Philosophical Problems of Quantum Mechanics

Quantum mechanics refers to quantum systems and their environment. The theory does not include consciousness, human subjects, or detectors. The interaction of quantum systems with detectors is the subject of a different theory: quantum theory of measurement. Quantum systems have properties that are not classical. Sometimes they behave in a similar way to classical systems such as particles or waves, but they are neither of them. Other properties, such as spin, lepton number, or color, have no classical analogous. Entanglement is a property of quantum systems that are prepared in a certain state; this property holds as far as the system does not interact with other systems exchanging energy. Quantum mechanics is a realistic, non-local, deterministic, and probabilistic theory of microphysical objects. Its dynamical equations are lineal, and hence the state functions of quantum objects obey the Principle of Superposition. This results in a phenomenology that sometimes strongly differs from what we know from classical physics and common sense.