An elementary 158 km long quantum network connecting room temperature quantum memories *

First-generation long-distance quantum repeater networks require quantum memories to perform quantum-interference-mediated entanglement generation operations [1]. The ability to demonstrate these interconnections using real-life telecommunication fiber connections in a long-distance setting is paramount to realize a scalable quantum internet.

 

We present our recent results obtained in the quantum network prototype connecting quantum laboratories between Stony Brook University and Brookhaven National Laboratory [2]. First, we characterize the non-linear frequency conversion of single-photon-level signals between the 795 and 1324 rubidium atomic lines, using a diamond atomic scheme. We will also report on our observation of Hong-Ou-Mandel (HOM) interference between indistinguishable telecom photons produced in two independent room temperature quantum memories, separated by a distance of 158 km. We obtained interference visibilities after long-distance propagation of V=(38±2)% for single-photon level experimental inputs. Finally, we will present our preliminary results towards achieving long-distance entanglement between the two independent room temperature quantum memories. 

 

This first-of-its-kind long distance quantum network is envisioned to evolve into a large-scale memory-assisted entanglement distribution quantum network, the basis for inter-city quantum communication.

[1] Duan, LM., Lukin, M., Cirac, J. et al. Long-distance quantum communication with atomic ensembles and linear optics. Nature 414, 413–418 (2001).

 

[2] Du, D., Stankus, P., Saira, O.P., Flament, M., Sagona-Stophel, S., Namazi, M., Katramatos, D. and Figueroa, E., 2021. An elementary 158 km long quantum network connecting room temperature quantum memories. arXiv preprint arXiv:2101.12742.