What is quantum physics?

Quantum physics explains the behavior of atoms, electrons and light. It provides experimentally testable probabilistic predictions where classical intuition fails. Its effects are not restricted to tiny particles: semiconductors, lasers and some large-scale states of matter also require quantum principles.

Fundamental quantum concepts

1. Quantization Some quantities in particular systems can take only discrete values, as with bound-electron energy levels in atoms. Not every quantity is discrete in every situation; free-particle energy can have a different mathematical structure. 2. Wave and particle properties Electron and photon experiments show interference patterns while detection produces individual events. Alternating between pictures of tiny balls and classical water waves does not give a complete explanation. Quantum theory calculates these outcomes in one framework. 3. Superposition A quantum state can be expressed as a combination of alternatives associated with a particular measurement. This does not mean an everyday object arbitrarily does everything at once. Possible outcomes and probabilities depend on how the physical system was prepared.

Measurement, entanglement and applications

4. Uncertainty Distributions of quantities such as position and momentum face a fundamental joint limit. This is not merely measurement error from poor instruments. Technical measurement limitations must be distinguished from basic properties of quantum states. 5. Entanglement The joint state of several particles may not be describable by assigning an independent state to each. Measurements can exhibit strong correlations. Entanglement alone does not transmit a chosen message faster than light; comparing results requires ordinary communication. 6. Technologies and misinterpretations Transistors and lasers successfully apply quantum physics. Quantum computing investigates controlled quantum systems. Calling a product quantum does not validate every claim: statements about health, consciousness or unlimited energy need their own testable evidence. Scientific findings should be distinguished from marketing metaphors.