MIT Quantum Mechanics Lecture 1 - Spring 2013

Lecturer Introduction

• Lecturer: Allan Adams, Assistant Professor in Course 8, specializing in string theory, gravity, quantum gravity, and condensed matter physics.
• Course: Quantum Mechanics (804)
• Teaching Team: Recitation instructors Barton Zwiebach and Matt Evans, TA Paolo Glorioso.
• Video Recordings: Lectures are being videotaped for MIT OpenCourseWare.

Course Logistics

• Materials: Available on the Stellar website (lecture notes, homeworks, exams, grades).
• Problem Sets:
  • Due Tuesdays by 11 AM in the physics box.
  • No late work accepted; lowest problem set score will be dropped.
  • Collaboration encouraged, but write-ups must be individual.
• Exams: Two midterms and one final.
• Clickers: Required for participation and concept questions.
• Textbooks: No specific textbook chosen, recommendations available on Stellar.
• Office Hours: Encouraged as a place to ask questions.

Course Goals

• Learn Quantum Mechanics: Develop intuition for quantum phenomena beyond just calculations.
• Effort Requirement: Understand that quantum mechanics can be intuitive with effort.

Key Concepts Discussed

Quantum Mechanics and Experimentation

• Properties of Electrons: Introduced as having binary properties: color (black or white) and hardness (hard or soft).
• Measurement Devices:
  • Color Box: Measures electron's color, output as black or white.
  • Hardness Box: Measures electron's hardness, output as hard or soft.
• Repeatable Measurements: Once measured, electrons consistently show the same property when measured again with the same box.

Experimentation with Electrons

• Independence of Properties: Color and hardness of electrons are uncorrelated (e.g., knowing color does not predict hardness).
• Experiment Design:
  • Basic Experiment: Send electrons through series of color and hardness boxes to examine behavior.
  • Complex Experiment: Use mirrors to alter paths and analyze outcomes.

Key Observations

• Unpredictability and Randomness: Determining an electron’s output (color or hardness) shows inherent randomness.
• Impossibility of Combined Measurements: Cannot measure both color and hardness simultaneously with certainty.
• Uncertainty Principle: Some measurable properties of a system are incompatible, e.g., can't be both hard and white simultaneously.

Advanced Experimentation

• Apparatus with Hardness Box and Mirrors:
  • Designed to test the path taken by electrons.
  • Findings: Despite separations, electrons show behavior as if influenced by both paths without taking them distinctly.
• Superposition: New state of being where electrons aren’t just in a single measurable state.

Conclusion

• Quantum Mechanics Challenges Intuition: Recognizing electrons can be in a state of superposition is crucial.
• Course Objective: Develop intuition for quantum mechanics, transcending typical experience and logic.
• Next Steps: Dive deeper into the concept of superposition and quantum mechanics' foundational language.