  Trapped, laser-cooled ions produce intense fluorescence. Detecting this
fluorescence enables efficient measurement of quantum state of qubits based on
trapped atoms. It is desirable to collect a large fraction of the photons to
make the detection faster and more reliable. Additionally, efficient
fluorescence collection can improve speed and fidelity of remote ion
entanglement and quantum gates. Here we show a novel ion trap design that
incorporates metallic spherical mirror as the integral part of the trap itself,
being its RF electrode. The mirror geometry enables up to 35% solid angle
collection of trapped ion fluorescence; we measure a 25% effective solid angle,
likely limited by imperfections of the mirror surface. We also study properties
of the images of single ions formed by the mirror and apply aberration
correction. Owing to the simplicity of its design, this trap structure can be
adapted for micro-fabrication and integration into more complex trap
architectures.
