Quantum information science [https://quantum.gov] has emerged as a promising area for the development of disruptive computing technologies. Since 2015, ASCR has organized several workshops that have indicated the potential of quantum computing for scientific applications [2 -5] and has supported basic research to improve all layers of the quantum software stack including algorithms, programming languages, error mitigation, and compilers. The progress has been remarkable, however, practical applications of quantum computing that improve time-to-solution, or power-to-solution, or accuracy of the results with respect to the best classical system have not yet been deployed. The 2023 Basic Research Needs Workshop in Quantum Computing and Networking [6] identified several priority research directions (PRDs); this FOA targets end-to-end software toolchains to program and control quantum systems and networks at scale (PRD1), quantum algorithms delivering quantum advantage (PRD2), and resilience through error detection, prevention, protection, mitigation, and correction (PRD4). These are key components for the development of a software ecosystem that must be ready to account for modularity and interoperability on one side, and for specialization and performance on another. Research proposed in response to this FOA must primarily focus on addressing one of the two topics described below: Topic 1 Modular Software Stack: The diversity of quantum computing architectures and hardware technologies is expected to persist into the foreseeable future; this is an important consideration that guides the advancement of computer science sought in this topic. The development of an integrated computational ecosystem requires a general-purpose quantum software stack that is adaptable to, and takes advantage of, multiple kinds of quantum hardware. We seek basic research in computer science and applied mathematics that: Addresses practical and fundamental bottlenecks that hinder modularity and potential synergy among selected hardware technologies; Pursues general approaches to integration that may remain relevant for future technologies; Devises ways to embed quantum processors in parallel and distributed computing models; and Integrates error management across the software stack. Topic 2 Quantum Utility: This topic aims to advance the research towards achievement and demonstration of quantum utility [1] by developing new algorithms and fine-tuning all levels of the software stack for a selected portfolio of promising problems within the ASCR mission. Applications should: Choose generalizable application-inspired target problems; Develop algorithms for optimized math kernels and math primitives for selected current (NISQ) and future quantum systems that significantly advance state-of-the-art performance for the selected target problems; Adapt, if needed, any level of the software stack for the specific target problems; and Estimate quantum resources by employing important complementary metrics, including energy-to-solution. Verification protocols and tools are important for both Topic 1 and Topic 2 and should be discussed in the application. Applicants must choose and specify Topic 1 or Topic 2 as the focus of their application. In the choice of Topic 1 or 2, proposed research is encouraged to consider multiple metrics, such as qubit count, gate fidelity, and qubit connectivity.