Macroscopic quantum phenomena are particularly important when considering the problem of Schroedinger's cat. This book contains a coherent and self-contained account of such phenomena, focusing on the central role played by macroscopic quantum tunneling. Beginning with an explanation of the nature and significance of the cat problem, Shin Takagi introduces the concept of macroscopic quantum tunneling. He deals with typical examples in detail, elucidating how quantum mechanical coherence may be lost (so-called 'decoherence') or how it may be maintained despite the effects of environment and measurement processes. Recent experimental and theoretical advances are discussed, and the remaining problems described. The final chapter describes an experiment to decide between quantum mechanics and macrorealism in the light of Einstein's moon. Assuming only a knowledge of elementary quantum mechanics, this book emphasises conceptual aspects rather than technical details. It provides a firm introduction to the subject for graduate students and researchers.

• 1. Introduction
• 2. Overview of macroscopic quantum tunneling
• 3. Some candidate systems for macroscopic quantum tunneling
• 4. Environmental problems
• 5. Harmonic environment
• 6. Quantum resonant oscillation in the harmonic environment
• 7. Quantum decay in the harmonic environment
• 8. General versus harmonic environments
• 9. The cat in the moonlight
• Appendix A. Euclidean space and Hilbert space
• Appendix B. Virtual ground state of a system of a single degree of freedom and its decay
• Appendix C. Functional derivative
• Appendix D. Miscellanea about spin
• References.