The energy of a substance when the temperature of that substance is absolute zero, or kelvin. Quantum theory says that a particle oscillating with simple harmonic motion does not have a state where the standard deviation of momentum is zero, and thus the kinetic energy in this case cannot be zero. Also, by the uncertainty principle, a confined particle must have at least (h-bar)^2/(2*m*L) where L is the dimension of the confinement, m is the particle's mass, and h-bar is Planck's constant over 2π.