A Programmable Spatiotemporal Quantum Parametric Mode Sorter

TL;DR

This paper presents an experimental demonstration of a programmable quantum mode sorter capable of high-dimensional spatiotemporal signal separation using mode-selective frequency up-conversion, enhancing quantum communication capabilities.

Contribution

It introduces a novel, fully programmable quantum mode sorter for high-dimensional spatiotemporal signals using mode-selective frequency up-conversion, with optimized performance for quantum applications.

Findings

Achieved over 12 dB extinction in mode sorting.

Improved performance by coupling into single-mode fiber.

Demonstrated faithful mode and superposition mode selection.

Abstract

We experimentally demonstrate a programmable parametric mode sorter of high-dimensional signals in a composite spatiotemporal Hilbert space through mode-selective quantum frequency up-conversion. As a concrete example and with quantum communication applications in mind, we consider the Laguerre-Gaussian and Hermite-Gaussian modes as the spatial and temporal state basis for the signals, respectively. By modulating the spatiotemporal profiles of the up-conversion pump, we demonstrate the faithful selection of single photons in those modes and their superposition modes. Our results show an improvement in the quantum mode-sorting performance by coupling the up-converted light into a single-mode fiber and/or operating the upconversion at the edge of phase matching. By optimizing pump temporal profiles only, we achieve more than 12 dB extinction for mutually unbiased basis (MUB) sets of the spatiotemporal modes. This fully programmable and efficient system could serve as a viable resource for quantum communications, quantum computation, and quantum metrology.