Characterizations of long-range Rydberg interactions of ¹⁷¹Yb for large-scale high-fidelity two-qubit quantum gates

High-fidelity two-qubit quantum gates mediated by the Rydberg blockade scheme in optical tweezer arrays have seen remarkable advancements recently. In particular, we have demonstrated 99.72(3) % two-qubit gate fidelity after excluding the atomic loss with ¹⁷¹Yb atom array^1. Here, the Rydberg states’ strong interactions between a closely arranged atom pair play a key role in realizing the conditional Controlled-Z (CZ) two-qubit gate. In order to further improve the gate fidelity, a full understanding of the properties of the Rydberg states and interactions between Rydberg atoms is necessary, apart from contributions of other operation error sources. In this work, we design a novel quantum circuit to precisely measure the long-range Rydberg interaction strength between ytterbium atoms under our current magnetic field. We also mapped out different angled atom pair interaction strengths relative to the magnetic field direction. The long-range interactions between nearest atom pairs for Rydberg-based CZ gates induce extra detuning errors and could be a limitation of fully utilizing the potential of the large-scale atom arrays. Our experimental data reasonably agreed with the theoretical calculations based on the multichannel quantum defect theory (MQDT). Lastly, we will report an updated measurement of two-qubit gate fidelity after reducing the laser noise participating in the gate operation. The improvement of the two-qubit gate fidelity is a key step to reach the error rate threshold for quantum error correction.