A massive leap in quantum computing: Microsoft and Quantinuum achieve 800x fault-tolerance with logical qubits as Microsoft and Quantinuum have together achieved a high success rate of computations on Microsoft’s quantum qubit virtualisation system combined with Quantinuum’s ion-trap hardware with minimal errors which is 800x better than physical qubits. This was achieved after 14,000 individual experiments were run without any error.

In quantum computing, decoherence which is the existence of noise, is a major part of physical qubits. This noise affects the results of computations as it contributes to high-error returns that are seen in quantum computers today. So, to make qubits useful, noise must be reduced drastically or technically totally eliminated. If this is done, the application of quantum computing will become widely acceptable since the data will be preserved, and results will be error-free at all times and in all instances.

What Microsoft has done is that physical qubits can be combined with its virtualisation system to create logical qubits that can perform error correction quickly without destroying the qubits and this is exactly what was achieved when Quantinuum’s System Model H2 quantum computer combined with Microsoft’s system to achieve logical qubits that are useful and reliant.

This has ushered in a new level of development in the quantum computing ecosystem. Fault-tolerant (a situation where a computer is able to compute correct results even when there is an error or fault in the process) quantum computers were thought to be achieved sometime in the future due to the unavailability of physical qubits that can reduce error rates. However, this has proven that large-scale fault-tolerant quantum computers are now in existence based on this recent feat. 

Quantinuum reports that this would not have been if there was no collaboration among players. A collaboration journey with Microsoft Azure Quantum that has taken over five years undergoing processes of error correction and diagnostics, optimisation of the virtualisation system, and the creation of logical qubits with only 30 physical qubits despite the estimates of at least 300 physical qubits has yielded massive results. This is the power of collaboration for engineering excellence.

Error corrections are not possible if the underlying physical qubits do not have high fidelity. High-fidelity qubits are the foundation upon which quantum computing can scale. If the qubits have low fidelity, then carrying out error correction will add more noise to the qubits. However, if the physical qubits have good enough qubits, then, error corrections tend to reduce the noise in the qubits thereby achieving logical qubits. 

This is the principle that Microsoft has applied to achieve fault-tolerance in their logical qubits moving it away from the current noisy intermediate-scale quantum (NISQ) level to Level 2 Resilient quantum computing. The approach entails entangling clusters of physical qubits to form a logical qubit, storing pertinent quantum data within this entangled state, and executing computations with error correction through intricate functions. The objective is to achieve logical qubit errors that are lower than those at the physical level.

The future of quantum computing is looking great seeing the massive progress that is happening in the space. Quantinuum plans to introduce a new series of quantum computers in 2025. The H-series quantum computer, Helios, will improve both physical fidelity and physical qubit count. This will enable a lower threshold for errors which will further support at least 10 highly reliable logical qubits. This move brings the entire industry closer to the commercialization of quantum computers and their applications across industries.