Individual addressing of a linear chain of ions using a crossed AOD system

Abstract

This project presents the development and characterization of a crossed acousto-optic deflector (AOD) system operating at 355 nm, aimed at enabling high-resolution beam steering for indi- vidual ion addressing in trapped-ion quantum computing. To meet the stringent spatial and temporal requirements of scalable quantum control, we experimentally evaluated the system’s beam waist stability, diffraction efficiency, angular deflection, and steering resolution over a radio frequency range of 130–210 MHz at two RF power levels: 37 dBm (5.0 W) and 40 dBm (10.0 W). Peak first-order diffraction efficiency reached 60.0±1.1% at 40 dBm, approaching the manufac- turer’s specification of 70%, with optimal performance observed near the center frequency of 170 MHz. The vertical AOD consistently outperformed the horizontal AOD in efficiency, and the combined diagonal diffraction efficiency peaked at 180 MHz. Beam deflection angles showed strong linearity with RF frequency, with measured sensitivities up to 0.0128 mrad/MHz and R2 >0.998, albeit deviating from the theoretical prediction of 0.0623 mrad/MHz. Despite the manufacturer’s claim of over 100 resolvable spots, practical resolution was limited to 4–5, constrained by suboptimal beam waist sizes (95–120 µm versus the ideal 2.5 mm) and thermal fluctuations in the laboratory environment. Beam waist stability was within ±4.5 µm across the tuning range, which is sufficient for proof-of-principle operation but may pose chal- lenges for tightly spaced ion chains. The observed limitations, including thermal drift in the Paladin laser, polarization mismatch, and suboptimal AOD mounting geometry, underscore the importance of improved thermal control and alignment precision. Nonetheless, the system demonstrated reliable frequency-to- position mapping and beam behavior consistent with vectorial beam steering theory, validating its potential for scalable quantum applications.