  We present a broad family of quantum baker maps that generalize the proposal
of Schack and Caves to any even Hilbert space with arbitrary boundary
conditions. We identify a structure, common to all maps consisting of a simple
kernel perturbed by diffraction effects. This "essential" baker's map has a
different semiclassical limit and can be diagonalized analytically for Hilbert
spaces spanned by qubits. In all cases this kernel provides an accurate
approximation to the spectral properties - eigenvalues and eigenfunctions - of
all the different quantizations.
