Hardware & Errors
Fault Tolerance
The property of a quantum computer being able to perform reliable computation despite the presence of errors in individual components.
Definition
Fault tolerance describes a quantum computing system's ability to continue functioning correctly even when individual physical qubits or gates experience errors, by using quantum error correction to detect and fix problems faster than they accumulate.
Technical Definition
The fault-tolerance threshold theorem establishes that, as long as physical error rates are below a certain threshold, increasing the size of an error-correcting code (and the redundancy it provides) can suppress logical error rates arbitrarily, in principle enabling arbitrarily long, reliable computation.
Visual Explanation: An Analogy
Think of fault tolerance like a well-designed building with redundant support structures — even if a few support beams develop minor cracks, sufficient redundancy and reinforcement keep the building safely standing rather than collapsing.
Real-World Use Cases
- The ultimate engineering goal of quantum hardware development, beyond today's NISQ-era machines
- Google's Willow processor's below-threshold error scaling result was a significant step toward demonstrating fault tolerance is achievable