Lecture Notes: Introduction to Quantum Mechanics (Course 804, Spring 2013)
Introduction
Lecturer: Allan Adams, Assistant Professor in Course 8 (string theory, gravity, quantum gravity, condensed matter physics)
Recitation Instructors: Barton Zwiebach, Matt Evans (new faculty), TA: Paolo Glorioso
Course objective: Develop an intuition for quantum mechanics rather than just calculations.
Quantum Mechanics: Reputably hard, but everyone can learn it with effort.
Course Organization
Materials: Everything will be available on the Stellar website (lecture notes, homeworks, exams, grades).
Workload: Problem sets due weekly on Tuesdays by 11 AM; one lowest score will be dropped.
Collaboration: Encouraged on problem sets but must write them up individually.
Assessment: Two midterms, one final exam, and participation via clickers.
Textbooks: No specific textbook assigned; a list of recommended texts provided. Different books may focus on wave mechanics or matrix mechanics.
Learning Quantum Mechanics
Quantum phenomena require problem-solving to develop intuition.
Ask questions; there are no bad questions.
First Thought Experiments
Experiments involving electrons to explore properties:
Color (binary: black or white)
Hardness (binary: hard or soft)
Key Experimental Setup
Create devices (color and hardness boxes) that measure these properties.
Every measurement yields persistent properties: once measured, they retain their classification (i.e., once black, always black).
Correlation Experiments
Investigate if color and hardness are related or correlated properties:
Randomly sample electrons and send them through measurement boxes.
Results show independence: knowing color does not predict hardness and vice versa.
Surprising Results
Even when measurements induce expectations (100% white from a white source), sending selected electrons through additional boxes yields unexpected distributions (50% outcomes).
Important conclusion: Electrons do not exist in a clear state until measured (superposition).
Superposition and Measurement
Superposition: Electrons can be in multiple states simultaneously.
Rethink intuition about particle behavior and measurement: it does not conform to classical expectations.
There is a randomness inherent in quantum mechanical behavior, challenging classical views of determinism.
Conclusion of Lecture
The goal of the course is to reframe intuition away from classical physics towards quantum mechanics.
Future lectures will build on these principles and explore superposition in greater depth.