  We show that the transfer of the angular spectrum of the pump beam to the
two-photon state in spontaneous parametric down-conversion enables the
generation of entangled Hermite-Gaussian modes. We derive an analytical
expression for the two-photon state in terms of these modes and show that there
are restrictions on both the parity and order of the down-converted
Hermite-Gaussian fields. Using these results, we show that the two-photon state
is indeed entangled in Hermite-Gaussian modes. We propose experimental methods
of creating maximally-entangled Bell states and non-maximally entangled pure
states of first order Hermite-Gaussian modes.
