The quantum repeater protocol is a promising approach for implementing long-distance quantum communication and large-scale quantum networks. A key idea of the quantum repeater protocol is to use long-lived quantum memories to achieve an efficient entanglement connection between different repeater segments, with polynomial scaling. Here, we report an experiment that realizes the efficient connection of two quantum repeater segments via on-demand entanglement swapping through the use of two atomic quantum memories with storage times of tens of milliseconds. With the memory enhancement, acceleration in the scaling is demonstrated in the rate for a successful entanglement connection. Experimental realization of the entanglement connection of two quantum repeater segments with an efficient memory-enhanced scaling demonstrates a key advantage of the quantum repeater protocol, creating a cornerstone for the development of future large-scale quantum networks.
Subscribe to Journal
Get full journal access for 1 year
only $8.25 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.
The code used for quantum state tomography is available from the corresponding author upon reasonable request.
Kimble, H. J. The quantum internet. Nature 453, 1023–1030 (2008).
Briegel, H.-J., Dür, W., Cirac, J. I. & Zoller, P. Quantum repeaters: the role of imperfect local operations in quantum communication. Phys. Rev. Lett. 81, 5932–5935 (1998).
Duan, L.-M., Lukin, M. D., Cirac, J. I. & Zoller, P. Long-distance quantum communication with atomic ensembles and linear optics. Nature 414, 413–418 (2001).
Sangouard, N., Simon, C., de Riedmatten, H. & Gisin, N. Quantum repeaters based on atomic ensembles and linear optics. Rev. Mod. Phys. 83, 33–80 (2011).
Bennett, C. H. et al. Teleporting an unknown quantum state via dual classical and Einstein–Podolsky–Rosen channels. Phys. Rev. Lett. 70, 1895–1899 (1993).
Bennett, C. H. et al. Purification of noisy entanglement and faithful teleportation via noisy channels. Phys. Rev. Lett. 76, 722–725 (1996).
Hammerer, K., Sorensen, A. S. & Polzik, E. S. Quantum interface between light and atomic ensembles. Rev. Mod. Phys. 82, 1041–1093 (2010).
Chou, C.-W. et al. Measurement-induced entanglement for excitation stored in remote atomic ensembles. Nature 438, 828–832 (2005).
Chaneliere, T. et al. Storage and retrieval of single photons transmitted between remote quantum memories. Nature 438, 833–836 (2005).
Eisaman, M. D. et al. Electromagnetically induced transparency with tunable single-photon pulses. Nature 438, 837–841 (2005).
Simon, J., Tanji, H., Ghosh, S. & Vuletic, V. Single-photon bus connecting spin–wave quantum memories. Nat. Phys. 3, 765–769 (2007).
Chou, C.-W. et al. Functional quantum nodes for entanglement distribution over scalable quantum networks. Science 316, 1316–1320 (2007).
de Riedmatten, H., Afzelius, M., Staudt, M. U., Simon, C. & Gisin, N. A solid-state light–matter interface at the single-photon level. Nature 456, 773–777 (2008).
Yuan, Z.-S. et al. Experimental demonstration of a BDCZ quantum repeater node. Nature 454, 1098–1101 (2008).
Yu, Y. et al. Entanglement of two quantum memories via fibres over dozens of kilometres. Nature 578, 240–245 (2020).
Bernien, H. et al. Heralded entanglement between solid-state qubits separated by three metres. Nature 497, 86–90 (2013).
Moehring, D. L. et al. Entanglement of single-atom quantum bits at a distance. Nature 449, 68–71 (2007).
Stephenson, L. J. et al. High-rate, high-fidelity entanglement of qubits across an elementary quantum network. Phys. Rev. Lett. 124, 110501 (2020).
Slodička, L. et al. Atom–atom entanglement by single-photon detection. Phys. Rev. Lett. 110, 083603 (2013).
Hofmann, J. et al. Heralded entanglement between widely separated atoms. Science 337, 72–75 (2012).
Kaneda, F., Xu, F., Chapman, J. & Kwiat, P. G. Quantum-memory-assisted multi-photon generation for efficient quantum information processing. Optica 4, 1034–1037 (2017).
Bhaskar, M. K. et al. Experimental demonstration of memory-enhanced quantum communication. Nature 580, 60–64 (2020).
Azuma, K., Tamaki, K. & Lo, H.-K. All-photonic quantum repeaters. Nat. Commun. 6, 6787 (2015).
Li, Z.-D. et al. Experimental quantum repeater without quantum memory. Nat. Photon. 13, 644–648 (2019).
Hasegawa, Y. et al. Experimental time-reversed adaptive Bell measurement towards all-photonic quantum repeaters. Nat. Commun. 10, 378 (2019).
Zhao, Z. et al. Experimental realization of entanglement concentration and a quantum repeater. Phys. Rev. Lett. 90, 207901 (2003).
Ekert, A. K. Quantum cryptography based on Bell’s theorem. Phys. Rev. Lett. 67, 661–663 (1991).
Zhao, R. et al. Long-lived quantum memory. Nat. Phys. 5, 100–104 (2009).
Yang, S.-J., Wang, X.-J., Bao, X.-H. & Pan, J.-W. An efficient quantum light–matter interface with sub-second lifetime. Nat. Photon. 10, 381–384 (2016).
Dudin, Y. O., Zhao, R., Kennedy, T. A. B. & Kuzmich, A. Light storage in a magnetically dressed optical lattice. Phys. Rev. A 81, 041805 (2010).
Fleischhauer, M. & Lukin, M. D. Dark-state polaritons in electromagnetically induced transparency. Phys. Rev. Lett. 84, 5094–5097 (2000).
Stute, A. et al. Tunable ion–photon entanglement in an optical cavity. Nature 485, 482–485 (2012).
Yang, S.-J. et al. Highly retrievable spin–wave–photon entanglement source. Phys. Rev. Lett. 114, 210501 (2015).
Krutyanskiy, V. et al. Light–matter entanglement over 50 km of optical fibre. npj Quantum Inf. 5, 72 (2019).
Chang, W. et al. Long-distance entanglement between a multiplexed quantum memory and a telecom photon. Phys. Rev. X 9, 041033 (2019).
This work was supported by the National Key Research and Development Program of China (2016YFA0301902), the Beijing Academy of Quantum Information Sciences, the Frontier Science Center for Quantum Information of the Ministry of Education of China and the Tsinghua University Initiative Scientific Research Program. Y.K.W. acknowledges support from the Shuimu Tsinghua Scholar Program and the International Postdoctoral Exchange Fellowship Program.
The authors declare no competing interests.
Peer review information Nature Photonics thanks Bing Qi and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
About this article
Cite this article
Pu, YF., Zhang, S., Wu, YK. et al. Experimental demonstration of memory-enhanced scaling for entanglement connection of quantum repeater segments. Nat. Photonics 15, 374–378 (2021). https://doi.org/10.1038/s41566-021-00764-4