[tellurion]

>Electromagnetic field oscillating over time is radiation: radio waves, light, x-rays, etc.

So they are red shifting or blue shifting the photons? And sending the red/blue shifted photons with a very small time delay?

[nine_k]

As far as I can understand the abstract (I did not shell out the $29), they register multiple red-shifted and blue-shifted photons, with their frequencies forming the expected stripe-like interference picture. They say: «The separation between time slits determines the period of oscillations in the frequency spectrum», that is, these "stripes" are not separated by space (red and blue circles) but rather by time. That is, the light quickly changes between red / blue shifted, as if we were traveling through the spatial interference picture, not looked at it "from above".

So yes, I think our understanding more or less matches: they likely register red/blue shifted photons with small time delays between the same "colors".