  A fully optical method to perform any quantum computation with optical
waveguide modes is proposed by supplying the prescriptions for a universal set
of quantum gates. The proposal for quantum computation is based on implementing
a quantum bit with two normal modes of multi-mode waveguides. The proposed
universal set of gates has the potential of being more compact and easily
realized than other optical implementations, since it is based on planar
lightwave circuit technology and can be constructed by using Mach-Zehnder
interferometer configurations having semiconductor optical amplifiers with very
high refractive nonlinearity in their arms.
