Have you ever thought of what a single photon looks like? In a multimode cavity it may be as simple as this.
Our paper titled Ultrafast Excitation Exchange in a Maxwell Fish-Eye Lens was published in Physical Review Letters. In the paper, we show that when placing two atoms in a very particular resonator - a Maxwell fish-eye lens - such a single photon pulse is emitted after exciting one of the atoms. The other atom can then after some time perfectly absorb this single photon, and send it back to the first atom. In short: It's like the two atoms were playing a game of ping-pong with a single photon as a ball.