In particular, feeding a photon pair into two input ports of a Mach–Zehnder interferometer yields a two-photon NOON state, thus producing double-density fringes 12.

potentially revolutionizing everything from quantum sensing to secure communication networks. Lee, D., et al. (2024) NOON-state interference in the frequency domain. Light: Science & Applications.

Now, researchers at the University of Toronto, through innovative quantum experiments ... putting them in a higher-energy or "excited" state before they return to normal. In research led by ...