  30$^{\circ}$ twisted bilayer graphene demonstrates the quasicrystalline
electronic states with 12-fold symmetry. These states are however far away from
the Fermi level, which makes conventional Dirac fermion behavior dominating the
low energy spectrum in this system. By using tight-binding approximation, we
study the effect of external pressure and electric field on the
quasicrystalline electronic states. Our results show that by applying the
pressure perpendicular to graphene plane one can push the quasicrystalline
electronic states towards the Fermi level. Then, the electron or hole doping of
the order of $\sim$ $4\times10^{14}$ $cm^{-2}$ is sufficient for the
coincidence of the Fermi level with these quasicrystalline states. Moreover,
our study indicates that applying the electric field perpendicular to the
graphene plane can destroy the 12-fold symmetry of these states and break the
energy degeneracy of the 12-wave states, and it is easier to reach this in the
conduction band than in the valence band. Importantly, the application of the
pressure can recover the 12-fold symmetry of these states to some extent
against the electric field. We propose a hybridization picture which can
explain all these phenomena.
