Poster: A Novel Europium Crystal for Quantum Memory and Integrated Photonics

A promising carrier of quantum information is the optical photon, chosen for its transmissibility at room temperature and long-distance coherence. For networking, it is crucial that such photons be stored and released in a controlled manner. Various methods have been employed to achieve such a “quantum memory,” and here we focus on photon echoes and lambda-type schemes that store collective excitations as long-lived spin-waves. These strategies store photons via interaction with atomic ensembles (in vacuum or solid-state), so the properties of constituent atoms or ions significantly influence the performance of the memory. Rare-earth atoms have been employed as crystal dopants or stoichiometric lattice-components for their long hyperfine spin transitions and low inhomogeneous broadening, attributable to intrinsic shielding of their 4f electrons. Stoichiometric and molecular rare-earth crystals are particularly appealing due to their record high emitter density, potential for reduced optical inhomogeneity, and ability to host controlled emitter-emitter interactions. Here we investigate one such material, sodium europium tetraiodate, not only for the desirable properties of the Eu³⁺ ions therein, but also due to its capacity for exfoliation and on-chip integration. We target its ⁷F₀ → ⁵D₀ optical transition because of its narrow linewidth and coherent emission. The hyperfine spectrum along with preliminary quantum memory performance metrics are discussed.