In
quantum mechanics, the
rectangular (or, at times,
square)
potential barrier is a standard one-dimensional problem that demonstrates the phenomena of
wave-mechanical tunneling (also called "quantum tunneling") and wave-mechanical reflection. The problem consists of solving the one-dimensional time-independent
Schrödinger equation for a particle encountering a rectangular
potential energy barrier. It is usually assumed, as here, that a
free particle impinges on the barrier from the left.