Quantum Mechanics
The physics of the very small — where particles behave like waves, outcomes are probabilistic rather than certain, and measurement itself changes what is measured. Built from Planck's 1900 quantum hypothesis through Schrödinger, Heisenberg, and Dirac's formalisms of the 1920s.
Quantum mechanics is the branch of physics describing the behaviour of matter and energy at atomic and subatomic scales, where classical certainty is replaced by probability amplitudes, physical quantities are quantised into discrete values, and systems can exist in superpositions of multiple states until measured.
What this domain covers
Quantum mechanics answers questions classical physics cannot: why do atoms not collapse as orbiting electrons radiate away energy? Why does light sometimes behave as a particle and sometimes as a wave? Why can a measurement on one particle instantaneously correlate with a measurement on another, arbitrarily far away? This domain covers the foundational experiments and principles (wave-particle duality, the uncertainty principle, superposition), the Schrödinger equation and its solutions for standard systems, the operator formalism that makes quantum mechanics mathematically precise, angular momentum and spin, the hydrogen atom, the physics of identical particles, approximation methods for problems with no exact solution, and the long-running debate over what quantum mechanics means at a foundational level — entanglement, Bell's theorem, and the competing interpretations.
Foundations
- Wave-Particle Duality [DONE — Session 04 — 2026-07-06]
- Photoelectric Effect [PENDING FULL ENTRY]
- De Broglie Hypothesis [PENDING FULL ENTRY]
- Double-Slit Experiment [PENDING FULL ENTRY]
- Uncertainty Principle [DONE — Session 04 — 2026-07-06]
- Wave Function [DONE — Session 04 — 2026-07-06]
- Born Interpretation [DONE — Session 04 — 2026-07-06]
- Quantum Superposition [DONE — Session 04 — 2026-07-06]
- Quantum Measurement [PENDING FULL ENTRY]
Schrödinger Equation
- Schrödinger Equation (concept entry) [PENDING FULL ENTRY — see equation page, already live]
- Time-Dependent Form [PENDING FULL ENTRY]
- Time-Independent Form [PENDING FULL ENTRY]
- Particle in a Box [PENDING FULL ENTRY]
- Quantum Harmonic Oscillator [PENDING FULL ENTRY]
- Finite Potential Well [PENDING FULL ENTRY]
- Quantum Tunnelling [PENDING FULL ENTRY]
Operators & Formalism
- Operators in Quantum Mechanics [PENDING FULL ENTRY]
- Observables [PENDING FULL ENTRY]
- Eigenvalues & Eigenvectors [PENDING FULL ENTRY]
- Dirac Notation [PENDING FULL ENTRY]
- Hilbert Space [PENDING FULL ENTRY]
- Commutator [PENDING FULL ENTRY]
- Hermitian Operators [PENDING FULL ENTRY]
Angular Momentum & Spin
- Orbital Angular Momentum [PENDING FULL ENTRY]
- Spin [PENDING FULL ENTRY]
- Spin-½ [PENDING FULL ENTRY]
- Pauli Matrices [PENDING FULL ENTRY]
- Addition of Angular Momenta [PENDING FULL ENTRY]
- Clebsch-Gordan Coefficients [PENDING FULL ENTRY]
Hydrogen Atom & Atomic Structure
- Hydrogen Atom [PENDING FULL ENTRY]
- Quantum Numbers [PENDING FULL ENTRY]
- Atomic Orbitals [PENDING FULL ENTRY]
- Zeeman Effect [PENDING FULL ENTRY]
- Stark Effect [PENDING FULL ENTRY]
- Spin-Orbit Coupling [PENDING FULL ENTRY]
Identical Particles
- Identical Particles [PENDING FULL ENTRY]
- Pauli Exclusion Principle [PENDING FULL ENTRY]
- Fermions & Bosons [PENDING FULL ENTRY]
- Slater Determinant [PENDING FULL ENTRY]
Approximation Methods
- Perturbation Theory [PENDING FULL ENTRY]
- Time-Independent Perturbation Theory [PENDING FULL ENTRY]
- Time-Dependent Perturbation Theory [PENDING FULL ENTRY]
- Variational Method [PENDING FULL ENTRY]
- WKB Approximation [PENDING FULL ENTRY]
Entanglement & Interpretations
- Quantum Entanglement [PENDING FULL ENTRY]
- Bell's Theorem [PENDING FULL ENTRY]
- EPR Paradox [PENDING FULL ENTRY]
- Copenhagen Interpretation [PENDING FULL ENTRY]
- Many-Worlds Interpretation [PENDING FULL ENTRY]
- Pilot-Wave Theory [PENDING FULL ENTRY]
- Decoherence [PENDING FULL ENTRY]
Sources
- Griffiths, D.J., Schroeter, D.F. (2018). Introduction to Quantum Mechanics, 3rd ed. Cambridge University Press.
- Sakurai, J.J., Napolitano, J. (2020). Modern Quantum Mechanics, 3rd ed. Cambridge University Press.