A way to address the individual ions of a rotating ion crystal could allow scientists to perform quantum simulations in which each qubit can be carefully controlled.
We implement individual addressing and readout of ions in a rigidly rotating planar crystal in a compact, permanent magnet Penning trap. The crystal of ^{40}Ca^{+} is trapped and stabilized without defects via a rotating triangular potential. The trapped ion fluorescence is detected in the rotating frame for parallel readout. The qubit is encoded in the metastable D_{5/2} manifold enabling the use of high-power near-infrared laser systems for qubit operations. Addressed σ_{z} operations are realized with a focused ac Stark shifting laser beam. We demonstrate addressing of ions near the center of the crystal and at large radii. Simulations show that the current addressing operation fidelity is limited to ∼97% by the ion's thermal extent for the in-plane modes near the Doppler limit, but this could be improved to infidelities <10^{-3} with sub-Doppler cooling. The techniques demonstrated in this Letter complete the set of operations for quantum simulation with the platform.
Abstract Using a 2D ion crystal for quantum simulation and computation has been pursued for a long time. The coherent manipulation of a stationary 2D crystal in the Paul trap may be hampered by the micromotion synchronous with the oscillating electric field. Here, a simple Paul trap that stably confines over 20 ions in a stationary 2D crystal is presented. The disturbance of the micromotion in coherent operations is mitigated by making the direction of micromotion perpendicular to the transverse direction of the 2D crystal. To achieve the condition of perpendicularity, the structure of the trap electrodes is comprehensively designed, which also provides the controllability of rotating principal axes. The transverse vibrational modes by Raman laser‐beams are addressed and coherent evolution of sideband transitions on these modes observed. Moreover, this trap allows for optical access with a 0.86 numerical aperture which facilitates applying individually addressing laser‐beams. This work can be an example of realizing a 2D‐trapped‐ion based quantum simulator and computer in a Paul trap.
Trapped ions boast long coherence times and excellent gate fidelities, making them a useful platform for quantum information processing. Scaling to larger numbers of ion qubits in RF Paul traps demands great effort. Another technique for trapping ions is via a Penning trap where a 2D crystal of hundreds of ions is formed by controlling the rotation of the ions in the presence of a strong magnetic field. However, the rotation of the ion crystal makes single ion addressability a significant challenge. We propose a protocol that takes advantage of a deformable mirror to introduce AC Stark shift patterns that are static in the rotating frame of the crystal. Through numerical simulations we validate the potential of this protocol to perform high-fidelity single-ion gates in crystalline arrays of hundreds of ions.
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.