For 10 points, name this state which describes space, which is completely devoid of matter.
The QED type of this entity approaches the classical type as Planck's constant approaches zero. The characteristic impedance of this entity is equal to three hundred seventy seven ohms. Zero point energy describes the energy in this entity, for which the D and H fields simplify to E and B fields, respectively. Attempts to create these entities have only been successful at getting to below ten to the minus nine torr. The index of refraction is defined as the ratio of the speed of light in this entity to the speed of light in a particular medium. For 10 points, name this state which describes space, which is completely devoid of matter.
The QED type of this entity approaches the classical type as Planck's constant approaches zero.
{Vacuum}