Southwest Quantum Information and Technology

Automation of magneto-optical trap laser tuning for neutral atom quantum computing

Presenting Author: Andrew Jarymowycz, California Polytechnic State University
Contributing Author(s): Michael Pilgrim, Jonathan Flores, Katharina Gillen

Neutral atom quantum computers use atoms trapped by light as qubits. Our group computationally explores light patterns useful for quantum computing [1-3] and investigates their properties experimentally. To hold atoms in light patterns, they must first be cooled to sub-mK temperatures by a magneto-optical trap (MOT) using lasers and magnetic fields. The MOT requires two lasers (trap and repump) tuned to the correct atomic transitions to within 1:100,000,000. We developed Python code to automate the time-consuming process of tuning our diode lasers. Tuning steps are: Atomic vapor, with atoms moving in all directions at room temperature speeds, has a spectrum broadened by the Doppler effect. Thus, we first make the detailed, hyperfine energy levels of our 87Rb atoms visible using saturated absorption. Next, to identify the correct energy level transitions for each laser, we calculate the conversion factor between the applied tuning voltage and the resulting laser frequency by comparing the narrow peaks of a 300 MHz free spectral range Fabry-Perot interferometer to the saturated absorption spectrum. Lastly, the optoelectronic feedback signal is adjusted to place zero feedback voltage at the correct laser frequency. The only remaining manual step is flipping the lock switch to close the feedback loop. Now the cold atom sample is ready to be loaded into the light patterns for quantum computing. [1] PRA 73, 013409 (2006), [2] PRA 82, 063420 (2010), [3] PRA 83, 023408 (2011).

(Session 5 : Thursday from 12:00pm-2:00 pm)