It seems from @EmilioPisanty's comments on this question that the AC/optical Kerr effect is impractical for use in optical quantum computers, which leads me to ask: would the DC Kerr effect work?
The major difference between the optical/AC Kerr effect and the electro-optic/DC Kerr effect is that for the DC version to work, one must manually apply the electric field to the medium, whereas for the AC version, the light going through produces the effect itself.
In summary, is it possible to use a medium that exhibits the DC Kerr effect in place of a medium that exhibits the AC Kerr effect in an optical quantum computer?