Title: "A global view of quantum computation with noisy components"

Abstract:
Quantum computers are physical devices which, if they can be built, 
would allow to manipulate a global quantum state to accomplish some 
computational task. A main experimental challenge is how to keep the 
state isolated from the surrounding world so that it remains quantum, 
and does not turn classical. This challenge comes with the theoretical 
problem of estimating the errors made by a quantum computer which is 
not perfectly isolated from the environment. In the quantum computing 
literature this has mainly been addressed in a factorized model introduced 
by Aharonov, Kitaev and Nisan in 1998.

In this talk I will describe how to estimate the errors general quantum 
computation by the Feynman-Vernon method, hence by-passing the assumptions 
in the Aharonov-Kitaev-Nisan theory. I will show how some simple estimates 
can be obtained for idealized systems, and how they can also be extended 
for more advanced schemes such as Kitaev's toric code. I will also 
discuss quantum error correction and error protection in such systems.

The talk is mainly based on arXiv:1606.09407.