A Dynamic Test Oracle for Quantum Programs with Separable Output States

As quantum software engineering advances, testing techniques are required to assess the quality of quantum programs (QPs). In the test process, the test oracle is vital for determining whether the test result indicates a success or a failure. Most related works directly measure the output states and acquire the corresponding test results by comparing the output distribution with the expected one. While attention has been paid to the capability of fault detection, the guarantee for the correctness of the produced test results remains limited. Unlike classical programs (CPs), the output quantum states of QPs should be transformed into probabilistic classical outcomes through quantum measurement. This additional operation of measurement could cause a test oracle to yield the wrong test results. Especially for high-dimensional output spaces, numerous measurement outcomes are required to capture the distribution characteristics, threatening the effectiveness and cost-efficiency of test oracles. Hence, this paper proposes a novel specified test oracle DOSS employing a dynamic scheme to integrate a quantum algorithm (i.e., swap test) with the direct measurement mode. This innovative approach enables the validation of individual outputs rather than their distribution during the testing phase. Considering acceptable cost, DOSS decomposes the fully or partially separable output states to lower the dimensionality and simplify the quantum circuit for testing. Empirical studies demonstrate that DOSS generally gives more correct test results than baselines, and maintains reasonable cost on an ideal simulator. Besides, DOSS’s effectiveness with quantum noise involved is validated via three noisy simulators.