I'm reading the paper Implementation of the Quantum Fourier Transform. On page 4, they write
To a first approximation, decoherence during the course of the QFT attenuates the entire density matrix. This is shown in figure 2.
I know that the word "attenuate" means to dampen or reduce the force of something. Since density operators have trace one, perhaps this means that the QFT decreases the trace of the density operator...
My questions are
- What is meant by attenuate here?
- Why does decoherence during the course of the QFT do this, and why "to a first approximation"?