  We propose related schemes to generate arbitrarily shaped single photons,
i.e. photons with an arbitrary temporal profile, and coherent state
superpositions using simple optical elements. The first system consists of two
coupled cavities, a memory cavity and a shutter cavity, containing a second
order optical nonlinearity and electro-optic modulator (EOM) respectively.
Photodetection events of the shutter cavity output herald preparation of a
single photon in the memory cavity, which may be stored by immediately changing
the optical length of the shutter cavity with the EOM after detection.
On-demand readout of the photon, with arbitrary shaping, can be achieved
through modulation of the EOM. The second scheme consists of a memory cavity
with two outputs which are interfered, phase shifted, and measured. States that
closely approximate a coherent state superposition can be produced through
postselection for sequences of detection events, with more photon detection
events leading to a larger superposition. We furthermore demonstrate that
`No-Knowledge Feedback' can be easily implemented in this system and used to
preserve the superposition state, as well as provide an extra control mechanism
for state generation.
