This two-volume set CCIS 2743 and 2744 constitutes the refereed proceedings of the 1st International Conference on Quantum Engineering Sciences and Technologies for Industry and Services, QUEST-IS 2025, held in Paris, France, during December 1?4, 2025. The 68 full papers included in this book were carefully reviewed and selected from 120 submissions. They were organized in topical sections as follows:  Part I: Enabling Technologies; Quantum Sensors Applications; Quantum Sensors in Detection and Sensing; Quantum Communications ? Test Platforms for Qkd; Quantum Key Distribution; Towards A Quantum Internet Infrastructure; Quantum Algorithms, Computing & Simulation ? Benchmarking: Methods & Applications; Error Mitigation & Fidelity; and Quantum Algorithms for Finance & Industry Part II: Quantum Algorithms, Computing & Simulation ? Quantum Algorithms for Finance & Industry; Scheduling, Logistics & Complex Systems; Quantum Machine Learning; Physics & Engineering Applications; Simulation & Quantum Chemistry; Hardware & Architectures; and Specialized Applications & Security.