Quantum glossary

Spin

An intrinsic angular momentum of particles; for an electron, a two-level system that is a natural qubit.

Measuring spin along any axis gives only ±ħ/2, as Stern and Gerlach found in 1922. Nothing is literally spinning — the name is historical.

See it for yourself

Qubit — The basic unit of quantum information: a two-level system whose state is a normalised combination of |0⟩ and |1⟩.
Measurement — Reading out a qubit, which returns a classical bit sampled by the Born rule and leaves the qubit in the state matching it.