➀ Quantum physicists have observed that photons can spend a negative amount of time in the excited state of atoms, seemingly exiting a material before entering it; ➁ The phenomenon was first proposed in 2017 and has now been experimentally confirmed; ➂ The researchers used a cloud of chilled atoms and found that sometimes photons pass through without exciting the atoms, yet the atoms still become excited; ➃ The results suggest that the photons moved through the medium faster when they excited the atoms than when the atoms remained in their ground state.