Qubits, Superposition & Entanglement

A classical bit is like a coin lying flat — heads (1) or tails (0). A qubit is like a coin spinning in the air — it's both simultaneously until you catch it (measure it). Mathematically, a qubit is in a state α|0⟩ + β|1⟩, where α and β are probability amplitudes. When measured, it collapses to 0 with probability |α|² or 1 with probability |β|². The power: with n qubits in superposition, you can represent 2ⁿ states simultaneously. 300 qubits can represent more states than there are atoms in the observable universe.

ENTANGLEMENT: Two qubits can be entangled — measuring one instantly determines the state of the other, regardless of distance. Einstein called this 'spooky action at a distance.' It's not faster-than-light communication, but it's a resource quantum computers exploit for coordinating computations. INTERFERENCE: Quantum algorithms work by setting up wave-like interference patterns. Correct answers amplify (constructive interference). Wrong answers cancel out (destructive interference). The art of quantum algorithm design is engineering these interference patterns to make the right answer more probable.