Quantum mechanics is the branch of physics that studies the behavior of matter and energy in the presence of an observer. It is the foundation of modern physics and the theory of the wave-particle duality.
In quantum mechanics, an object can exist in more than one state simultaneously. This means that it can be in two or more places at the same time, or have two or more different properties such as spin or momentum. The behavior of a quantum object is determined by its wave function, which describes all possible states that it can occupy.
The wave function of a quantum object is governed by the Schrödinger equation, which is a differential equation that determines how the wave function changes over time. The solution to this equation gives rise to the famous Heisenberg uncertainty principle, which states that certain pairs of physical quantities (such as position and momentum) cannot both be known with absolute precision.
Quantum mechanics has been extraordinarily successful in explaining the behavior of matter and energy on atomic and subatomic scales. Its predictions have been verified experimentally to an extremely high degree of accuracy. Quantum mechanics also forms the basis for our understanding of many phenomena that are otherwise inexplicable, such as superconductivity and quantum entanglement.