CASE STUDY qubits to perform complex operations – necessitating impractical amounts of infrastructure and control electronics. This renders them unlikely to be able to be implemented beyond small-scale experiments and devices.
A practical, large-scale, fault-tolerant quantum computer requires an architecture that is:
• Fault-tolerant to suppress enough errors for useful algorithms to succeed.
• Able to prepare and measure logical qubits through computation.
• Capable of applying universal instructions to these logical qubits.
• Able to decode measurements from logical qubits in real-time and can alter subsequent instructions.
• Modular to scale to hundreds or thousands of logical qubits to run more complex algorithms.
• Efficient enough to execute meaningful algorithms with realistic physical resources, such as energy and infrastructure.
IBM is introducing two new technical papers that detail how it will solve the above criteria to build a large-scale, fault-tolerant architecture.
The first paper unveils how such a system will process instructions and run operations effectively with qLDPC codes. The second paper describes how to efficiently decode the information from the physical qubits and charts a path to identify and correct errors in real-time with conventional computing resources.
From roadmap to reality
The new IBM Quantum Roadmap outlines the key technology milestones that will demonstrate and execute the criteria for fault tolerance. Each new processor in the roadmap addresses specific
IBM Quantum Starling – summary
• IBM Quantum roadmap, processors, and infrastructure outline clear path to IBM Quantum Starling, expected to be first largescale, fault-tolerant quantum computer
• Breakthrough research defines key elements for an efficient fault-tolerant architecture – charting the first viable path toward a system projected to run 20,000 times more operations than today’ s quantum computers
• Representing the computational state of IBM Starling would require the memory of more than a quindecillion( 1048) of the world’ s most powerful supercomputers
challenges to build quantum computers that are modular, scalable, and error-corrected:
• IBM Quantum Loon, expected in 2025, is designed to test architecture components for the qLDPC code, including " C-couplers " that connect qubits over longer distances within the same chip.
• IBM Quantum Kookaburra, expected in 2026, will be IBM ' s first modular processor designed to store and process encoded information. It will combine quantum memory with logic operations – the basic building block for scaling fault-tolerant systems beyond a single chip.
• IBM Quantum Cockatoo, expected in 2027, will entangle two Kookaburra modules using " L-couplers." This architecture will link quantum chips together like nodes in a larger system, avoiding the need to build impractically large chips.
Together, these advancements are being designed to culminate in Starling in 2029. p
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