IBM goes big to keep quantum computers cold

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 incorporated three essential components from the environment used in IBM Quantum System Two while allowing engineers to test, improve and rapidly iterate on each component independently.

According to IBM, the approach could help the company speed up development of the cryogenic infrastructure needed for larger quantum systems.

The next stage will put quantum processors inside the new cooling system. IBM said it plans to install IBM Quantum Nighthawk processors in the cryogenic modules later this year to expand operational performance testing.

In the announcement, IBM’s roadmap called for L-couplers to connect multiple processors in a larger quantum computer with at least 1,000 programmable qubits by 2027. Qubits are the basic units of information in a quantum computer, and IBM defines programmable qubits as those that can be directly used to perform computations. By the time IBM delivers Starling in 2029, the company said each cryogenic module could house thousands of programmable qubits.

Cooling represents one part of a broader quantum computing effort. IBM introduced its plans for Starling last year alongside a new error-correction code that the company said dramatically reduced the physical resources required for fault tolerance. Since then, IBM said it has demonstrated core hardware components and made progress on more efficient error-correction decoding.

The work “will accelerate our progress alongside continued innovation in quantum hardware, software, and algorithms,” Gambetta said.