IBM announced a new modular architecture for cryogenic systems used in its superconducting quantum computers, in a move aimed at overcoming the scaling limitations of single-chip quantum processors. The design is based on separate cooling cells that can be connected side by side, allowing information to pass between multiple processors through quantum and conventional links, rather than confining operations to a single processor.
IBM’s superconducting quantum computers operate at temperatures lower than outer space, requiring dilution refrigerators and specialized thermal barriers to keep quantum states stable for long enough to perform computations. The company believes that increasing the number of qubits requires not only larger processors, but also a cooling architecture capable of accommodating and connecting multiple processors while maintaining thermal stability.
From Cylindrical Structures to Connectable Cells
Current quantum systems are typically placed inside vacuum-insulated cylindrical vessels. This approach enabled IBM to progress from its first quantum computer available through the cloud in 2016, which had five qubits, to the IBM Quantum Condor processor, which it unveiled in 2023 with more than 1,000 qubits. However, scaling on a single chip faces limitations related to space, heat generation, and unwanted interference between qubits.
Instead, the new cells have a box-like shape and are made from aluminum panels and structures. Each cell contains a complete cooling environment, with its own vacuum chamber, cooling equipment, and thermal barriers, while dedicated openings allow quantum cables to pass to neighboring cells. Placing the cells directly next to one another helps shorten connection paths compared with the long links between cylindrical vessels.
What Changes in Practice?
The thermal-protection layers are designed to limit thermal interaction between adjacent cells. According to IBM, cooling times and temperature stability are expected to remain similar as new cells are added, enabling the system to be expanded without disrupting computational performance. The system can also be upgraded one cell at a time, rather than requiring the entire cooling architecture to be redesigned when new processors or quantum electronics are introduced.
Each cell has approximately 0.53 square meters of available wiring space, and its vacuum chamber has a volume of 2.75 cubic meters, while the cell’s overall volume is approximately three times that of a typical kitchen refrigerator. This space provides room for larger processors and denser configurations, as well as accommodating a greater number of connections and electronics within the cold environment.
A Step Toward Fault-Tolerant Quantum Systems
IBM tested the new architecture in practice by operating two connected cooling cells at its facility in Poughkeepsie, New York. The company considers the experiment an initial validation of the approach required to build multi-chip quantum systems capable of distributing tasks across connected processors or operating them as a more powerful unified system.
IBM places this architecture on its path toward IBM Quantum Starling, which it describes as the first fault-tolerant quantum computer and expects in 2029. It also expects future versions of the single cell to support at least 2,000 qubits. The systems will allow researchers to test components of IBM’s modular quantum architecture, including l-couplers, first demonstrated in 2024 for connecting quantum processing units over a distance of up to one meter.