Bad Qubits — Learn Quantum by Doing

Multiple choice

In Gamow's model of alpha decay, an alpha particle with energy of a few MeV escapes a nucleus even though the Coulomb barrier peak is tens of MeV. By what mechanism does it escape, and how does the escape probability behave?

The barrier instantly vanishes whenever the alpha particle approaches the nuclear surface
Quantum tunneling through the Coulomb barrier, with transmission probability $T \sim e^{-2G}$ ( $G$ the Gamow factor)
Classical over-barrier escape once thermal fluctuations push its energy above the barrier peak
It absorbs energy from the uncertainty principle to momentarily exceed the barrier height