Comparing optimized pulsed sideband cooling and continuous sideband cooling for optical qubits*

Trapped-ion quantum computers rely on two-qubit gates that achieve optimal performance when the ions are near the ground state of motion. Ion cooling, however, takes up a significant amount of the time required to prepare the qubit register, and as the computer scales, cooling the ions in the middle of the algorithm becomes more critical. Therefore, cooling can be a significant source of latency in the algorithm. Recently, a graph theoretic method of determining the optimal set of sideband cooling (SBC) pulses for a given trapped ion system has been proposed and experimentally demonstrated [1]. Here, we investigate the difference in efficiency of optimized pulsed SBC versus continuous SBC [2] for optical qubits using numerical simulation and experimental confirmation with ⁴⁰Ca⁺ ions. 

[1] A. J. Rasmusson, M. D'Onofrio, Y. Xie, J. Cui, & P. Richerme. Optimized pulsed sideband cooling and enhanced thermometry of trapped ions. Phys. Rev. A 104, 043108 (2021).

[2] F. Diedrich, J. C. Bergquist, W. M. Itano, & D. J. Wineland. Laser Cooling to the Zero-Point Energy of Motion. Phys. Rev. Lett. 62, 403 (1989).