Because of the way physics works, you'll never get 100% outcome, but there's work to show, that over a certain threshold, all errors can be corrected by the algorithm in a way, that the final result is 100% correct (threshold theorem, apparently errors up to 3% can be corrected in some settings). The end result is perfect, you just have to get there differently.

https://en.wikipedia.org/wiki/Quantum_error_correction

Disclosure: did my PhD (DPhil rather) in that group a while back (under Andrew Steane, he did research into error correction), awesome to see their work on HN, congrats all around! :)