Room temperature conditional $\pi$-phase shifts mediated by simultaneously propagating single-photon level pulses
Reihaneh Shahrokhshahi, Steven Sagona-Stophel, Bertus Jordaan, Mehdi Namazi, Eden V. Figueroa · arXiv (Cornell University) · 2018
Here we demonstrate the first room-temperature implementation of $\pi$ phase shifts in single-photon-level probe light created by a simultaneously propagating few-photon triggering signal field. The photon-photon interaction is mediated by rubidium atoms in a double $\Lambda$ atomic scheme. We use homodyne tomography and maximum likelihood estimation on the quadrature statistics of the input and phase-shifted photons to fully characterize their quantum states in the Fock state basis. For particular choices in control fields strengths and input phases, the input-output fidelity of the controlled $\pi$ phase shift operation reaches $\sim$90$\%$.