Quantum tunneling decay due to interference of a bound and an antibound state

We consider an exact analytical formulation of the wave function for quantum tunneling decay, given as an expansion in terms of the bound, antibound, and resonant states, for the time-honored problem of a particle initially confined by a potential. We find that the interference term between a bound state and its corresponding antibound state may favor a decay process in which the probability density spreads throughout space in a nonexponential fashion.