Investment in quantum technology has literally taken-off in recent years. In 2016 China launched their first quantum communication satellite, and the billion euro QuantERA initiative has just begun in Europe. Both these programs have highlighted the need for a future quantum Internet, which can connect distant quantum computers and transmit encrypted information.
Quantum memories for light will be essential elements in these future networks. These memories operate by reversibly mapping the quantum state of light onto the quantum transitions of a material system. For fibre-based networks, the quantum coherence times of these transitions must be long compared to the network transmission times, approximately 100ms for a global fibre network. Until recently, the longest coherence time for a quantum memory in the 1550 nm fibre telecom band was only 1 us.
Here I will present our results with the rare earth doped material 167Er:YSO. In a large magnetic field this material has demonstrated a hyperfine coherence time of 1.3 seconds. With optical absorption of 70 dB/cm at 1538 nm, it could become the first practical quantum memory for fibre telecom networks.