I'm not sure that has much at all to do with radiosity.
Well, basicly, the closer an object gets to a surface, the more light it blocks out within a certain area. What making a negative light on an object would do is simulate the blocking out of light it causes against other surfaces. For example, if you hold your hand close to a wall, you'll notice it the wall area right by your hand gets really dark, and since the farther away you something is the less light it blocks, using a linear drop-off negative light on something would have a similar effect (blocks out a lot of light when close, only blocks out a little when it's far away). It's sorta taking the "don't fix the dam, just waterproof your house" method of doing it, but I did test it out one time and it did look decent. Actually it does the opposite of radiosity: rather than tracing the actual light reflections, it would be an estimation of where the light WOULDN'T go. If HL2 or Doom 3 supports negative dynamic lights I'd actually like to try it out and see what the result is. Though it also might end up looking pretty crappy, depending on how it's implimented.
I'm not sure what's going on with quantum computers though. They certainly have potential, but they're so...different...that it would take a long time before we saw any practical consumer stuff out of it (it would work pretty good for things like encriptions and such though). Still, something to look forward to I guess, I just hope it doesn't put me out of a job