Physical Review Letters ( IF 8.385 ) Pub Date :
Steven Sagona-Stophel; Reihaneh Shahrokhshahi; Bertus Jordaan; Mehdi Namazi; Eden Figueroa

The development of useful photon-photon interactions can trigger numerous breakthroughs in quantum information science, however this has remained a considerable challenge spanning several decades. Here we demonstrate the first room-temperature implementation of large phase shifts ($\approx \pi$) on a single-photon level probe pulse (1.5us) triggered by a simultaneously-propagating few-photon-level signal field. This process is mediated by $R{b}^{87}$ vapor in a double-$\Lambda$ atomic configuration. We use homodyne tomography to obtain the quadrature statistics of the phase-shifted quantum fields and perform maximum-likelihood estimation to reconstruct their quantum state in the Fock state basis. For the probe field, we have observed input-output fidelities higher than 90$%$ for phase-shifted output states, and high overlap (over 90%) with a theoretically perfect coherent state. Our noise-free, four-wave-mixing-mediated photon-photon interface is a key milestone towards developing quantum logic and non-demolition photon detection using schemes such as coherent photon conversion.

down
wechat
bug