Sometimes, there is an absolute limit on the number of terms an officeholder can serve, while, in other cases, the restrictions are merely on the number of consecutive terms.
For example, Maxwell's Equations would always be capitalized, while quantum mechanics is usually un-capitalized. I searched half a dozen sites for an answer to this but found no clue about a rule. So go either way that makes you happy, but (most of all) be consistent.
Related to quantum physics: quantum theory. n. (used with a sing. verb) The branch of physics that uses quantum theory to describe and predict the properties of a physical system. Also called quantum mechanics. The branch of physics that uses quantum theory to describe and predict the properties of a physical system.