Is it experimentally validated that virtual photons exists? 

If they have mathematical significance it should have physical significance as well.

I guess we don't have the ability now to understand or directly observe them as of now. 

@Bhushan: A similar doubt may arise considering whether or not the waves advanced in the electromagnetic interaction exist (and this problem is not only reported as an example: it is very deep). We eliminate the advanced wave sic et simpliciter saying it is a Junk solution reported (unfortunately) by mathematics. The trick is to understand why mathematics has something that you do not need (repeating your words).... or better: understanding the meaning of math does imply a correct description of phenomena?

@V. Fulcoli  Yes I agree with you, according my latest paper I get E=mc2+ihv for matter (see attachment).

I am wondering if this is related to virtual photons or not (I have associated it with matter waves). But not sure what roles it plays in virtual photons. 

Thesis Energy equation in complex plane

Thanks S.K. Bose