Noah Daniel Hegerland Oldfield

• Oldfield, Noah Daniel Hegerland; Laaber, Christoph; Yue, Tao & Ali, Shaukat (2025). Faster and Better Quantum Software Testing through Specification Reduction and Projective Measurements. ACM Transactions on Software Engineering and Methodology. ISSN 1049-331X. 34(7). doi: 10.1145/3714468. Full text in Research Archive Show summary

  Quantum computing (QC) promises polynomial and exponential speedups in many domains, such as unstructured search and prime number factoring. However, quantum programs yield probabilistic outputs from exponentially growing distributions and are vulnerable to quantum-specific faults. Existing quantum software testing (QST) approaches treat quantum superpositions as classical distributions. This leads to two major limitations when applied to quantum programs: (1) an exponentially growing sample space distribution and (2) failing to detect quantum-specific faults such as phase flips. To overcome these limitations, we introduce a QST approach, which applies a reduction algorithm to a quantum program specification. The reduced specification alleviates the limitations (1) by enabling faster sampling through quantum parallelism and (2) by performing projective measurements in the mixed Hadamard basis. Our evaluation of 143 quantum programs across four categories demonstrates significant improvements in test runtimes and fault detection with our reduction approach. Average test runtimes improved from 169.9 s to 11.8 s, with notable enhancements in programs with large circuit depths (383.1 s to 33.4 s) and large program specifications (464.8 s to 7.7 s). Furthermore, our approach increases mutation scores from to , effectively detecting phase flip faults that non-reduced specifications miss. These results underline our approach's importance to improve QST efficiency and effectiveness.

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• Oldfield, Noah (2023). Improved Runtime and Fault-Detection in Quantum Software Testing through Factorized Program Specifications. Full text in Research Archive
• Oldfield, Noah (2023). Improved Runtime and Fault-Detection in Quantum Software Testing through Factorized Program Specifications. Full text in Research Archive
• Oldfield, Noah (2023). Quantum Computing - an army of Schrödinger's cats is heading our way. Full text in Research Archive Show summary

  Quantum Computing (QC) is maturing to become a reality as a large amount of money worldwide is being poured into building quantum computers with varying technologies, such as superconducting, optics-based, and ion-trapping. Indeed, having functional, powerful, and error-free quantum computers together with relevant development platforms is essential. However, the breakthrough applications promised by QC, e.g., in medicine, healthcare, finance, and simulations discovery, finance, are empowered with quantum software. Therefore, there is a need for methods for efficient and intuitive development of quantum software for quantum computers to build QC applications. This lighting talk will start with a brief introduction to quantum computing, including the state of current quantum computers, QC platforms, programming languages, and development platforms. Next, the talk will dig deep into the current practice of programming quantum computers as low-level circuits. Subsequently, the talk will provide ideas on how the current practice can be improved to enable the masses to program quantum computers as opposed to the current practice where only specialists program quantum computers. In addition, the talk will present challenges in testing QC applications to ensure their correctness. Finally, the talk will provide a teaser of quantum software testing tools developed by our team. Such tools are the first in the world to automate the testing of quantum software.

• Wang, Xinyi; Oldfield, Noah & Mendiluze, Eñaut (2022). Quantum Software Testing Work in ComplexSE. Full text in Research Archive
• Oldfield, Noah; Yue, Tao & Ali, Shaukat (2022). Investigating Quantum Cause-Effect Graphs. Full text in Research Archive Show summary

  Cause-effect graphs have shown promising results in identifying relations among causes and effects of classical software systems, followed by designing effective test cases from them. Towards this end, we investigate the use of cause-effect graphs for quantum programs. Classical cause-effect graphs apply classical logic (e.g., AND, OR) to express these relations, which might not be practical for describing similar relations in quantum programs due to quantum superposition and entanglement. Thus, we propose an extension of cause-effect graphs, where quantum logic inspired functions (e.g., Hadamard) and their generalizations are defined and applied. Moreover, we present a metamodel describing various forms of cause-effect graphs. Finally, we demonstrate a possible method for generating test cases from a quantum cause-effect graph applied to a Bell state quantum program. Lastly, the design and utility of the resulting testing method is discussed, along with future prospects for general quantum cause-effect graphs.

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