IBM L-Coupler Chip-to-Chip Quantum Link (two 120-qubit Nighthawk R1 chips, 99% state-transfer fidelity)

Track; not yet

Why

The preprint reports a real, reproducible-in-lab advance: four 80 cm aluminum links between two full 120-qubit Nighthawk R1 chips with 99.00% mean state transfer, three thermal cycles survived and 6-qubit GHZ entanglement across chips. But the useful operation, a distant CZ gate, is 94.75% on average, the entangled-state numbers reach about 91% only after readout-error mitigation, the cables are sensitive to magnetic fields, and the result is a single non-peer-reviewed prototype. IBM's 2027 (1,000+ qubit linked processors) and 2029 (Starling) targets are plans, not demonstrations. This is a meaningful modular-scaling milestone to watch, not something a buyer can act on.

Next

Watch for peer-reviewed publication or independent replication, distant CZ fidelity above 99% with improved L-qubit coherence (IBM targets about 100 microseconds), remated or reworked bond demonstrations, and the Nighthawk system-level tests in the modular cryogenic cells planned for late 2026.