  We consider quantum error-correction codes for multimode bosonic systems,
such as optical fields, that are affected by amplitude damping. Such a process
is a generalization of an erasure channel. We demonstrate that the most
accessible method of transforming optical systems with the help of passive
linear networks has limited usefulness in preparing and manipulating such
codes. These limitations stem directly from the recoverability condition for
one-photon loss. We introduce a three-photon code protecting against the first
order of amplitude damping, i.e. a single photon loss, and discuss its
preparation using linear optics with single-photon sources and conditional
detection. Quantum state and process tomography in the code subspace can be
implemented using passive linear optics and photon counting. An experimental
proof-of-principle demonstration of elements of the proposed quantum error
correction scheme for a one-photon erasure lies well within present
technological capabilites.
