From quantum pulse gate to quantum pulse shaper—engineered frequency conversion in nonlinear optical waveguides

Abstract

Full control over the spatio-temporal structure of quantum states of light is\nan important goal in quantum optics, to generate for instance single-mode\nquantum pulses or to encode information on multiple modes, enhancing channel\ncapacities. Quantum light pulses feature an inherent, rich spectral\nbroadband-mode structure. In recent years, exploring the use of integrated\noptics as well as source-engineering has led to a deep understanding of the\npulse-mode structure of guided quantum states of light. In addition, several\ngroups have started to investigate the manipulation of quantum states by means\nof single-photon frequency conversion. In this paper we explore new routes\ntowards complete control of the inherent pulse-modes of ultrafast pulsed\nquantum states by employing specifically designed nonlinear waveguides with\nadapted dispersion properties. Starting from our recently proposed quantum\npulse gate (QPG) we further generalize the concept of spatio-spectral\nengineering for arbitrary $\\chitwo$-based quantum processes. We analyse the\nsum-frequency generation based QPG and introduce the difference-frequency\ngeneration based quantum pulse shaper (QPS). Together, these versatile and\nrobust integrated optics devices allow for arbitrary manipulations of the\npulse-mode structure of ultrafast pulsed quantum states. The QPG can be\nutilized to select an arbitrary pulse mode from a multimode input state,\nwhereas the QPS enables the generation of specific pulse modes from an input\nwavepacket with Gaussian-shaped spectrum.\n