Abstract As a new research area, quantum software testing lacks systematic testing benchmarks to assess testing techniques’ effectiveness. Recently, some open-source benchmarks and mutation analysis tools have emerged. However, there is insufficient evidence on how various quantum circuit characteristics (e.g., circuit depth, number of quantum gates), algorithms (e.g., Quantum Approximate Optimization Algorithm), and mutation characteristics (e.g., mutation operators) affect the detection of mutants in quantum circuits. Studying such relations is important to systematically design faulty benchmarks with varied attributes (e.g., the difficulty in detecting a seeded fault) to facilitate assessing the cost-effectiveness of quantum software testing techniques efficiently. To this end, we present a large-scale empirical evaluation with more than 700K faulty benchmarks (quantum circuits) generated by mutating 382 real-world quantum circuits. Based on the results, we provide valuable insights for researchers to define systematic quantum mutation analysis techniques. We also provide a tool to recommend mutants to users based on chosen characteristics (e.g., a quantum algorithm type) and the required difficulty of detecting mutants. Finally, we also provide faulty benchmarks that can already be used to assess the cost-effectiveness of quantum software testing techniques.

Background: Quantum computing is a rapidly growing new programming paradigm that brings significant changes to the design and implementation of algorithms. Understanding quantum algorithms requires knowledge of physics and mathematics, which can be challenging for software developers. Aims: In this work, we provide a first analysis of how LLMs can support developers’ understanding of quantum code. Method: We empirically analyse and compare the quality of explanations provided by three widely adopted LLMs (Gpt3.5, Llama2, and Tinyllama) using two different human-written prompt styles for seven state-of-the-art quantum algorithms. We also analyse how consistent LLM explanations are over multiple rounds and how LLMs can improve existing descriptions of quantum algorithms. Results: Llama2 provides the highest quality explanations from scratch, while Gpt3.5 emerged as the LLM best suited to improve existing explanations. In addition, we show that adding a small amount of context to the prompt significantly improves the quality of explanations. Finally, we observe how explanations are qualitatively and syntactically consistent over multiple rounds. Conclusions: This work highlights promising results, and opens challenges for future research in the field of LLMs for quantum code explanation. Future work includes refining the methods through prompt optimisation and parsing of quantum code explanations, as well as carrying out a systematic assessment of the quality of explanations.

Given that quantum software testing is a new area of research, there is a lack of benchmark programs and bugs repositories to assess the effectiveness of testing techniques. To this end, quantum mutation analysis focuses on systematically generating faulty versions of Quantum Programs (QPs), called mutants, using mutation operators. Such mutants can be used as benchmarks to assess the quality of test cases in a test suite. Thus, we present Muskit - a quantum mutation analysis tool for QPs coded in IBM's Qiskit language. Muskit defines mutation operators on gates of QPs and selection criteria to reduce the number of mutants to generate. Moreover, it allows for the execution of test cases on mutants and generation of results for test analyses. Muskit is provided as command line interface, GUI, and web application. We validated Muskit by using it to generate and execute mutants for four QPs. Muskit code: https://github.com/Simula-COMPLEX/muskitWeb app: https://qiskitmutantcreatorsrl.pythonanywhere.com/YouTube Video: EbPHJOK_AEA Artifact Available: https://doi.org/10.5281/zenodo.5288917