  Knill, Laflamme, and Milburn (KLM) proved that it is possible to build a
scalable universal quantum computer using only linear-optics elements and
conditional dynamics [Nature (London) {\bf 409}, 46 (2001)\cite{Knill}].
However, the practical realization of the quantum logic gate for the scheme is
still technically difficult. A major difficulty is the requirement for
sub-wavelength level stabilization of the interlocking interferometers.
Following our recent experimental work[Phys. Rev. Lett.{\bf 92}, 017902
(2004)\cite{Sanaka2}], we describe a more feasible scheme to implement the gate
that greatly reduces the experimental stability requirements. The scheme uses
only polarizing beam splitters and half-wave plates.
