6. Conclusion

The use of active crystals for quantum information processing requires excellent mastery of the material, from design to manufacture. Spectroscopic properties must be matched to information manipulation techniques. The interaction between radiation and matter is a common thread that reflects the versatility of light, both as a privileged carrier of information and as a tool for controlling atomic properties.

Quantum storage of an optical signal is the most advanced application. It draws heavily on the maturity of crystalline materials available, for example, for laser applications. It also benefits from the major advances made with atomic vapors, which are intrinsically well isolated from the environment and traditionally used in atomic physics. This synergy between two fields is a real source of theoretical breakthroughs.

The realization...