SqaleSim: Towards realistic noisy simulations of neutral atom quantum computers

Efficient and accurate quantum circuit simulation under realistic noise conditions is essential for the development and validation of fault-tolerant quantum computing. Our simulator, SqaleSim, models each atom as a five-level system comprising the computational qubit subspace {∣0⟩,∣1⟩}\{|0⟩, |1⟩\}{∣0⟩,∣1⟩}, two leakage states, and a loss state. It extends a Clifford-only simulator to efficiently handle small non-Clifford rotation and leakage outside the qubit subspace. Non-Clifford operations are approximated using Pauli Twirling, while transitions to non-computational states are tracked semi-classically. Additionally, the simulator incorporates atom motion, modeling phase errors induced during transport. This enhanced framework enables scalable and modality-specific error modeling, advancing the fidelity of quantum circuit simulations.