Polarization squeezing of ultrashort pulses in fibres

We report on new experimental data and numerical simulations of quantum polarization squeezing in optical fibres. The experiment is a robust method for producing bright squeezed pulses of light. Because it can produce highly entangled states, the experiment operates in a very nonclassical regime, making the results sensitive to additional dissipative and thermal effects in the fibre. To characterize such experiments, we have performed quantum dynamical simulations of photonic pulses in a birefringent fibre, including all significant quantum effects and thermal noise. We use a novel experimental configuration combined with a detailed theoretical treatment that includes non-Markovian dissipative effects, to allow a quantitative comparison of experiment with quantum dynamical field theory simulations. The theory involves a first principles space-time evolution simulation of a many-body interacting quantum Bose gas, including dissipation. The high quality of the experimental data enables a comparison of simulation and experiment to well below the vacuum noise level, resulting in excellent agreement between theory and experiment over a wide range of pulse energies and fiber lengths. From the simulations, we identify the particular noise sources limiting the squeezing at high and low input energy.