Book contents
- Frontmatter
- Contents
- List of contributors
- Foreword
- Editors' preface
- Preface
- Acknowledgments
- Part I An overview of the contributions of John Archibald Wheeler
- Part II An historian's tribute to John Archibald Wheeler and scientific speculation through the ages
- Part III Quantum reality: theory
- 3 Why is nature described by quantum theory?
- 4 Thought-experiments in honor of John Archibald Wheeler
- 5 It from qubit
- 6 The wave function: it or bit?
- 7 Quantum Darwinism and envariance
- 8 Using qubits to learn about “it”
- 9 Quantum gravity as an ordinary gauge theory
- 10 The Everett interpretation of quantum mechanics
- Part IV Quantum reality: experiment
- Part V Big questions in cosmology
- Part VI Emergence, life, and related topics
- Appendix A Science and Ultimate Reality Program Committees
- Appendix B Young Researchers Competition in honor of John Archibald Wheeler for physics graduate students, postdoctoral fellows, and young faculty
- Index
6 - The wave function: it or bit?
from Part III - Quantum reality: theory
Published online by Cambridge University Press: 29 March 2011
- Frontmatter
- Contents
- List of contributors
- Foreword
- Editors' preface
- Preface
- Acknowledgments
- Part I An overview of the contributions of John Archibald Wheeler
- Part II An historian's tribute to John Archibald Wheeler and scientific speculation through the ages
- Part III Quantum reality: theory
- 3 Why is nature described by quantum theory?
- 4 Thought-experiments in honor of John Archibald Wheeler
- 5 It from qubit
- 6 The wave function: it or bit?
- 7 Quantum Darwinism and envariance
- 8 Using qubits to learn about “it”
- 9 Quantum gravity as an ordinary gauge theory
- 10 The Everett interpretation of quantum mechanics
- Part IV Quantum reality: experiment
- Part V Big questions in cosmology
- Part VI Emergence, life, and related topics
- Appendix A Science and Ultimate Reality Program Committees
- Appendix B Young Researchers Competition in honor of John Archibald Wheeler for physics graduate students, postdoctoral fellows, and young faculty
- Index
Summary
Introduction
Does Schrödinger's wave function describe physical reality (“it” in John Wheeler's terminology (Wheeler 1994)) or some kind of information (“bit”)? The answer to this question must crucially depend on the definition of these terms. Is it then merely a matter of words? Not quite – I feel. Inappropriate words may be misleading, while reasonably chosen terms are helpful.
A bit is usually understood as the binary unit of information, which can be physically realized in (classical) computers, but also by neuronal states of having fired or not. This traditional physical (in particular, thermodynamical) realization of information (“bit from it”) has proven essential in order to avoid paradoxes otherwise arising from situations related to Maxwell's demon. On the other hand, the concept of a bit has a typical quantum aspect: the very word quantum refers to discreteness, while, paradoxically, the quantum bit is represented by a continuum (the unit sphere in a two-dimensional Hilbert space) – more similar to an analog computer. If this quantum state describes “mere information,” how can there be real quantum computers that are based on such superpositions of classical bits?
The problematic choice of words characterizing the nature of the wave function (or a general “quantum state”) seems to reflect the common uneasiness of physicists, including the founders of quantum theory, about its fundamental meaning. However, it may also express a certain prejudice.
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- Science and Ultimate RealityQuantum Theory, Cosmology, and Complexity, pp. 103 - 120Publisher: Cambridge University PressPrint publication year: 2004
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