I know they have a couple of small traders in the bond options on the floor of the CBOT. I know they have a few guys in the 10yr; not sure about the 5 and 30, though. When I say "small," I mean that they're not really big players in the market, like DRW, Knight, or Wolverine (which is bigger at CBOE, by the way). I think they make a handful of trades a day....their clerks don't do shit all day.
While QuietLight is definitely smaller than Knight, Wolverine, their size is actually only a little smaller to DRW (which isn't that big, really) and Peak6. They do mostly upstairs cross-margin stuff, so you won't see their floor guys do anything. QuietLight's founder (I forgot his name, but I have met him a couple of times) likes to be under the radar screen, but the amount of equity related stuff they do (SSF, etc), is very significant, far bigger than some of the other firms that have been asked here on ET.
QL is equity trading firm. Mr. Halston, who is the owner is a huge trader in S&P 500 options ath the CME. If you are interested in trading Fixed Income, you are barking up a wrong tree.
I do not know if he is still pit only, or if he is trading on screen, too. I have not been on the CME floor for at least 2.5 years. I know that he has screen traders trading equities, cash and futures