Exploring Quantum Physics through Hands–on Projects

Build an intuitive understanding of the principles behind quantum mechanics through practical construction and replication of original experiments With easy–to–acquire, low–cost materials and basic knowledge of algebra and trigonometry, Exploring Quantum Physics through Hands–on Projects takes readers step by step through the process of re–creating scientific experiments that played an essential role in the creation and development of quantum mechanics. Presented in near chronological order—from discoveries of the early twentieth century to new material on entanglement—this book includes question– and experiment–filled chapters on: Light as a Wave Light as Particles Atoms and Radioactivity The Principle of Quantum Physics Wave/Particle Duality The Uncertainty Principle Schrödinger (and his Zombie Cat) Entanglement From simple measurements of Planck′s constant to testing violations of Bell′s inequalities using entangled photons, Exploring Quantum Physics through Hands–on Projects not only immerses readers in the process of quantum mechanics, it gives them insight into the history of the field—how the theories and discoveries apply to our world not only today, but also tomorrow. By immersing readers in groundbreaking experiments that can be performed at home, school, or in the lab, this first–ever, hands–on book successfully demystifies the world of quantum physics for all who seek to explore it—from science enthusiasts and undergrad physics students to practicing physicists and engineers.

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

DAVID PRUTCHI, PhD, is Vice President of Engineering at Impulse Dynamics. An adept do–it–yourselfer, he is dedicated to bringing cutting–edge experimental physics within the grasp of fellow science buffs. In addition to being the lead author of Design and Development of Medical Electronic Instrumentation (Wiley), he has published over 30 scientific publications and holds over 70 patents. SHANNI R. PRUTCHI is a high–school junior at Jack M. Barrack Hebrew Academy in Bryn Mawr, Pennsylvania. An avid science and engineering enthusiast, she conducts research with her father in the areas of radio astronomy and quantum physics.

“This unique book can also be highly recommended as supplementary reading, even in the absence of actual ‘hands–on’ participation in the many projects described.”  ( Contemporary Physics , 6 December 2013