Uncertain Principles: The Real Point of Zero Point (and not The Point of The Zero Effect)

Zero-point energy is the energy associated with a particle in the lowest possible energy state. Since momentum is related to energy (for particles moving at speeds well below that of light, the kinetic energy of a moving particle is approximately one-half the momentum squared divided by the mass), low energy means low momentum, which means long wavelength. So if we want the lowest-energy state for a particle, we’re looking for the longest wavelength possible.

So what determines the longest wavelength possible?