Efficient storage of multidimensional telecom photons in a solid-state quantum memory

Efficient storage of telecom-band quantum optical information represents a crucial milestone for establishing distributed quantum optical networks. Erbium ions in crystalline hosts provide a promising platform for telecom quantum memories; however, their practical applications have been hindered by demanding operational conditions, such as ultra-high magnetic fields and ultra-low temperatures. In this work, we demonstrate the storage of telecom photonic qubits encoded in polarization, frequency, and time-bin bases. Using the atomic frequency comb protocol in an Er 3+ -doped crystal, we developed a memory initialization scheme that improves storage efficiency by over an order of magnitude. The observed results were made possible by the deliberate selection of the pumping sequence and the minimization of lattice interactions, to the extent possible without the use of dilution refrigerators or superconducting magnets.