IQM Quantum Computers has developed a novel quantum error-correcting code that achieves up to three orders of magnitude lower logical error rates than the surface code, while requiring up to eight times fewer physical qubits. The breakthrough, termed barbell codes, addresses the critical challenge of quantum error correction by significantly reducing hardware complexity without performance trade-offs. This advancement positions the company on a credible path toward scalable fault-tolerant quantum computing.

Barbell codes and hardware efficiency

Unlike many alternative high-performance approaches, barbell codes maintain a comparatively low hardware complexity. The technology is a family of quantum low-density parity-check (QLDPC) codes tailored to IQM's Constellation, a quantum processor topology with enhanced planar connectivity. In this topology, each qubit can natively interact with 12 other qubits, compared to four in a conventional square grid. The design requires only three couplers for computational qubits and six for central elements.

By exploiting qubit connectivity and requiring only a single long coupler connection for every other qubit, barbell codes enable high-performance error correction with dramatically reduced hardware complexity. The unique design eliminates the need for additional long-range crossing couplers on open boundary conditions, simplifying fabrication without compromising performance.

Performance and deployment roadmap

The development details and numerical performance analysis published by the IQM team on arXiv demonstrate a major advancement in quantum computing. Barbell codes are constructed by connecting two sites of standard planar Constellation connectivity with a single long coupler for every second qubit, providing the capability for generating entanglement between such pairs. The result is a solution engineered for the practical realities of superconducting qubit manufacturing rather than ideal laboratory conditions.

"We are pioneering the next chapter in quantum computing," said Jan Goetz, CEO and Co-founder of IQM Quantum Computers. "Our approach offers a highly competitive path to scalable quantum error correction with superconducting qubits, paving the way for large-scale, fault-tolerant quantum computers."

Strategic milestones

IQM has sold more quantum systems than any other manufacturer and will deploy 150-qubit systems to customers later this year. The company has further announced IQM Halocene, an advanced quantum computer for error correction codes. The barbell codes approach aligns with the company's development roadmap, positioning IQM on a path to fault-tolerant quantum systems with hundreds of high-precision logical qubits and the possibility of quantum advantage across multiple industries.

Recently, IQM announced increased commitments to its Private Investment in Public Equity (PIPE), driven by upsized investor demand. This move precedes its planned Nasdaq listing through a merger with Real Asset Acquisition Corp. (NASDAQ: RAAQ). Founded in 2018 and headquartered in Finland with major operations in Munich, IQM has over 400 employees and operates across Europe, Asia, and North America.