Entanglement and nonlocality between disparate solid-state quantum memories mediated by photons
Marcel.li Grimau Puigibert, Mohsen Falamarzi Askarani, Jacob H. Davidson, Varun B. Verma, Matthew D. Shaw, Sae Woo Nam, Thomas A. Lutz, Gustavo C. Amaral, Daniel Oblak, Wolfgang Tittel
Abstract
Entangling quantum systems with different characteristics through the exchange of photons is a prerequisite for building future quantum networks. Proving the presence of entanglement between quantum memories for light working at different wavelengths furthers this goal. Here, we report on a series of experiments with a thulium-doped crystal, serving as a quantum memory for 794-nm photons, an erbium-doped fiber, serving as a quantum memory for telecommunication-wavelength photons at 1535 nm, and a source of photon pairs created via spontaneous parametric down-conversion. Characterizing the photons after re-emission from the two memories, we find nonclassical correlations with a cross-correlation coefficient of g(12)((2)) = 53 +/- 8; entanglement preserving storage with input-output fidelity of F-IO approximate to 93 +/- 2%; and nonlocality featuring a violation of the Clauser-Horne-Shimony-Holt Bell inequality with S = 2.6 +/- 0.2. Our proof-of-principle experiment shows that entanglement persists while propagating through different solid-state quantum memories operating at different wavelengths.