Einstein’s Struggles with Quantum Theory (eBook)

Dipankar Home is Professor of Physics at Bose Institute, Calcutta. Over the past two decades he has been working extensively on the fundamental aspects of quantum mechanics, especially on topics related to entanglement and quantum nonlocality, quantum communications, the measurement problem, quantum Zeno effect, quantum time distributions and nonstandard interpretations of quantum mechanics such as the Bohmian model. One area of his research has involved linking the foundational issues of quantum mechanics with realizable experiments. Home's earlier book Conceptual Foundations of Quantum Physics (Plenum, New York, 1997) was positively reviewed in various publications such as Physics Today, Progress in Quantum Electronics, and in The Times (London) Higher Education Supplement. Andrew Whitaker has been Professor of Physics at Queen's University Belfast since 1999. His early research was in the theory of pulsed nuclear magnetic resonance. In recent years he has been concerned with the foundations of quantum theory and has published over 50 papers in this area. He has had a special interest in the quantum Zeno effect, the interpretations of quantum theory and the Bohr-Einstein dispute. He has written several articles on Belfast-born John Bell.  In 1996 he published Einstein, Bohr and the Quantum Dilemma and in 2002 edited Physicists of Ireland: Passion and Precision with Mark McCartney.

Contents 6
Foreword 11
Preface 14
References 18
Setting the Scene 19
The Philosophical Background: Einstein and Mach 20
Introduction 20
Positivism and Ernst Mach 21
Mach’s Critique of Newton 23
Einstein and Mach—Part 1 25
Einstein and Mach—Part 2 29
Einstein and Mach—the Denouement 33
References 34
Einstein and Quantum Theory: The Early Years 37
Einstein and the Development of Quantum Theory 37
The Photon and Specific Heats 39
Spontaneous and Stimulated Emission Probability and Statistics
The Path to the New Quantum Theory 45
The New Quantum Theory: Bohr and Heisenberg 46
The New Quantum Theory: Einstein’s Contributions 48
References 52
Quantum Mechanics and its Fundamental Issues 54
Introduction 54
Some Preliminaries 55
The Uncertainty Principle 59
‘Time-Energy Uncertainty Principle’ 60
Pure and Mixed States 61
Statistical Properties of Pure States 62
Statistical Properties of Mixed States 63
Observable Distinction between a Pure and a Mixed State 63
Classical Realism or Macrorealism 65
Quantum Realism 65
The Quantum Measurement Problem 66
The Classical Limit Problem of Quantum Mechanics 68
The Limit Problem: Wave and Ray Optics 69
The Limit Problem: Special Relativity and Newtonian Mechanics 69
The Classical Limit Problem in Standard Quantum Mechanics 70
Wave-Particle Duality 71
References 72
The Standard Interpretation of Quantum Mechanics 74
Introduction 74
The Bohr–Heisenberg Version 76
The Ensemble Interpretation 79
Single System vis-à-vis Ensemble Interpretation 80
The Bohr–Heisenberg ‘Solution’ to the Quantum Measurement Problem 82
Position-Momentum Complementarity 83
Wave-Particle Complementarity 85
Bohr and the ‘Disturbance Interpretation’ 87
von Neumann and the Projection Postulate 88
von Neumann’s Impossibility ‘Proof’ 91
References 92
Interlude 95
Einstein Confronting Quantum Theory from 1925 96
Einstein’s Approaches to Quantum Theory 1925– 1935 97
Initial Impressions 97
Einstein’s Unpublished Paper on Hidden Variables 101
The Solvay Conference 1927—Main Proceedings and Einstein– Bohr Part I 103
The Solvay Conference 1930—Einstein–Bohr Part II 108
Einstein–Bohr: Argument and Concepts in the Early Parts of the Debate 109
Einstein’s Boxes 115
References 117
EPR and its Aftermath 119
Introduction 119
Einstein Locality and Bell Locality 122
Entanglement 123
Einstein’s Version of the EPR Argument 125
Einstein’s Version of the EPR Argument: Further Consideration 127
The Bohm Version of EPR 131
The Original EPR Argument of 1935 133
Bohr’s Response to EPR35 138
EPR—What did it Mean? 144
Einstein and Schrödinger: The 1935 Correspondence 148
Note added in proof 150
References 150
Einstein and the Macroscopic Limit of Quantum Mechanics 153
Introduction 153
Macrorealism: Examples 154
Macrorealism: Discussion 155
Particle in a Box 157
Dephasing of theWave-Packet 161
Localisation of theWave-Packet 162
Conclusions 163
References 164
Summary of Einstein’s Views 166
Did Einstein ‘Reject’ Quantum Theory? 166
Einstein’s Philosophical Position—General Remarks 170
Einstein’s Approach to the Copenhagen Interpretation 174
Einstein on Determinism 179
Einstein on Realism 183
Realism as a Programme 188
Einstein on Locality 193
Einstein’s Vision for Physics—the Unified Field Theory 196
Einstein and Ensembles 200
Einstein and the Bohm Theory 207
Realism, Determinism, Locality 210
References 213
Interlude 217
Denouement 219
Bell’s Contributions and Quantum Non- locality 220
Introduction 220
Limitation to von Neumann’s Theorem and Prelude to Bell’s Theorem 222
Bell’s Theorem 224
Bell’s Theorem Using Stochastic Hidden Variables 229
Contextuality 231
Signal Locality, and Parameter and Outcome Independence 232
General Remarks on Local Realism and Entanglement 235
Bell-type ArgumentsWithout Inequalities: Greenberger– Horne– Zeilinger 236
Bell-type ArgumentsWithout Inequalities: Hardy’s Argument 238
Experimental Tests of Bell-type Inequalities 240
Experimental Tests of Quantum Non-locality Without Inequalities 245
Quantum Teleportation 245
Bell and Einstein 248
Note added in proof 250
References 250
Non-standard Quantum Interpretations 256
Introduction 256
Many-Worlds Interpretation 257
Bohm’s Model: The Ontological Interpretation 259
Bohm’s Model: A Simple Illustrative Example 263
Bohm’s Model: Approach to the Measurement Problem 264
Dynamical Models of SpontaneousWave-Function Collapse 265
Consistent Histories and Decoherent Histories 268
Knowledge and Information Interpretations 270
Stochastic Interpretations 271
The Quantum State Diffusion Model 272
Many Hilbert Space Approach 273
Gravitationally InducedWave-Function Collapse Approach 274
Wave-Function Collapse Models Based on Irreversibility 276
Conclusions 277
References 277
Einstein and Quantum Information Theory 282
The Rise of Quantum Information Theory 282
Einstein and Quantum Information Theory 285
A Sketch of the Theory of Quantum Computation 288
The Deutsch Algorithm 293
Other Topics in Quantum Computation 296
Einstein and Quantum Computation 297
Quantum Cryptography 299
Note added in proof 303
References 303
Bridging the Quantum-Classical Divide 307
Introduction 307
Environment-induced Decoherence Schemes: Basic Ideas 307
Collision with External Environment Particles: Photons, Gas Molecules, etc. 311
Oscillator Model of the Environment 314
Assessment of the Decoherence Programme 315
Other Approaches to the Classical Limit 317
The h . 0 Limit 317
The N .8 Limit 320
Ehrenfest’s Theorem 321
The Quantum Theory of Macroscopic Systems 322
Conclusions 323
References 323
Interlude 326
Looking Forward 327
Quantum Foundations: General Outlook 328
Introduction 328
Macrorealism in Relation to Quantum Mechanics 329
The Leggett–Garg Inequality 331
Other Examples Testing Quantum Superpositions for Macrosystems 334
The Quantum Zeno Effect 336
The Quantum Zeno Effect: Experimental Test 339
The Quantum Zeno Effect: RecentWork 340
Time in Quantum Mechanics 340
References 344
Assessment of Einstein’s Views and Contributions 349
HowWould Einstein have Reacted to the Present Situation? 349
Summary and Assessment of Einstein’s Contributions 353
AThought Concerning Einstein’s Possible Choice of Interpretation 357
References 357
Epilogue 359
Name Index 361
Subject Index 369