Where Does the Quantum World End and Ours Begin?

Jonathan Halliwell explains how quantum decoherence is key to understanding how we transition from a world with a wave-like nature of matter and energy to the classical macroscopic world that we’re used to. The post Where Does the Quantum World End and Ours Begin? first appeared on Quanta Magazine

Résumé

Quantum mechanics basics

Quantum mechanics is a scientific framework that describes how particles and energy behave at very small scales, such as atoms and subatomic particles.

Unlike the predictable behavior of everyday objects, quantum systems exhibit unusual properties like wave-particle duality, where particles can act as both particles and waves.

For example, in the double-slit experiment, a single electron or photon can create an interference pattern as if it passed through both slits simultaneously, a phenomenon impossible for classical objects.

This was demonstrated even when only one particle was present in the experiment at a time, showing that quantum behavior is not dependent on large numbers of particles.

Quantum mechanics is the most precisely tested theory in science, with experiments confirming its predictions to an accuracy of one part in 10^12.

Despite its precision, there is no universally accepted interpretation of what quantum mechanics tells us about reality, making it one of the most debated topics in physics.