13. Quantum superposition

📘 Lesson 13 of 21

▶️ Watch the full lecture series here:    • Quantum Mechanics: Elementary Concepts  

Can a particle be in two states at once?

In this lesson, you'll discover the principle of quantum superposition—the idea that a quantum system can exist in a combination of multiple states at the same time. We show how wave functions can be added together to form new, valid quantum states, and prove that these superpositions still satisfy the Schrödinger equation. As a striking example, we construct a "cat state" from two spatially separated coherent states of a harmonic oscillator, illustrating how quantum systems can embody classically contradictory properties—like being on the left and right at once.

📝 Solved exercises for this course are available here: https://www.quantphys.com/lessons/qm1