quantum mechanics

The fundamental theory of physics describing nature at the scale of atoms and subatomic particles.

• state of a system encoded in a wave function (Schrodinger equation)
• superposition: systems exist in multiple states simultaneously until measurement
• entanglement: correlated states across spacetime, foundational for quantum information theory
• measurement collapses the wave function — outcome is probabilistic
• Planck constant sets the scale separating quantum from classical mechanics
• energy, momentum, and angular momentum are quantized
• underpins electromagnetism (quantum electrodynamics), chemistry, and computation
• field theory extends quantum mechanics to relativistic domains — see relativity