Creation of Photon States with Negative Wigner Function with Tunable N-Level EIT Processes

Strong optical nonlinearities are key to a range of optical technologies, in particular, to the generation of quantum light states. This paper proposes and demonstrates a novel nonlinear mechanism based on an N-level electro-magnetic induced transparency (EIT) in a warm rubidium vapor. Our scheme relies on using an optical frequency comb as a pump and a CW probe signal, which co-propagate and interact in warm rubidium vapor, as shown in Fig. 1(a). Multiple comb lines excite N-level EIT resonances as shown in Fig. 1(b), which modifies the optical response of the medium, creating a giant Kerr nonlinearity [1], which opens the way for different phenomena like slow light propagation or generation of quantum light states. Here, we experimentally create the giant Kerr nonlinearity, with the magnitude ranging from 1.2 x 10–<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> to 7.7 × 10–<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>V<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup>.