Decoherence (eBook)

Maximilian Schlosshauer is an internationally recognized researcher in the foundations of quantum mechanics in general and in quantum decoherence in particular. After completing his undergraduate education at Freiburg University, Germany, he graduated from Lund University, Sweden, with a Master of Science degree in 2001. He received a Ph.D. degree in Physics from the University of Washington in Seattle in 2005. His postgraduate research (with Arthur Fine) was focused on decoherence and the quantum-to-classical transition. He is currently an Australian Research Council Postdoctoral Fellow in the Department of Physics at the University of Melbourne, Australia. Besides his interest in decoherence and the foundations of quantum mechanics, he has also contributed important research in theoretical biophysics.

Preface 7
Contents 11
1 Introducing Decoherence 16
2 The Basic Formalism and Interpretation of Decoherence 28
2.1 The Concept and Interpretation of Quantum States 29
2.2 The Superposition Principle 35
2.3 Quantum Entanglement 43
2.4 The Concept and Interpretation of Density Matrices 48
2.5 The Measurement Problem and the Quantum- to- Classical Transition 64
2.6 Which-Path Information and Environmental Monitoring 75
2.7 Decoherence and the Local Damping of Interference 83
2.8 Environment-Induced Superselection 86
2.9 Redundant Encoding of Information in the Environment and “ Quantum Darwinism” 100
2.10 A Simple Model for Decoherence 103
2.11 Decoherence Versus Dissipation 108
2.12 Decoherence Versus Classical Noise 110
2.13 Virtual Decoherence and Quantum “Erasure” 113
2.14 Resolution into Subsystems 116
2.15 Formal Tools and Their Interpretation 118
2.16 Summary 127
3 Decoherence Is Everywhere: Localization Due to Environmental Scattering 130
3.1 The Scattering Model 134
3.2 Calculating the Decoherence Factor 137
3.3 Full Versus Partial Which-Path Resolution 143
3.4 Decoherence Due to Scattering of Thermal Photons and Air Molecules 147
3.5 Illustrating the Dynamics of Decoherence 154
3.6 Summary 165
4 Master-Equation Formulations of Decoherence 167
4.1 General Formalism 168
4.2 The Born–Markov Master Equation 169
4.3 Master Equations in the Lindblad Form 179
4.4 Non-Markovian Dynamics 183
5 A World of Spins and Oscillators: Canonical Models for Decoherence 185
5.1 Mapping onto Canonical Models 187
5.2 Quantum Brownian Motion 192
5.3 The Spin–Boson Model 221
5.4 Spin-Environment Models 236
5.5 Summary 251
6 Of Buckey Balls and SQUIDs: Observing Decoherence in Action 256
6.1 The First Milestone: Atoms in a Cavity 257
6.2 Interferometry with C70 Molecules 271
6.3 SQUIDs and Other Superconducting Qubits 283
6.4 Other Experimental Domains 295
6.5 Outlook 302
7 Decoherence and Quantum Computing 305
7.1 A Brief Overview of Quantum Computing 306
7.2 Decoherence Versus Controllability in Quantum Computers 313
7.3 Decoherence Versus Classical Fluctuations 314
7.4 Quantum Error Correction 316
7.5 Quantum Computation on Decoherence- Free Subspaces 333
7.6 Summary and Outlook 339
8 The Role of Decoherence in Interpretations of Quantum Mechanics 341
8.1 The Standard and Copenhagen Interpretations 342
8.2 Relative-State Interpretations 348
8.3 Modal Interpretations 356
8.4 Physical Collapse Theories 360
8.5 Bohmian Mechanics 366
8.6 Summary 369
9 Observations, the Quantum Brain, and Decoherence 371
9.1 The Role of the Observer in Quantum Mechanics 371
9.2 Quantum Observers and the Von Neumann Chain 373
9.3 Decoherence in the Brain: The Brain as a Quantum Computer? 377
9.4 “Subjective” Resolutions of the Measurement Problem 387
Appendix: The Interaction Picture 391
References 395
Index 420