He was referring to Palpatine's promise, and his new, yet to be found, powers...
PALPATINE: To cheat death is a power only one has achieved, but if we work together, I know we can discover the secret.
The masterstroke of Palpatine's plan was that he never even had to provide the goods (the actual power of immortality); he just had to make Anakin think they could find it. Combine that with Anakin's fear of losing Padme' from his vision/nightmare and his intense love for her, it was a hole in one.
I've actually realised an even greater irony; the quote in the OP from Anakin is "Love can't save you"... whereas it could've, and would've, saved her. If they'd not had their lava-fueled hissy fit and Anakin hadn't choked her into unconsciousness (which I'd not call very loving), they might've worked out their issues more 'lovingly' and moved on with their lives. Except that Anakin had, by that point, slaughtered most of the Jedi. But small steps.