Exploring Quantum Physics through Hands-on Projects

Introduction xi

Prologue xv

Important Disclaimer and Warnings xix

Acknowledgments xxiii

About the Authors xxv

1 LIGHT AS AWAVE 1

Newton's View: Light Consists of Particles 1

Young's Interference of Light 3

Automatic Scanning of Interference Patterns 6

The Final Nail in the Coffin for Newton's Theory of Light 8

Light as an Electromagnetic Wave 9

Polarization 11

Optics with 3-cm Wavelength "Light" 11

Real-World Behaviors 16

Double-Slit Interference with Microwaves 17

The Doppler Effect 18

Experiments and Questions 20

2 LIGHT AS PARTICLES 23

The Seed of Quantum Physics: Planck's Formula 27

The Photoelectric Effect 28

Can we Detect Individual Photons? 36

Low-Cost PMT Power Supplies 38

Listening to Individual Photons 41

Where does this Leave Us? 45

Experiments and Questions 45

3 ATOMS AND RADIOACTIVITY 49

The Need for Vacuum 49

The Mechanical Vacuum Pump 51

The Vacuum Gauge 53

A Very-High-Voltage Power Supply 56

A Vacuum Tube Legow Set 56

Phosphor Screens 59

The Electron Gun 60

The Discovery of the Electron 61

Cathode-Ray Tubes 63

Thomson's First 1897 Experiment-Negative Charge and Rays are Joined Together 65

Thomson's Second Experiment-Electrostatic Deflection of Cathode Rays 67

Thomson and the Modern CRT 69

Thomson's Third Experiment-Mass-to-Charge Ratio of the Electron 72

Measuring e/m with our CRT 74

A Magical Measurement of e/m 77

Thomson's "Plum Pudding" Model of the Atom 79

Geiger-Mu¨ller Counter 80

a, b, and g 89

The Nature of Beta Radiation 92

The Ionizing Power of Alpha 92

What are Alpha Particles? 95

Rutherford's Alpha-Scattering Experiment 96

Rutherford's Planetary Model of the Atom 102

Experiments and Questions 103

4 THE PRINCIPLE OF QUANTUM PHYSICS 107

Emission Spectroscopy 107

Bohr's Spark of Genius 113

Orbitals and Not Orbits 115

Quantization-The Core of Quantum Physics 117

Experiments and Questions 118

5 WAVE-PARTICLE DUALITY 121

Gamma-Ray Spectrum Analysis 122

What is the Nature of Light? 126

Two-Slit Interference with Single Photons 128

Imaging Single Photons 133

The Answer: Complementarity 135

Matter Waves 137

Matter Waves and the Bohr Atom 137

Experimental Confirmation of De Broglie's Matter Waves 138

Two-Slit Interference with Single Electrons 142

A Simple TEM 144

Blurring the Line Between Quantum and Classical 148

Particle-Wave Duality in the Macroscopic World 148

Experiments and Questions 149

6 THE UNCERTAINTY PRINCIPLE 151

Wavefunctions 151

The Uncertainty Principle 153

Experimental Demonstration of the Uncertainty Principle 155

Time-Energy Uncertainty 159

Fourier Analysis 159

Bye, Bye Clockwork Universe 163

Experiments and Questions 165

7 SCHRO¨ DINGER (AND HIS ZOMBIE CAT) 167

Real-World Particle in a Box 171

Quantum Tunneling 174

Quantum Tunneling Time 178

Many-Worlds Interpretation 183

Schro¨dinger's Cat in the Lab 184

Beam Splitters 186

Who Rolls the Dice? 190

The Mach-Zehnder Interferometer 192

"Which-Way" Experiments 197

The Quantum Eraser 199

Experiments and Questions 200

8 ENTANGLEMENT 203

Bell's Inequalities 205

An Entangled-Photon Source 211

Detecting Entangled Photons 214

High-Purity Single-Photon Source 219

Testing Bell's Inequality 220

Closing the Loopholes 225

The Age of Quantum Information 226

A Quantum Random-Number Generator 228

Quantum Information 229

Quantum Teleportation 230

Faster-Than-Light Communication 236

Quantum Cryptography 237

Quantum Computing and Technologies for the Future 240

Experiments and Questions 242

REFERENCES 245

SOURCES FOR MATERIALS AND COMPONENTS 249

ABBREVIATIONS 255

INDEX 257