Ultrabroadband quantum interface for telecom-wavelength single-photon qubits using a semiconductor quantum dot ensemble

We demonstrate the coherent transfer and retrieval of ultrabroadband (terahertz range) time-bin qubits to a quantum dot ensemble using photon echo technique at telecommunication wavelength. The time-bin qubits are implemented with 1-ps weak coherent pulses at the single photon level. The transfer and retrieval fidelity of time-bin qubits is estimated to be higher than 95 % for 200-ps storage time.