Energy-efficient entanglement generation and readout in a spin-photon interface

We consider a quantum interface made of a spin coupled to a one-dimensional atom, and study its potential for energy-efficient entanglement generation and readout. We show that quantum superpositions of zero and single-photon states outperform coherent pulses of light, producing more entanglement with the same energy. Entanglement is generally distributed over the polarisation and the temporal degrees of freedom, except for quasi-monochromatic pulses whose shape is preserved by light-matter interaction. The energetic advantage provided by quantum pulses over coherent ones is maintained when information on the spin state is extracted at the classical level. The proposed schemes are robust against imperfections in state-of-the-art semi-conducting devices.