Quantum optical synthesis of high-dimensional ultrafast frequency-bin qudits

TL;DR

This paper demonstrates engineering and characterization of high-dimensional frequency-bin entangled photon states, enabling scalable quantum information processing and communication over fiber networks.

Contribution

It introduces a method for generating and converting broadband frequency-entangled states into discrete, high-dimensional frequency bins with precise control and demonstrates their quantum nonlocality.

Findings

Achieved spectral anticorrelations over 38 frequency bins.

Bound on Hilbert-space dimensionality of at least 289.

Demonstrated quantum nonlocality over a fiber network.

Abstract

Frequency modes of light are one of the most promising platforms that provide access to high-dimensional quantum states amongst different photonic degrees of freedom capable of high-dimensionality, enabling robust, error-tolerant, and scalable quantum optical information systems. We demonstrate engineering of precisely controlled two-photon high-dimensional states entangled in frequency through time-domain Fourier optical synthesis. We generate and convert a continuous broadband frequency-entangled state into a large range of discrete frequency bins suitable for ITU standards, with spacings ranging from 12.5 GHz to 750 GHz, and observe spectral anticorrelations over 38 frequency bins, including intra-bin pure states at a 100 GHz bin spacing. We characterize the full quantum state dimensionality via Schmidt decomposition and observe lower bounds on the frequency-binned Hilbert-space dimensionalities of at least 289, formed by two entangled qudits with dimension 17. Furthermore, we demonstrate quantum nonlocality via frequency correlations in a transmission experiment over a campus-scale two-node fiber network. This work represents a crucial step towards building a versatile and relatively simple way of generating precisely controlled high-dimensional spectral qudits, with the potential of harnessing in wavelength-multiplexed quantum networks, high-dimensional information processing, and communication of quantum states specifically, and fiber-optic quantum remote sensing.