Making Trapped-Ion Entangling Gates Robust to Optical Crosstalk through Spectator Coupling Minimization

We explore the ability to minimize the impact of optical crosstalk when performing a Mølmer-Sørensen (MS) style entangling gate in a trapped ion system through the use of spectator coupling minimization. Optical crosstalk during a MS style entangling gate causes unwanted entanglement between the target ions and the spectator ions affected by crosstalk, presenting a barrier to running high-fidelity entanglement gates. Using spectator coupling minimization, and building upon previous work using discretized pulses, we demonstrate the ability to decrease the infidelity caused by unwanted optical crosstalk between target and spectator ions through intelligent mode choice allowing for high-fidelity fast entangling gates with realistic laser properties. Using Sandia's QSCOUT trapped ion quantum computer, the efficacy of this method was demonstrated at varying levels of crosstalk.