Optical quantum frequency standard bases for MADQuantum-CM communication network
Ismael Caballero, Adriana Palos, Daniel de Mecado, Yolanda Álvarez, David Peral, Javier Díaz de Aguilar · 2025
This paper presents the development of an optical frequency standard based on trapped ions within the MADQuantum-CM project, aimed at establishing a quantum communications network in the Community of Madrid. Centro Español de Metrología (CEM) has a key role as a node in this network, contributing to its synchronization through a high-precision frequency reference.The optical frequency standard developed at CEM utilizes the 4 S1/2↔ 3 D5/2transition in40Ca+ions at 729 nm. This system comprises an ion trapping setup using a Paul trap, laser cooling techniques, and an ultra-stable laser to achieve a linewidth in the order of 1 Hz. Additionally, a frequency comb is employed to ensure precise optical frequency measurements.By integrating this frequency standard into the quantum network, highly stable and accurate time references will be able to be distributed, which is essential for quantum communication protocols.