The wish takes hold. "Very well. So it is spoken, so mote it be."
Magic flows, twists, inward to a tiny point, outward to the vast sky-
This is challenging. This is metamagic. He almost feels ill as he tries to guide it. It could go wrong so many ways. Make it something stable, a rock in an ocean, a hook to catch on the threads of divinity... But non-invasive, not something that pushes on Kaname Madoka, just something available.
The ribbon is, by far, the physical object with the greatest resonance. As a physical anchor for this magic, as an extant metaphor for Kaname Madoka, it reduces the metaphysical load considerably. He might as well make it nigh-indestructible while he's at it. (It glows slightly in Homura's hair.)
In a timeless and location-less place, as much as 'place' even means anything, an elegant spiral of magic opens up like a flower. A tunnel... No, a telephone line of sorts, from nowhere to a specific place and time. And a specific person- Homura Akemi.