The road to fault-tolerant quantum computing

Even current classical computers can sometimes produce errors. But their error rates are somewhere in the range of $10^{-18}$. This means, only one in every trillion operations is faulty. In classical computing, error correction techniques (such as copying the bits we work with and applying operations on each copy) can be used to correct errors that occur during computation.

Ideally, quantum computations would also not be affected by noise. Fault-tolerant quantum computing refers to the ability of a quantum computer to perform accurate computations without being affected by errors. However, in quantum computing, errors are much more common due to the inherent fragility of quantum states and the effect of noise on qubits. In a fault-tolerant quantum computer, errors are detected and corrected using sophisticated error correction codes that encode quantum information redundantly. This redundancy allows for detection and correction of errors during computation.

If you want to dive deep into how quantum computers correct errors, we have a deep dive module available on IQM Academy (previous knowledge of implementing quantum algorithms with Python is required).

So, the term "Noisy Intermediate-Scale" also highlights the fact that current and near-term quantum computers are not yet powerful enough to perform fault-tolerant quantum computing as these codes require huge amounts of qubits, which are not available with the intermedia scale provided in the NISQ era. But these NISQ devices are still useful for exploring intermediate-scale problems that are beyond reach for classical computers.

Exploring new architectures for quantum computers – IQM Deneb

Not all quantum computers are equally adept at implementing error correction schemes. The efficiency of error correction is heavily dependent on the quantum computer's architecture, particularly the design of its QPU and the connectivity of its qubits. Some architectures offer advantages for specific algorithms while others offer more direct and efficient pathways for qubit interactions, facilitating simpler and more robust error correction methods.

While most quantum computers have a linear or 2D layout, IQM Deneb has a star topology 🌟. This means that all qubits are connected to a central element, a novel computational resonator. The long-range high-connectivity architecture of IQM Deneb paves the road for 2-10 times more efficient quantum error correction codes compared to standard implementations.

Learn more about Deneb and its novel computational resonator, here (previous knowledge of implementing quantum algorithms with Python is recommended for everything but the first page).

Conclusion

Despite these limitations, NISQ devices could still be capable of performing useful quantum computations. Therefore, current devices are being used to explore various quantum algorithms and applications for research and generating intellectual property. And with exciting new technologies like IQM Deneb on the horizon, the future of quantum computing is looking brighter than ever 🚀.