Detecting and Tolerating Faults in Hybrid Quantum Software Systems Using Architectural Redundancy

Quantum computers, especially in the NISQ-Era, exhibit gate and measurement errors resulting in faulty executions. This leads to inaccurate and unreliable results, which are propagated to the remaining components of the software system in which the quantum component is embedded. In this paper, we adopt established and well-known architectural patterns from software engineering for fault-tolerant systems to deal with NISQ-induced uncertainties and to gain more accurate results. We adopt three existing patterns, namely the Voter, Comparison and Sparing pattern. We show how these patterns can be applied in the quantum computing setting and what modifications are necessary in this context. We evaluated our approach on an established benchmark for quantum circuits. The main focus of the evaluation was on whether (redundancy-based) fault-tolerant patterns outperform single instances of quantum components and whether the extra effort patterns entail is justified. Our results showed that each pattern provides an improvement over the average single component.