Quantum Storage of Frequency-Multiplexed Heralded Single Photons

Quantum memories for light are important devices in quantum information science, in particular for applications such as quantum networks and quantum repeaters. It has been predicted that multimode quantum memories able to store independently multiple modes would greatly help the scaling of quantum networks by decreasing the entanglement generation time between remote quantum nodes. Current research focuses mostly on time multiplexing in rare-earth doped crystals and in spatial multiplexing in atomic gases. Beyond these demonstrations, rare-earth doped crystals, thanks to their large inhomogeneous broadening, represent a unique quantum system which could also add another degree of freedom for multiplexing, the storage of multiple frequency modes. In this contribution, we report on the first demonstration of quantum storage of a frequency multiplexed single photon into a laser-written waveguide integrated in a Pr
³⁺
:Y
₂
SiO
₅
crystal. The great advantage of using a confined waveguide for this task is that the power required to prepare the quantum memory is strongly reduced due to the increased light-matter interaction in the waveguide. This enables simultaneous preparation of several memories at different frequencies, with a moderate laser power.