Quantum computing creates new opportunities, but building and operating a quantum cloud service remains a complex challenge, often relying on proprietary, black-box solutions. To bridge this gap, we introduce OQTOPUS (Open Quantum Toolchain for OPerators and USers) [1], a comprehensive open-source software stack designed to build and manage full-scale quantum computing systems. OQTOPUS provides a complete cloud architecture for quantum computers, covering three critical layers: 1.Frontend Layer: Web-based interfaces and SDKs that allow users to easily design and submit quantum circuits. 2.Cloud Layer: A scalable management system for users, jobs, and devices, designed to be deployable on public clouds (see oqtopus-cloud [2]). 3.Backend Layer: The core execution engine that handles circuit transcoding, error mitigation, and low-level device control, utilizing modular tools such as OQTOPUS Engine [3] and Tranqu [4].

Developed in collaboration with The University of Osaka, Fujitsu Limited, Systems Engineering Consultants Co., LTD. (SEC), and TIS Inc. (TIS) is already powering operational superconducting quantum computers. This talk will detail the modular architecture of OQTOPUS, demonstrating how developers and researchers can use it to construct their own quantum cloud platforms, customize compilation strategies, and experiment with hybrid quantum-classical workflows. Join us to learn how OQTOPUS is democratizing access to the deepest layers of quantum infrastructure.

Project Links: [1] OQTOPUS Organization: https://github.com/oqtopus-team [2] Cloud Layer: https://github.com/oqtopus-team/oqtopus-cloud [3] OQTOPUS Engine: https://github.com/oqtopus-team/oqtopus-engine [4] Tranqu: https://github.com/oqtopus-team/tranqu