Persistent atomic frequency comb based on Zeeman sub-levels of an erbium-doped crystal waveguide
Mohsen Falamarzi Askarani (TU Delft - QID/Tittel Lab, University of Calgary)
Thomas Lutz (ETH Zürich, University of Calgary)
Marcelli Grimau Puigibert (University of Calgary, University of Basel)
Neil Sinclair (California Institute of Technology, University of Calgary)
Daniel Oblak (University of Calgary)
Wolfgang Tittel (TU Delft - QID/Tittel Lab, University of Calgary, TU Delft - Quantum Communications Lab)
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Abstract
Long-lived sub-levels of the electronic ground-state manifold of rare-earth ions in crystals can be used as atomic population reservoirs for photon echo-based quantum memories. We measure the dynamics of the Zeeman sublevels of erbium ions that are doped into a lithium niobate waveguide, finding population lifetimes at cryogenic temperatures down to 0.7 K as long as seconds. Then, using these levels, we prepare and characterize atomic frequency combs (AFCs), which can serve as a memory for quantum light at 1532 nm wavelength. The results allow predicting a 0.1% memory efficiency, limited mainly by unwanted background absorption that we believe to be caused by excitation-induced erbium spin flips and frequency shifting due to two-level systems or non-equilibrium phonons. Hence, while it should be possible to create an AFC-based quantum memory in Er3 +:Ti4 +:LiNbO3, improved crystal growth together with optimized AFC preparation will be required to make it suitable for applications in quantum communication.