How was Olivia powering the collision of the universes?

Question

In the season 4 finale, we find out that

William Bell is planning to let both universes collapse to create a new one of his design.

Since the Bridge has been deactivated, he has been using Olivia as a power source.

OLIVIA: The new energy source? It's me. Bell's going to try and use me to collapse the two universes. That's why he's been activating me.
_{Fringe, S4E22, "Brave New World, Part 2"}

Or perhaps that was his plan all along.

WILLIAM BELL: (...) Olivia is a living uncertainty engine. Every breath she takes brings us closer to Nirvana. Every beat of her heart tears the world from its hinges. She is The Redeemer. (...)

_{Fringe, S4E22, "Brave New World, Part 2"}

But how does this work? Is it merely Olivia's existence that does this? If the process somehow feeds of her energy, how?

Answer 1

They never go into much detail about how this works; the entire idea lasts only for the few scenes between us finding out about it and Peter stopping it. It's mostly just taken at face value that Bell knows what he's doing so whatever he says must be true, without much focus on how.

However, the implication that Olivia is somehow unique has to do with her history in the Cortexiphan program. Specifically, her special drug-induced power is the ability to jump between universes without any technological assistance. To my knowledge, she is the only character that was shown to possess this ability. Even when she was not planeswalking, she was able to detect objects that were in the wrong universe or were on the verge of crossing over.

On top of that, she was shown to be able to handle very large doses of the Cortexiphan, and Bell was able to reactivate the drug in her system years later.

All of that combines to give Olivia some kind of special connection to whatever mechanism bridges the two universes together. That, combined with all of the internal energy being created by the cortexiphan doses, somehow causes her to give off the right kind of power Bell needs.

(Yes, it's not a very satisfying answer. As @Andres says, this is one of many things that is explained in very vague, fuzzy terms.)