IBM connected two large, ultracold cryogenic modules, clearing an engineering hurdle on the way to a much larger quantum computer. The new system tackles a practical problem facing efforts to scale quantum computing: how to keep growing numbers of quantum processors cold enough to operate while giving engineers enough space to connect them. IBM said its modular architecture could eventually link hundreds of quantum chips and support its plan to build IBM Quantum Starling, the world’s first fault-tolerant quantum computer, targeted for 2029. Fault tolerance aims to let a quantum computer continue operating reliably despite errors by detecting and correcting them. IBM said Starling would combine advances in error correction, processor design, decoding and systems engineering. “The successful connection and operation of these cryogenic modules signals a leap forward in that direction,” Jay Gambetta, Director of IBM Research and IBM Fellow, said in IBM’s announcement. Superconducting quantum processors operate at ultracold temperatures. IBM said its first two connected cryogenic modules jointly reached 4 Kelvin, roughly the temperature of liquid helium, in less than five days, then cooled to below 15 millikelvin. IBM said the larger enclosure also created more room for wiring. Each module’s vacuum enclosure offered up to 12 times more wiring space than the enclosures in its most widely used IBM quantum systems, according to the company. The additional space enabled more chip-to-chip connections within individual modules and between separate modules. The company designed the box-shaped modules to connect in a tight row. This layout created room to link separate quantum processors directly through IBM’s L-coupler technology. IBM said L-couplers allow separate quantum chips to share information, communicate and operate as parts of a larger quantum computer. This modular architecture also gives IBM a way to work on parts of the cryogenic system separately. IBM said the design