We haven't seen any sign of it. If we go to the open literature, Janes and the usual sort of information we get, we haven't seen that, but this doesn't necessarily mean that they haven't done it. Something like this can be developed very secretively.
Most of you will be aware, of course, that at one of the Chinese bases the submarines don't surface. There is a tunnel into the island where it's based. If they're developing this capability, they could have developed it without our knowing, and that's indeed a possibility.