# Why is HHL the popular choice to solve QLSP and not the Childs et al. (2017) algorithm?

The Childs et al. (2017) algorithm can solve the quantum linear systems problem (QLSP) in $$\operatorname{poly}(\log N, \log(1/\epsilon))$$ time while the HHL algorithm solves it in $$\operatorname{poly}(\log N, 1/\epsilon)$$ time. So, if the Childs algorithm is superior, then why is the HHL more popular?

Additionally, are there any examples of the Childs algorithm being used to solve a system of equations on a real or simulated quantum computer?

• I suppose only because HHL came earlier and is easier to understand? Mar 26 at 17:05
• Yea, that makes sense. I was just wondering if there is a technical reason for it. Mar 26 at 18:24