We propose a method to analyze the quantum correlations formed among the longitudinal modes of ultrafast laser pulses launched into an optical fiber and numerically demonstrate that parallel squeezed state generation can be achieved by a zero-dispersion fiber.
We propose a technique for generating momentum-squeezed states of optical pulses with a simple apparatus. An initial coherent state is launched into a dispersion-decreasing fiber, leading to pulse compression. The compressed pulse has a broader spectrum, but the average frequency of the pulse is fundamentally conserved by the Kerr effect. Although the momentum, or frequency, uncertainty of the pulse is not reduced, the final momentum uncertainty is below the coherent-state level with respect to the broadened output spectrum. The observable momentum uncertainty reflects photon correlations generated during the Kerr-effect scattering events. We discuss the basic characteristics of squeezing as well as the possibility of generating interesting quantum superposition states in an ideal lossless device.
We theoretically reveal the potential of the parallelism of squeezed state generation by nonlinear pulse propagation in an optical fiber. Starting from a nonlinear Schr\"odinger equation coupling with phonon modes that cause Raman noise, we develop a multimode quantum theory of nonlinear propagation in an optical fiber. Based on our proposed method, we numerically simulate fiber nonlinear propagation in two conditions: solitonlike and zero-group-delay-dispersion (zero-GVD) propagation. As a result, we find that zero-GVD propagation enables the large-scale parallel generation of squeezed states relative to solitonlike propagation owing to the broadband phase matching of the four-wave mixing process.
Bright squeezed light can be generated in optical fibers utilizing the Kerr effect for ultrashort laser pulses. However, pulse propagation in a fiber is subject to nonconservative effects that deteriorate the squeezing. Here, we analyze two-mode polarization squeezing, which is SU(2)-invariant, robust against technical perturbations, and can be generated in a polarization-maintaining fiber. We perform a rigorous numerical optimization of the process and the pulse parameters using our advanced model of quantum pulse evolution in the fiber that includes various nonconservative effects and real fiber data. Numerical results are consistent with experimental results.
Concepts and experimental works of ultrashort optical pulse squeezing in nonlinear fibers are reviewed. In a nonlinear fiber, optical fields are squeezed or quantum mechanically correlated by optical Kerr effect. These are, however, unobservable by direct photo-detection. Three kinds of strategies to extract the detectable squeezing have been proposed and implemented experimentally. Recent studies on applications of these squeezed pulses or the intrapulse quantum correlations to the generation of entangled states are also reviewed.