High-Effciency Cross-Phase Modulation in a Gas-Filled Waveguide    [PDF]

C. Perrella, P. S. Light, J. D. Anstie, F. Benabid, T. M. Stace, A. G. White, A. N. Luiten
Strong cross-Kerr non-linearities have been long sought after for quantum information applications. Recent work has shown that they are intrinsically unreliable in travelling wave configurations: cavity configurations avoid this, but require knowledge of both the non-linearity and the loss. Here we present a detailed systematic study of cross-phase modulation, and absorption, in a rubidium vapour confined within a hollow-core photonic crystal fibre. Using a two-photon transition, we observe phase modulations of up to $\pi$rad with a signal power of 25$\mu$W, corresponding to a non-linear Kerr coefficient, $n_2$, of $0.8 \times 10^{-6}$ cm$^2$/W, or $1.3 \times 10^{-6}$ rad per photon.
View original: http://arxiv.org/abs/1306.4396