IBM’s new modular architecture for cryogenic systems

To realize the full potential of quantum computing, we need to scale to much larger quantum systems than we have today. However, doing so requires more than just building bigger processors with more qubits. IBM’s superconducting quantum computers can only operate at temperatures colder than outer space, and they need highly specialized cooling systems to do so. For long-term scaling, refrigeration hardware has to evolve, too—and not only in terms of size.

The quantum computers of the future will depend on many processors reliably working on the same problems in tandem. Housing those processors will require larger cooling systems that can connect and work together. To address this challenge, IBM has announced a new modular architecture for cryogenic systems. By connecting processors through both quantum and classical links, information can move between chips to extend computations beyond the limitations of a single processor and enable more sophisticated quantum algorithms.

The new cryogenic architecture is a foundational component of IBM’s path toward realizing IBM Quantum Starling—the first fault-tolerant quantum computer—which is expected in 2029. We’ve already successfully demonstrated this new architecture with two coupled cryogenic cells. This demonstration provides early validation of the modular approach needed to realize our fault-tolerant quantum computers.

To get the learning, tools, and access you need to work with increasingly capable quantum systems, visit IBM Quantum Platform.

How does IBM’s modular cryogenic architecture build on existing solutions?

Today’s superconducting quantum computers are typically housed in isolated cylindrical cryostats: vacuum-insulated containers in which dilution refrigerators cool processors to temperatures near absolute zero. By maintaining dilution refrigerators’ extremely low temperatures for long periods of time, cryostats minimize sources of potential disruption such as excess heat and thermal noise, allowing quantum states to last long enough for reliable computation.

IBM Quantum System One, IBM’s first quantum computer available outside the lab, is housed in a traditional cylindrical cryostat.

This approach has enabled the quantum computers we use today, from IBM’s first cloud-accessible quantum computer in 2016, which had just five qubits, to the 1000+ qubit IBM Quantum Condor unveiled in 2023. However, this journey has also revealed the limitations of single-chip scaling, which poses enormous challenges due to spatial constraints, excessive heat generation, and qubit crosstalk.Qubit crosstalk refers to unwanted interference in quantum computers caused by operations meant for a specific qubit unintentionally affecting adjacent qubits, resulting in noise and calculation errors.

Researchers have discovered promising strategies for overcoming these limitations by distributing computational workloads across multiple connected processors, which either solve small subproblems separately and combine the results, or operate together as a more powerful unified system. These innovations have led IBM to two conclusions:

1. Modularity is key to the long-term scaling of quantum processors.
2. Traditional self-contained cryostats won’t be suitable for the connected quantum systems of the future.

IBM’s new modular cryostats use established dilution refrigerator technology to cool quantum processors, but they go beyond their predecessors by taking the form of box-shaped cryogenic “cells.” Made of solid aluminum panels and framing, each cell—a complete cryogenic environment—can house a quantum processor and reliably connect to adjacent cells. Where cylindrical cryostats require long and noisy connections between processors, the modular box format allows cells to sit tightly side-by-side with short interconnect paths.

The interior of a modular cryostat. The golden “chandelier” is a multi-tiered dilution refrigerator that cools a quantum processor held on the bottom tier.

By allowing quantum information to move between processors with reduced overhead, and by providing more room for other cryogenic electronics, this architecture paves the way for the scalable, connected quantum systems that will serve as a foundation for fault-tolerant computers.

What makes modular cryogenic architecture easier to maintain, upgrade, and scale?

With the new modular approach, each cryogenic cell is fitted with its own vacuum chamber, cooling hardware, and thermal shielding. When two or more cells are connected, quantum cables are routed through one cell’s opening into an adjacent cell, and multiple layers of thermal shielding are connected to form a protected cryogenic tunnel between systems. This tunnel connects the processors while maintaining the low temperatures required of quantum systems.

The advantages of this architecture also extend beyond connectivity. Even when linked together, the design of the shield layers keeps the thermal interaction between adjacent cells to a minimum. As more cells are connected, cool down times and temperature stability remain consistent, allowing for a highly scalable system without disruptions to computational performance.

Two connected modular cryostat prototypes operating in Poughkeepsie, NY.

Additionally, this modularity makes future upgrades on a cell-by-cell basis significantly easier to implement. Larger than any previous cryogenic solution and roughly 3x the size of a typical kitchen fridge, each cell provides approximately 0.53 square meters of available wiring area and 2.75 cubic meters of vacuum chamber volume. Its size supports the deployment of larger single processors and denser system configurations, setting the stage for future generations of quantum hardware without requiring redesigns of the entire cryogenic system.

Why isn’t IBM using existing modular approaches for cryogenics?

Unlike general-purpose modular cryogenic solutions, IBM’s modular approach is designed specifically for IBM quantum computers. The architecture is built to align with IBM’s long-term goals for connected multi-chip quantum systems, with every aspect tailored to advancing readout wiring, processor designs, and cryoelectronics.

A look inside IBM's new modular cryogenic architecture.

IBM has already demonstrated this architecture in practice in our quantum facility in Poughkeepsie, NY, where two modular cryogenic cell prototypes were successfully coupled and operated together.

Designed for long-term expansion and IBM-specific hardware, this modular approach circumvents the need to redesign the entire cryogenic infrastructure as systems grow, enabling the next-generation quantum systems.

How do modular cryostats fit into the IBM Quantum Roadmap?

With future versions of single cells expected to be capable of supporting at least 2,000 qubits each—a higher qubit count than IBM fabricates on any single chip today—the new modular cryostat architecture introduces the infrastructure needed to support larger quantum systems on the path to fault-tolerant quantum computing.

Importantly, this architecture will be available for our researchers to explore before the arrival of IBM Quantum Starling, allowing us to validate key capabilities in quantum hardware. Researchers could also use these cryostats to test essential components in IBM’s modular fault-tolerant architecture such as l-couplers, long-range quantum interconnects first demonstrated in 2024.Developed to enable long-range connections between quantum chips, l-couplers are cables that can operate inside dilution refrigerators and connect QPUs on the one meter scale.

By providing a foundation for future generations of quantum hardware without requiring major redesigns of the underlying cryogenic infrastructure, modular cryostats build a bridge between today’s single-chip deployments and the larger, interconnected systems on the IBM Quantum Roadmap.

As IBM’s hardware advances, we’re also expanding the software and developer capabilities needed to experience the full potential of our quantum systems. Visit IBM Quantum Platform to explore them today.