  We put forward an interpretation of scalar quantum field theory as
relativistic quantum mechanics by curing well known problems related to
locality. A probabilistic interpretation of quantum field theory similar to
quantum mechanics is difficult if particle localization is defined using the
Newton-Wigner position operator as it is non-local and non-covariant. An
alternative bilinear covariant position operator is discussed which
incorporates a time operator that can be exponentiated to a unitary operator.
Moreover, it satisfies an algebra that unifies special relativity and quantum
mechanics and has the same form for particles with spin. Higher power position
operators are derived which yield Heisenberg's uncertainty relations. Our ideas
are illustrated with a relativistic wave function whose probability density can
be perfectly localized.
