Connect seam have square complexity

Hello, I have object A with object B,C,D into their private. I connect object A to B,C,D, B with C, B with D, and A with the exterior. For each A, I have one B,C,D.
I this case, the time of connexion/disconnection seam be square, Can you optimize that's to have linear complexity?
I my case, with 65535 object, the program use all of one core (then freeze into main thread).
I can be resolved into the new signals/slots system of Qt5? (Because it need architecture change)

Thanks.