University of Sydney Demonstrates Multi-Qubit Logical Entanglement and 170-Round Stability on IBM Square-Lattice Nighthawk r2 Processor – Quantum Computing Report

Researchers from the University of Sydney have demonstrated multi-qubit fault-tolerant logic and sustained error suppression on IBM Quantum‘s cloud-deployed ibm_phoenix processor, a 120-qubit superconducting system based on the square-lattice Nighthawk r2 architecture. The experimental findings, reported in an arXiv preprint (arXiv:2610.32347) and highlighted by IBM Research, validate distance-3 and distance-5 rotated surface code memories, logical Bell-state preparation via lattice surgery, and state and gate teleportation across three logical qubits. The results mark the first major multi-qubit logical benchmark executed on the platform just 54 days following its fleet integration.

Dynamic Role Alternation and Multi-Round Stability Benchmarks

A primary bottleneck in multi-round superconducting quantum error correction (QEC) is population leakage into non-computational states (such as the |2⟩ transmon state). While ancilla qubits are reset…