Quantum fluctuations are small variances in matter due to Heisenberg's uncertainty principle. This states that the more we know about where a particle is, the less we know about where it is going. Basically, small amounts of energy may change, and this is accepted in the scientific community.
Quantum fluctuations can result in theoretical photons being created from nothing. These photons have no actual energy value. Like all photons, these theoretical photons can split into an electron and a positron. However, normal photons must interact with matter for this to occur, whereas theoretical photons do not. Like normal matter and antimatter, this theoretical electron and positron annihilate each other. Unlike normal matter, however, they do not create any energy when they annihilate each other, but instead create an imaginary photon.