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.
The word quantum means a definite but small amount. The basic quantum constant h, known as Planck's constant,and its value is 6.626 x 10-34 Js The quantum theory of physics was developed in order to explain the relationship between matter and energy at an atomic level as well as subatomic.