These subjects are complementary. There are many jobs that would make use of skill sets from more than one of the majors you're considering. A combination of physics, math, and computer science would also serve as excellent preparation for a graduate degree in any of those three subjects. For example, one might attempt writing code that implements equations from physics to analyze empirical data. A strong math background combined with computer science would open up subjects like cryptography, error correction, data compression, computer graphics, or scientific computation.
