Microwave near-field control of 9Be+ qubits in a surface-electrode ion trap

We describe experiments employing microwave near-fields from conductors embedded in a surface-electrode ion trap. Our optimized trap geometry features a single conductor to induce all the required spin-motional couplings typically used in multi-qubit quantum operations. We load 9Be+ ions via two-photon ionization from an ablation plume created by single shots of a pulsed laser. Our experiment operates at 22.3\,mT where the |F=2,mF=1> and |F=1,mF=1> states form a first-order field-independent qubit for long coherence times. We demonstrate initialization and control of the qubit. We perform a spatial characterization of the microwave near-field employing a modified Ramsey / echo sequence with a single ion as a local field probe and find excellent agreement with numerical simulations of the fields. Using the spatial variation of the microwave near-field, we demonstrate motional sideband transitions on our field-independent qubit as a basic prerequisite in entangling multi-qubit quantum logic gates.