Abstract
Suppressing errors is the central challenge for useful quantum computing(1), requiring quantum error correction (QEC)(2-6) for large-scale processing. However, the overhead in the realization of error-corrected 'logical' qubits, in which information is encoded across many physical qubits for redundancy(2-4), poses substantial challenges to large-scale logical quantum computing. Here we report the realization of a programmable quantum processor based on encoded logical qubits operating with up to 280 physical qubits. Using logical-level control and a zoned architecture in reconfigurable neutral-atom arrays(7), our system combines high two-qubit gate fidelities(8), arbitrary connectivity(7,9), as well as fully programmable single-qubit rotations and mid-circuit readout(10-15). Operating this logical processor with various types of encoding, we demonstrate improvement of a two-qubit logic gate by scaling surface-code(6) distance from d = 3 to d = 7, preparation of colour-code qubits with break-even fidelities(5), fault-tolerant creation of logical Greenberger-Horne-Zeilinger (GHZ) states and feedforward entanglement teleportation, as well as operation of 40 colour-code qubits. Finally, using 3D [[8,3,2]] code blocks(16,17), we realize computationally complex sampling circuits(18) with up to 48 logical qubits entangled with hypercube connectivity(19) with 228 logical two-qubit gates and 48 logical CCZ gates(20). We find that this logical encoding substantially improves algorithmic performance with error detection, outperforming physical-qubit fidelities at both cross-entropy benchmarking and quantum simulations of fast scrambling(21,22). These results herald the advent of early error-corrected quantum computation and chart a path towards large-scale logical processors.