  The quantum state of an electron in a strong laser field is altered if the
interaction of the electron with its own electromagnetic field is taken into
account. Starting from the Schwinger-Dirac equation, we determine the states of
an electron in a plane-wave field with inclusion, at leading order, of its
electromagnetic self-interaction. On the one hand, the electron states show a
pure "quantum" contribution to the electron quasi-momentum, conceptually
different from the conventional "classical" one arising from the quiver motion
of the electron. On the other hand, the electron self-interaction induces a
distinct dynamics of the electron spin, whose effects are shown to be
measurable in principle with available technology.
