Fault-Tolerant Operation and Materials Science with Logical Qubits on a Neutral-Atom Quantum Computer with Individual Optical Addressing and Non-destructive Readout*

Neutral atoms have emerged as a strong candidate architecture for scalable, fault-tolerant quantum computing. A popular approach for neutral atom gates involves shuttling atoms to and from a shared interaction zone. While atom shuttling enables parallel execution of multiple gates, local qubit addressing comes with distinct advantages, such as faster overall execution speed and the ability to perform non-identical gates in parallel. We present a full-stack universal quantum computing architecture featuring individual optical addressing of single atoms for fast gate execution without atom shuttling. Despite engineering challenges associated with individual addressing, we demonstrate gate fidelities as high as 99.35(4)% for controlled-Z (CZ) and 99.902(8)% for local Z-rotation gates. We also utilize our improved non-destructive state-selective readout to enable repeated re-use of atomic qubits and disambiguation of atom loss from other error mechanisms. With removal of atom-loss in the data, the CZ gate fidelity improves to 99.73(3)%. This individual optical addressing capability adds an important tool to the neutral-atom quantum computing platform to reduce circuit execution times to practical levels.

Furthermore, we demonstrate reduction in quantum computation error by encoding physical qubits into logical qubits using the [[4,2,2]] code (C4) and comparing the performance of different quantum circuits run through our software and hardware stacks. We show that logical performance surpasses physical performance for multiple circuits including Bell states (12x error reduction), random circuits (15x), and a prototype Anderson Impurity Model ground state solver for materials science applications (up to 6x, non-fault-tolerantly). In light of recent advances on applying concatenated C4/C6 codes to achieve error correction with high code rates and thresholds, our work can be regarded as a building block towards fault tolerant quantum computation.