Quantum computers leverage the principles of quantum mechanics to execute operations. They require quantum programs that define operations on quantum bits (qubits), the fundamental units of computation. Unlike traditional software development, the process of creating and debugging quantum programs requires specialized knowledge of quantum computation, making the development process more challenging.

When a bug is detected by testing a quantum program on a quantum computer, we want to determine its location to fix it. To locate the bug, the quantum program is divided into several segments, and each segment is tested. However, to prepare a quantum state that is input to a segment, it is necessary to execute all the segments ahead of that segment in a quantum computer. This means that the cost of testing each segment depends on its location. We can also locate a buggy segment only if it is confirmed that there are no bugs in all segments ahead of that buggy segment. Since a quantum program is tested statistically on the basis of measurement results, there is a tradeoff between testing accuracy and cost. These characteristics are unique to quantum programs and complicate locating bugs. We propose an efficient bug-locating method consisting of four approaches, i.e., cost-based binary search, early determination, finalization, and looking back, which take these characteristics into account. We present experimental results indicating that the proposed method can reduce bug-locating cost, represented as the number of executed quantum gates, compared with naive methods that do not use the four approaches. The limitations and usefulness of the proposed method are also discussed on the basis of the experimental results.

Quantum computers, which utilize the principles of quantum mechanics, are expected to be applied to a wide range of fields. With the advancement of quantum computer development, a lot of quantum software, which enables the operation of quantum computers, has been developed. It has a distinct nature (e.g., superposition and entanglement of qubits) compared to traditional software, leading to the unique challenges of its development. While prior studies have clarified and defined some unique challenges of quantum software, many remain unclear due to limited research. In this study, we conducted an empirical study of Self-Admitted Technical Debt (SATD) for quantum software. SATD is a type of technical debt, a problem in the code that the developer is aware of. Hence, we conjecture that analyzing SATDs can reveal the unique challenges developers face when developing quantum software. We manually coded 202 comments from the Python® files of the 61 open-source quantum software on GitHub®. The 202 comments correspond to a 95% confidence level with a 5% confidence interval, as in previous studies. The results showed that 88 comments (45.6% of all SATD comments) were quantum-specific SATDs (QSATDs), which require knowledge of quantum computation to repay. Furthermore, we propose a taxonomy for QSATDs. This taxonomy, which consists of four main categories and eight subcategories, classifies QSATDs in terms of quantum-specific aspects such as circuit implementation, backend, and algorithms. Our empirical results are beneficial for quantum software developers, helping them understand implementation areas that require attention. For researchers, our results promote further research, including the exploration of challenges in QSATD repayment.

Photoacoustic (PA) or optoacoustic imaging can visualize tissue-optical absorbers, especially hemoglobin, with optical contrast and ultrasound (US)-like resolution and imaging depth. Since both PA and US imaging involves US detection, it is straightforward to develop dual-mode imaging systems with unprecedented functional and structural imaging capabilities. Researchers have already demonstrated the potential of utilizing this complementary contrast for several animal imaging experiments and early clinical pilot studies. PA imaging conventionally uses slow, bulky and high-priced lasers as excitation sources. Use of these high-power pulsed lasers is hindering the clinical translation process of this imaging modality with tremendous potential. Advances in solid-state device technology have recently resulted in the development of a new class of high-power light emitting diodes (LEDs) that can be used as fast, robust and affordable pulsed excitation sources for PA imaging. In this paper, we review multiple LED-based PA/US imaging implementations (commercial and lab-made systems) and demonstrate its functional, molecular and structural imaging capabilities using several clinical/preclinical imaging examples. Specific focus will be given to 2D and 3D superficial vasculature and oxygen saturation imaging in multiple in vivo clinical and preclinical studies.

WS-I's basic security profile (BSP) defines best practice guidelines for secure Web services communications, enabling interoperability between vendors. However it is difficult for developers to know if their SOA solutions are in fact compliant to these guidelines. In this paper, we discuss methods to assess compliance against BSP. We have implemented runtime validation of SOAP messages to check for compliance against BSP, a method implied by the BSP definition itself. Additionally, we have implemented a novel approach to statically validate WS security policies against BSP using Schematron. From our experiments dynamic validation for BSP compliance offers greater coverage but results in a significant overhead, while static validation is limited in its scope but extremely valuable since under reasonable assumptions it provides assurances about compliance prior to deployment. We conclude with a summation of our results and lessons for SOA practitioners.

We propose a new task scheduling algorithm for timed-functional simulation of concurrent software tasks. It attains efficiency by reducing the frequency of context-switching between concurrent tasks. It also provides a high-degree of portability in the sense that it only needs the underlying system to support a very small number of primitives. We provide a concrete implementation built on top of the SystemC scheduler and show some results of preliminary evaluation

Current standardization efforts on Web service interoperability provide ways to compose Web services distributed across heterogeneous network environments. Unfortunately, this has been attained at the expense of efficiency, that is, substantial SOAP communication overheads have negative impact on the performance of Web services. To resolve this and improve performance, we have developed a new mechanism for hiding communication latency by means of parallelization of service invocations within a composite Web service. Our mechanism exploits static analysis techniques to keep track of the behavioral states of Web service components through their execution steps and statically detects whether service invocations may have dependencies with each other at certain states. The analysis can thus guarantee the parallelization will not affect the result Of computation. Evaluation shows strong potential of our mechanism: it substantially improves the performance of composite Web services based on a real-world example of Portfolio optimization.