than that of the light-shift gate. Additionally, for the light-shift gate, we make an approximate comparison between the fidelities that can be achieved at high fields with the fidelities of state-of-the-art two-qubit trapped ion quantum gates. We show that, with regard to spontaneous emission, the achievable infidelity of our current configuration is about an order of magnitude larger than that of the best low-field gates, but we also discuss alternative configurations with potential error rates that are comparable with state-of-the-art trapped ion gates.