The trapping of individual ions has allowed physicists to control and observe otherwise inaccessible phenomena. Ion traps have enabled the most precise measurements of fundamental physical constants, mass spectrometry for chemical characterization, atomic clocks that would only lose a fraction of a second over the entire age of the universe, and the direct observation of many core concepts in quantum mechanics. Many crucial developments in ion traps occurred here at the University of Washington in the group of Hans Dehmelt, who shared the 1989 Nobel Prize in physics for that work. Today, techniques in ion trapping continue to be developed because trapped ions are one platform for creating qubits in quantum computers. 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, which demonstrates key concepts in ion trapping. Our process utilized, first, a comparative approach with reference to literature and, second, iterative improvement on built components. 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, rather than atomic ions. 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. The result of our project is a lab capable of several experiments, 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.

Trapped ions are one of the promising candidates for an operating quantum computer. Ions trapped in an electromagnetic trapp serve as a physical qubit, where the qubit states are manipulated by applying lasers to the system. As quantum computers use quantum gates with a given precise angle of rotation of the qubit state within the Bloch sphere, applying a laser with very narrow bandwidth is essential for minimizing errors, and thus stabilization of laser frequency is a required process for trapped ion qubit control. In our project, we stabilize the 1762 nm InfraRed fiber laser by using an optical cavity lock, where we obtain the resonant frequency of the cavity by measuring the intensity of the laser across the Fabry-Perot cavity, while varying the laser frequency. However, this model cannot distinguish between the laser intensity noise and the laser frequency noise. To address this, we eliminate the intensity noise by analyzing the signal reflected back from the cavity, where we observed a frequency dependent signal which reaches zero at resonance, allowing us to stabilize the laser to the desired frequency. A deeper understanding of the laser stabilization techniques may help us to minimize the trapped ion qubit control errors.