With the release of the G80, NVIDIA will also release a new engine dubbed Quantum physics engine.  Quantum Effects Technology is similar (at least in spirit) to NVIDIA's PureVideo Technology -- a dedicated layer on the GPU for physics calculations.  A few documents alluding to this new engine appeared on public FTP mirrors late last week.

Quantum utilizes some of the shaders from NVIDIA's G80 processor specifically for physics calculations.  Physics calculations on GPUs are nothing new; ATI totes similar technology for its Stream Computing initiative and for the Triple Play physics. 

NVIDIA and Havok partnered up this year claiming that SLI systems would get massive performance gains by utilizing additional GeForce GPUs as physics processors.  Quantum may be the fruits of that partnership, though NVIDIA documentation clearly states that Quantum will work just fine without SLI.

NVIDIA's documentation claims Quantum will specifically compete with AGEIA's PhysX, yet does not mention who is providing the middleware.  Given that there are only two acts in town right now, it would be safe to say Havok has a hand in the Quantum engine.