  The generation and detection of maximally-entangled two-particle states,
`Bell states,' are crucial tasks in many quantum information protocols such as
cryptography and teleportation. Unfortunately, they require strong
inter-particle interactions lacking in optics. For this reason, it has not
previously been possible to perform complete Bell state determination in
optical systems. In this work, we show how a recently developed quantum
interference technique for enhancing optical nonlinearities can make efficient
Bell-state measurement possible. We also discuss weaknesses of the scheme
including why it cannot be used for unconditional quantum teleportation.
