Quantum squeezing of vector slow-light solitons in a coherent atomic system

Abstract

We investigate the squeezing of two-component quantum optical solitons slowly moving in a tripod-type atomic system with double electromagnetically induced transparency (EIT). The evolution of the double probe-field envelopes is governed by a vector quantum nonlinear Schrödinger equation, derived from the coupled Heisenberg-Langevin and Maxwell equations. Quantum fluctuations of vector soliton pairs and atomic spin are analysed by means of a direct perturbation approach. Importantly, we find that the quantum squeezing of vector soliton pairs is generated by the giant Kerr nonlinearity, which is provided by EIT, and the outcome of the squeezing can be optimized by the selection of propagation distance and angle. The atomic spin squeezing is found for short propagation distances. The predicted results offer insights into soliton physics and may be useful for entanglement detection.