In sensus plenior darkness is Love as expressed in unity, grace, mercy, long-suffering, patience, etc. and Light is Holiness, as expressed in separation, law, justice, judgement, patience etc.
The Trinity existed in darkness/love before creation, but the Light/holiness was hidden in God, as expressed in the pun for Elohim (alo khoom - meaning 'not dark'). The Light, or the revelation of God as Holiness did not exist because there was nothing for him to be separate from. As soon as there was a creation, holiness could be expressed.
Light, as a metaphor for holiness, was pre-existent, but hidden in God himself.
God's revelation of himself is given in two paths Holiness and Love. When we understand them individually, He reconciles them on the cross. What was parted at creation is joined at the cross.
From a physics point of view: Experiments concerning "Shrodinger's cat" basically create light in opposite phases from nothing. Since the law of conservation of energy is not violated, quantum leaps of information can be created. Light and 'anti-light' are separated from nothingness.
This article shows one implementation using entangled particles. Another implementation in Australia accomplishes it within a light tube where the energy pattern put in one end exists the other simultaneously by splitting off an energy pattern traveling in reverse through the tube, originating at the exit face.
At the exit face, the two expressions of the pattern are created out of 'nothing' and express the input pattern in two ways. If people could actually understand what is going on it would be a great picture of splitting two expressions of God's revelation of himself out of nothing at His command.