Preface ......................................................... v
Foreword ....................................................... ix
1 An Inconvenient Principle .................................... 1
1.1 Waves in classical physics .............................. 2
1.2 The Mach-Zehnder interferometer ......................... 6
1.3 Photons ................................................. 8
1.4 Photons in the Mach-Zehnder interferometer ............. 15
1.5 The Mach-Zehnder interferometer revisited .............. 18
1.6 Quantum particles ..................................... 21
1.7 Delayed choice and interaction-free measurement ........ 24
1.8 Further reading ........................................ 28
2 Secure Communications ....................................... 29
2.1 Classical cryptography: Secret key and public key ...... 29
2.2 Light polarization ..................................... 33
2.3 Photon polarization .................................... 35
2.4 The BB84 protocol of quantum cryptography .............. 39
2.5 Further reading ........................................ 43
3 Einstein, Bohr, and Bell .................................... 45
3.1 Superluminal communications? ........................... 46
3.2 A remarkable inequality ................................ 48
3.3 Quantum physics and entanglement ....................... 50
3.4 Bell's non-locality and experiment ..................... 54
3.5 Further reading ........................................ 59
4 Atoms, Light, and Lasers .................................... 61
4.1 Classical particles and classical waves on a line ...... 62
4.2 A quantum particle in a potential well ................. 65
4.3 Heisenberg inequalities and energy levels .............. 67
4.4 Atoms .................................................. 71
4.5 Lasers ................................................. 74
4.6 Further reading ........................................ 80
5 Cold Atoms .................................................. 81
5.1 What is temperature? ................................... 82
5.2 Cooling atoms .......................................... 86
5.3 Bose-Einstein condensates .............................. 97
5.4 Further reading ....................................... 104
6 The Kingdom of Semiconductors .............................. 105
6.1 Conductors and insulators ............................. 106
6.2 Semiconductors ........................................ 112
6.3 Interaction with an electromagnetic field ............. 116
6.4 Heterojunctions ....................................... 118
6.5 Further reading ....................................... 123
7 Relativistic Quantum Physics ............................... 125
7.1 Relativistic quantum field theory ..................... 125
7.2 The standard model of particle physics ................ 135
7.3 Quantum gravity ....................................... 142
7.4 Further reading ....................................... 147
8 Towards a Quantum Computer? ................................ 149
8.1 Bits and quantum logic gates .......................... 150
8.2 Quantum algorithms .................................... 156
8.3 Quantum algorithms and algorithmic complexity ......... 161
8.4 Physical realizations ................................. 163
8.5 Further reading ....................................... 165
9 The Environment is Watching ................................ 167
9.1 Decoherence: An elementary example .................... 168
9.2 Environment and decoherence ........................... 172
9.3 Further reading ....................................... 179
10 Interpretations ............................................ 181
10.1 The Copenhagen interpretation ......................... 182
10.2 von Neumann's theory .................................. 188
10.3 The measuring apparatus is macroscopic ................ 193
10.4 Non-standard interpretations .......................... 196
10.5 Conclusion ............................................ 200
10.6 Further reading ....................................... 201
11 Appendices ................................................. 203
References ................................................. 231
Index ......................................................... 235
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