Exploring Quantum Physics through Hands-on Projects

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 provides 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.

Prologue xv

Important Disclaimer and Warnings xix

Acknowledgments xxiii

About the Authors xxv

1LIGHT 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

2LIGHT 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

3ATOMS 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

4THE 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

5WAVE–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

6THE 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

7SCHRO¨ 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

8ENTANGLEMENT 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.