IQM’s QLDPC Codes Need 8× Fewer Qubits Than Surface Code

IQM Quantum Computers has unveiled a new family of quantum low-density parity-check (QLDPC) codes, dubbed barbell codes, that require up to eight times fewer physical qubits than the widely used surface code for quantum error correction. This advancement addresses a critical hurdle in building practical quantum computers by simultaneously reducing hardware demands and achieving three orders of magnitude lower logical error rates. The codes are specifically designed for IQM’s Constellation processor, where each qubit can natively interact with 12 others, an improvement over the four qubits possible in conventional designs. Jan Goetz, CEO and Co-founder of IQM Quantum Computers, said that their approach offers a competitive path to scalable quantum error correction with superconducting qubits, enabling large-scale, fault-tolerant quantum computers.

Barbell Codes Achieve Lower Error Rates with Fewer Qubits

The team’s findings, published on arXiv, detail how these codes are specifically tailored to IQM’s Constellation processor topology, which offers enhanced connectivity compared to conventional square grid designs. By strategically connecting sites of standard planar connectivity with a single long coupler for every second qubit, the codes generate entanglement while minimizing the need for complex fabrication processes. This design eliminates the need for additional long-range couplers on open boundary conditions, simplifying manufacturing without sacrificing performance, a critical consideration for real-world implementation.

According to details published on arXiv, the IQM team engineered this solution for the practical limitations of superconducting qubit manufacturing, rather than relying on idealized laboratory conditions. The result is a system that balances high performance with reduced hardware demands, a crucial consideration for scaling quantum computers beyond current limitations.