Quantinuum and the University of Colorado Boulder have advanced quantum error correction by implementing a high-rate non-local quantum Low Density Parity Check (qLDPC) [[25,4,3]] code on the H2 quantum processor. The [[25,4,3]] notation refers to the use of 25 physical qubits to encode 4 logical qubits with a distance between codewords of 3. The four error-protected logical qubits were entangled in a GHZ state and achieved better fidelity than if physical qubits were used without the error correction. This achievement marks the first time anyone has entangled four logical qubits with superior fidelity to their physical counterparts.

The team, including members without specialized knowledge of quantum hardware, leveraged Quantinuum’s hardware and software stack to reach this milestone. This capability allows quantum programmers to run advanced programs on commercial machines, significantly enhancing accessibility and reliability. The results align with Quantinuum’s recent partnership with Microsoft, where they demonstrated logical fidelities exceeding physical fidelities on entangled bell pairs and completed multiple rounds of error correction.

The implemented qLDPC code offers a very high encoding rate, enabling a proportional increase in logical qubits relative to physical qubits. This advancement promises more efficient scaling of quantum machines compared to traditional codes with limited logical qubit capacity. Quantinuum’s progress in quantum fault tolerance positions it ahead of competitors in the race for scalable quantum computing.

For additional information, you can access a news release Quantinuum has provided here and you can read the scientific preprint paper posted on arXiv here.

July 3, 2024