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Broadband waveguide quantum memory for entangled photons


The reversible transfer of quantum states of light into and out of matter constitutes an important building block for future applications of quantum communication: it will allow the synchronization of quantum information1, and the construction of quantum repeaters2 and quantum networks3. Much effort has been devoted to the development of such quantum memories1, the key property of which is the preservation of entanglement during storage. Here we report the reversible transfer of photon–photon entanglement into entanglement between a photon and a collective atomic excitation in a solid-state device. Towards this end, we employ a thulium-doped lithium niobate waveguide in conjunction with a photon-echo quantum memory protocol4, and increase the spectral acceptance from the current maximum5 of 100 megahertz to 5 gigahertz. We assess the entanglement-preserving nature of our storage device through Bell inequality violations6 and by comparing the amount of entanglement contained in the detected photon pairs before and after the reversible transfer. These measurements show, within statistical error, a perfect mapping process. Our broadband quantum memory complements the family of robust, integrated lithium niobate devices7. It simplifies frequency-matching of light with matter interfaces in advanced applications of quantum communication, bringing fully quantum-enabled networks a step closer.

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Figure 1: Schematics of the experimental set-up.
Figure 2: The storage medium.
Figure 3: Measurement of density matrices.


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This work is supported by NSERC, QuantumWorks, General Dynamics Canada, iCORE (now part of Alberta Innovates), CFI, AAET and FQRNT. We thank C. La Mela, T. Chanelière, T. Stuart, V. Kiselyov and C. Dascollas for help during various stages of the experiment, C. Simon, K. Rupavatharam and N. Gisin for discussions, and A. Lvovsky for lending us a single-photon detector.

Author information




The Ti:Tm:LiNbO3 waveguide was fabricated and characterized at room temperature by M.G., R.R. and W.S. The photon-pair source was built by J.J., J.A.S. and F.B., the AFC memory set-up was developed by E.S. and N.S., and the complete experiment was conceived and directed by W.T. The measurements and the analysis were done by E.S., N.S., J.J., J.A.S., D.O. and W.T., and W.T., E.S., N.S., J.J., J.A.S. and D.O. wrote the paper. E.S., N.S., J.J. and J.A.S. contributed equally to this work.

Corresponding author

Correspondence to Wolfgang Tittel.

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The authors declare no competing financial interests.

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Supplementary Information

The file contains Supplementary Text and Data, Supplementary Tables 1-2, Supplementary Figure 1 with a legend and additional references. (PDF 317 kb)

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Saglamyurek, E., Sinclair, N., Jin, J. et al. Broadband waveguide quantum memory for entangled photons. Nature 469, 512–515 (2011).

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