Quantum communications rely on the distribution and the storage of qubits of information, which are usually very sensitive against decoherence. A good candidate to code this information for long-distance communication is the photon, regarding its low interaction with the environment and its high speed. However, current state-of-the-art optical fibers limit the maximum distance of protocols to a few hundreds of kilometers, which imposes the development of the so-called 'quantum repeater' [1].
In this presentation, I will show the latest achievements towards the implementation of the quantum repeater in a solid-state system: a crystal doped with europium ions. This platform allowed us to demonstrate long-lived on-demand quantum memories at the single photon level with a temporal multiplexing capacity [2], and enabled us to implement a DLCZ-like protocol [3], opening the path towards a solid-state multimode quantum repeater.
With this protocol, we have witnessed quantum correlations between two photons at 580 nm temporally separated by a tunable delay of 1 ms. By using the AFC technique [4] to rephase the atomic excitations, a temporal multiplexing capacity of our protocol of 10 modes could be reached.
We also explore further paths of improvements regarding the maximum storage duration of our quantum memories by investigating the dependence of the atomic structure against magnetic field [5]. Experimental improvements are also investigated to open the path towards long-distance and long-duration quantum communication.
[1] N. Sangouard, C. Simon, H. de Riedmatten and N. Gisin, Rev. Mod. Phys. 83, 33 (2011)
[2] P. Jobez et al., Phys. Rev. Lett. 114, 230502 (2015)
[3] C. Laplane, P. Jobez, J. Etesse, N. Gisin and M. Afzelius, Phys. Rev. Lett. 118, 210501 (2017)
[4] M. Afzelius, C. Simon, H. de Riedmatten and N. Gisin, Phys. Rev. A 79, 052329 (2009)
[5] E. Zambrinni Cruzeiro, J. Etesse, A. Tiranov, P.-A. Bourdel, F. Fröwis, P. Goldner, N. Gisin and M. Afzelius, Phys. Rev. B 97, 094416 (2018)
