From https://developer.apple.com/arkit/:
ARKit runs on the Apple A9, A10, and A11 processors.
From https://www.apple.com/iphone-se/specs/:
A9 chip with 64‑bit architecture.
But from the iOS Device Compatibility Reference:
This says that iPhone SE is not compatible with ARKit. Could anybody clarify this for me?
Update: Apple updated the table. Now iPhone SE is showing as compatible with ARKit.