Chop and change The top panel shows a photon (represented as a wave) being reflected from a mirror. The wave is incident from left to right with the solid blue line showing the portion of the wave travelling left to right and the dashed line showing the portion of the wave that has been reflected back to the left. The researchers considered what happens when the mirror is removed and the truncated wave continues to travel to the right. The lower panel shows the situation shortly after the mirror has been removed. The narrow central portion is the complicated transition region containing multiple photons. The region to the left shows a truncated photon state that is locally equivalent to a single photon. To the right is the truncated photon shown as locally equivalent to the vacuum state. (Courtesy: Isak Cecil Onsager Rukan, Jan Gulla, Johannes Skaar/ Phys. Rev. Lett.…