The theoretical minimum
Content
- Preface
- Introduction
- Introduction
- Systems and research
- Quantum states
- Principles of quantum mechanics
- Time and change
- Uncertainty and time dependence
- System integration: Integration
- More about navigation
- Particles and waves
- Important parts
- Harmonic oscillator
- Annex
- Phone book
Preface
Albert Einstein, widely regarded as the father of quantum mechanics, harbored a complex relationship with the subject. His conversations with Niels Bohr (Bohr’s acceptance of quantum mechanics and Einstein’s deep skepticism) are famous in the history of science. Most physicists generally accept that Bohr prevailed and Einstein lost. I, along with an increasing number of physicists, believe that this attitude fails to adequately honor Einstein’s ideas.
Both Bohr and Einstein were modest men. Einstein went to great lengths to prove that quantum mechanics was inconsistent, but Bohr always managed to refute the claims. But in his final attack, Einstein discovered something so profound, so controversial, so disturbing, and yet so predictable, that the topic has rekindled physicists’ interest at the start of the twenty-first century. Bohr’s only response to Einstein’s final discovery (the discovery of decay) was to ignore it.
The phenomenon of entanglement is an important aspect of quantum mechanics because it makes it indistinguishable from classical physics. It makes us wonder what we don’t understand about the reality of the world. The general opinion about physical systems is that if we know everything about the system—that is, everything that can be known—then we know everything about its parts. If we have full knowledge of the car’s features, we know everything about that at the highest level, from the wheels to the engine, from the transmission to the handling. It’s pointless for a mechanic to say, “I know everything about your car, but unfortunately, I can’t tell you anything about its parts.
“But this is exactly what Einstein explained to Bohr—in quantum mechanics, you can know everything about a system but nothing about its parts—but Bohr failed to realize this fact.” I should add that booksellers of this generation tend to overlook this fact.
Everyone is aware of the peculiarities of quantum mechanics, yet I believe that only a handful of individuals can accurately explain its workings. This book is a technical course on quantum mechanics, but it is less formal than most lectures or books. The focus is on sound principles, and the goal is not to hide quantum anomalies but to bring them to light.
I would like to remind you that this book is one of many sequels to my online course, Theoretical Minimum. My editor, Art Friedman, was in this class. The book benefits from being the subject of The Art of Learning and therefore pays close attention to topics that may confuse beginners. We thoroughly enjoyed the process of writing this and have endeavored to share some of these insights with you.
This spirit is infused with a touch of humor. If you can’t see it, ignore it. Leonard Susskind When I completed my master’s degree in computer science at Stanford, I could never have imagined that a few years later I would return and take Leonard’s physics class. My brief “career” in physics ended years ago when I received my degree. However, my interest in the subject remained strong.It seems that there are many people in the world who share my interest in facts and physics, but their lives lead them in different directions. This book is for all of us. We can partially attribute quantum mechanics to its qualitative nature. But it’s the numbers that bring the beauty of this into sharp focus. We have tried to make this beautiful work accessible to all illiterate people.I believe we have done a very good job, and I hope you agree..
No one could complete a project like this without a lot of help. The people at Brockman Inc. made the business look easy, and the team behind them at Perseus Books was top-notch. Special thanks to TJ Kelleher, Rachel King, and Tesse Takagi. We had the privilege of working with copywriting genius John Searcy. I am grateful to Leonard’s (other) continuing education students for consistently sparking thought-provoking and engaging discussions after class. Rob Colwell, Todd Craig, Monty Frost, and John Nash provided constructive comments on the manuscript. Jeremy Branscome and Russ Bryan reviewed the entire manuscript in detail and identified several problems. I am grateful to my family and friends for their support and enthusiasm. Special thanks to my daughter Hannah for helping me think about the store. In addition to her love, encouragement, insight, and humor, my wonderful wife, Margaret Sloan, provided nearly a third of Hilbert’s drawings and two paintings. Thank you, Maggie.
At the beginning of this project, Leonard, understanding my true motivation, told me that one of the best ways to learn physics was to write it down.Yes, it makes sense, but I wasn’t sure how true it was, and I’m glad I had the opportunity to find out. Thank you very much, Leonard. Art Friedman
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