High-Effciency Cross-Phase Modulation in a Gas-Filled Waveguide

TL;DR

This paper demonstrates highly efficient cross-phase modulation using rubidium vapor in a hollow-core photonic crystal fiber, achieving significant phase shifts at low power levels suitable for quantum information processing.

Contribution

It provides a systematic study of cross-phase modulation in a gas-filled waveguide, achieving high non-linear Kerr coefficients and phase shifts with low signal power, advancing quantum nonlinear optics.

Findings

Phase modulation of up to π radians at 25 μW signal power.

Non-linear Kerr coefficient of 0.8 × 10^{-6} cm^2/W.

Phase shift of 1.3 × 10^{-6} radians per photon.

Abstract

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.