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 phrase quantum physics was first used in Johnston's Planck's Universe in Light of Modern Physics (1931). With decreasing temperature, the peak of the blackbody radiation curve shifts to longer wavelengths and also has lower intensities.