Quantum Computing with Superconducting Qubits and Cavities: Concepts and Technology

This book explores the physical principles, theoretical foundations, and engineering technologies underlying quantum computing based on superconducting qubits and microwave cavities. The authors introduce the fundamentals of quantum computation, covering concepts such as qubits, coherence and decoherence, quantum gates, entanglement, and measurement. Topics including quantum errors, error correction, and qudits are also discussed to familiarize readers with the principles of quantum information processing and the physical requirements for its implementation. A substantial part of the book is devoted to the design and operation of superconducting qubits, particularly transmon qubits, and their interaction with high-quality microwave cavities. The authors examine the physical principles of superconducting circuits, quantum oscillators, LC circuits, Josephson junctions, and cavity–transmon architectures. The book also addresses quantum computation using bosonic modes, Fock states, quantum memories, and bosonic encoding. Bosonic error-correcting codes, including cat, binomial, and Gottesman–Kitaev–Preskill (GKP) codes, are discussed in detail. Another major focus of the book is the role of materials science, fabrication techniques, and surface treatments in improving the coherence times of qubits and cavities. By analyzing energy-loss mechanisms, factors limiting quantum state lifetimes, and the requirements for scalable processor development, the authors clarify the relationship between material properties, hardware design, and computational performance. In addition to providing theoretical foundations, this work offers the technical knowledge required to understand and analyze advanced superconducting qubit technologies and cavity-based architectures, making it valuable for students, engineers, and researchers.