A scalable trapped-ion quantum computer demands efficient fluorescence collection from many readout zones distributed over a large chip area. We present a compact, monolithically integrated approach in which a metalens is fabricated on the backside of a surface-electrode ion trap to collect and collimate ion fluorescence. A 40 × 100 μm aperture formed in the trap’s ground electrode yields a simulated point-source solid-angle collection efficiency of 0.91% and a measured point-source detection efficiency of 0.58%. Expanding the aperture to 40 × 600 μm increases the simulated collection efficiency to 3.17%, comparable to a conventional objective with a numerical aperture of 0.35. An engineered undercut beneath the electrodes surrounding the aperture preserves the collection efficiency while increasing the ion-to-dielectric separation. By directly collimating fluorescence at the trap, the metalens eliminates the need for high numerical aperture objectives. Arrays of such readout zones enable scalable, high-fidelity parallel state detection in large-scale trapped-ion quantum computers.
Lim et al. (Thu,) studied this question.