The Gunners won 2-0 via goals from Ethan Nwaneri and Bukayo Saka.
"A beautiful evening for many reasons," Arteta said afterwards. "We are in the quarterfinals of the competition. We changed a lot of players today. We played players I never played before together against a very strong Premier League team.
"We had two debuts as a starter with Max (Dowman) and with Andre (Harriman-Annous) as well - I think everybody feels very, very proud of what they've done, the way they have responded to this huge challenge at their age and the fact that we won the game."
On playing Piero Hincapie and Cristhian Mosquera at the back, Arteta also said: "They'd never played together, so to build that chemistry, it takes time. I think they've done really, really well today. Again, for Piero especially, he hasn't played that many minutes to have his first start with the club.
"Again, a lot of positives to take, some very big learnings as well that we have to be very cautious of. But overall, a great night."