1. Superposition

A register of n qubits is described by 2ⁿ amplitudes. This gives quantum computing a large mathematical state space. However, measurement returns only one sampled bit string per run. Superposition is therefore a resource, not an automatic answer generator.

Superposition expands the space an algorithm can manipulate, but does not by itself create useful speedup.

2. Entanglement

Entanglement creates correlations among qubits that cannot be reproduced by assigning each qubit its own independent state. It is important for representing relationships in quantum systems, algorithms, communication, and error correction.

Entanglement does not transmit usable information faster than light.

Entanglement lets the computation represent joint structure that cannot be reduced to separate qubit descriptions.

3. Interference

Quantum amplitudes behave like waves: their phases can cause them to reinforce or cancel. Algorithms use gate sequences to increase the probability of useful outcomes and reduce the probability of unhelpful ones.

This is the most accurate intuitive explanation of quantum algorithmic power.

Quantum speedup comes from engineered interference, not from simply evaluating and reading all possibilities.

4. Applied activity

Draw two wave patterns: one in phase and one out of phase. Explain how the same principle becomes constructive and destructive interference in a quantum algorithm.