IBM reports 99% average quantum state transfer between two processors

IBM researchers report connecting two Nighthawk R1 quantum processors with four links that transferred quantum states with 99% average fidelity. Each link used an 80-centimeter cable inside a dilution refrigerator, demonstrating multiple connections between full processor chips. The team also used the links to perform operations between qubits on separate processors, achieving 94.75% average two-qubit gate fidelity across the four links. Two links operated simultaneously to create independent entangled states. The experiment connected only a subset of the processors' qubits for development. IBM says further work includes improving link yield, reproducibility and error rates before integrating more connections into larger systems.