23 August 2018 Quantum Storages on Optica cover

Cover of Optica - 2018 August Issue

An ICFO and IFN-CNR study on quantum storage makes it to the cover of OSA’s Optica August 2018 issue. Photonic quantum memories are a key ingredient for quantum information science, in particular for the development of quantum networks. Solid-state quantum storage devices based on rare-earth-ion-doped crystals present appealing properties for quantum storage of light, presenting long coherence times and prospects for integration, which are essential in the advancement of scalable quantum information technologies.

Combining solid-state quantum storage devices with guided wave optics offers several advantages, such as compactness, scalability, efficiency due to enhanced light–matter interaction, and improved mechanical stability. These devices can be connected with other integrated quantum devices, such as single-photon sources, photonic circuits, and detectors, which enables them to be integrated into complex quantum architectures. Also, the compatibility of waveguide-based devices with fiber optics would enable interconnection between quantum memories and the current fiber networks with proven extraordinary telecommunication capabilities.

In a recent study published in Optica, and selected to appear on the cover of the August 2018 issue, ICFO researchers Alessandro Seri, Darío Lago-Rivera, and Dr. Andreas Lenhard, led by Dr. Margherita Mazzera and ICREA Prof at ICFO Hugues de Riedmatten, in collaboration with Dr. Giacomo Corrielli and Dr. Roberto Osellame from IFN-CNR in Milan, report on the demonstration of a novel platform for quantum single-photon light storage based on laser written waveguides.

In their experiment, the team of researchers fabricated the waveguides in a Pr3+:Y2SiO5 crystal using femtosecond laser micromachining (FLM) in a new writing regime. They showed that the fabrication of these waveguides preserves the measured spectroscopic properties of Pr3+. They implemented a quantum storage protocol for heralded single photons, demonstrating excited-state storage times 100 times longer than in previous waveguide demonstrations and with improved confining capabilities. With respect to other waveguide realization, the FLM features unique 3D fabrication capabilities. Even more, the very good matching between the waveguide mode and that of standard single-mode optical fibers promise that these Pr3+:Y2SiO5 samples could be adhered directly to fiber patch cords with very low coupling losses, excellent for telecommunication setups.

The results of this study have shown that these fabricated system promise to effectively fulfil the requirements for efficient and scalable integrated quantum storage devices.