What Is Entanglement and Why Is It Important?

SOLVED: A box containing a particle is divided into a right and a left compartment by a thin partition. If the particle is known to be on the right (left) side with certainty, the state is represented by the position eigenket |R⟩ (|L⟩), where we have neglected spatial variations within each half of the box. The most general state vector can then be written as |a⟩ = |R⟩⨂|aR⟩ |L⟩⨂|aL⟩, where |aR⟩ and |aL⟩ can be regarded as "wave functions." The particle can tunnel through

Quantum mechanics: Definitions, axioms, and key concepts of quantum physics

Quantum mechanics 101: Demystifying tough physics in 4 easy lessons