  We propose an approach to optical quantum computation in which a
deterministic entangling quantum gate may be performed using, on average, a few
hundred coherently interacting optical elements (beamsplitters, phase shifters,
single photon sources, and photodetectors with feedforward). This scheme
combines ideas from the optical quantum computing proposal of Knill, Laflamme
and Milburn [Nature 409 (6816), 46 (2001)], and the abstract cluster-state
model of quantum computation proposed by Raussendorf and Briegel [Phys. Rev.
Lett. 86, 5188 (2001)].
