Inexpensive Quadrupole Traps for Teaching Undergraduates

Trapped ions are a promising candidate for qubits with demonstrated low error rates and options for scalable architectures. With the growth of quantum information science in academia and industry, there is a need for inexpensive, scalable educational labs to introduce students to concepts in quantum computing. To fill this need, we developed a reproducible lab for physics and engineering students. The lab demonstrates key concepts in ion trapping. The lab consists of two, independent quadrupole traps: a four-rod trap and a planar five-rail trap. To reduce cost and complexity, we trap charged particles with 25 μm and 50 μm diameter. The particles are trapped in air, at atmospheric pressure. Due to the damping forces provided by this background gas, the trapped particles are easy to control. We demonstrate several possible experiments with these traps, including controlling the number of particles trapped through voltage modulation at a constant frequency, studying the phase transition between one- and two-dimensional Coulomb crystals, exploring micromotion compensation, observing two- and three-particle secular modes, and demonstrating particle shuttling along the trapping axis of the planar trap.