The generation of light in specific quantum states, particularly controlling the photon number, is crucial for advancing optical quantum technologies. We successfully generated quantum superpositions of zero, one, and two photons through pulsed coherent control of a single artificial atom. This process involves driving the system to full atomic inversion to create superpositions of vacuum and one photon, with their populations finely tuned by the intensity of the driving laser. Further intensification with 2π-pulses led to a coherent superposition that includes a two-photon component surpassing the one-photon term, facilitating advanced applications like phase super-resolving interferometry. This breakthrough demonstrates a significant step forward in utilizing the photon-number degree of freedom, offering new possibilities for optical quantum technologies.

Reference:

• J. C. Loredo et al. (2019). “Generation of non-classical light in a photon-number superposition,” Nature Photonics, 13(11), 803–808.