  The present form of quantum mechanics is based on the Copenhagen school of
interpretation. Einstein did not belong to the Copenhagen school, because he
did not believe in probabilistic interpretation of fundamental physical laws.
This is the reason why we are still debating whether there is a more
deterministic theory. One cause of this separation between Einstein and the
Copenhagen school could have been that the Copenhagen physicists thoroughly
ignored Einstein's main concern: the principle of relativity. Paul A. M. Dirac
was the first one to realize this problem. Indeed, from 1927 to 1963, Paul A.
M. Dirac published at least four papers to study the problem of making the
uncertainty relation consistent with Einstein's Lorentz covariance. It is
interesting to combine those papers by Dirac to make the uncertainty relation
consistent with relativity. It is shown that the mathematics of two coupled
oscillators enables us to carry out this job. We are then led to the question
of whether the concept of localized probability distribution is consistent with
Lorentz covariance.
