Towards the integration of a PIC-based entangled photon-pair source and an ensemble-based quantum memory compatible with the telecommunication C-band

Reaching a quantum internet of global scale will require a hybrid architecture of ground and satellite quantum repeater nodes [1]. The functional blocks of a generalized quantum repeater are four: the quantum channel; the Bell State measurement; the source of entanglement; and the quantum memory. Over the last 40 years, the technological achievements towards the development of these functional blocks can be categorized in epochs: the first epoch is characterized by the control of a single quantum system, such as the demonstration of entangled photon-pair emission from a non-linear material [2], or the coherent control of the spin in a colour-centre with an optical interface [3]; the second epoch involves the combined control of two quantum systems based on the same platform, such as the three-node network experiments with Rydberg atoms [4] and colour-centres [5]; the third epoch will usher demonstrations of combined control over different quantum systems. This presentation will detail the third-epoch roadmap towards the integration of an entangled photon-pair source (EPPS) and an ensemble-based quantum memory, both operating within the telecommunication C-band. The EPPS leverages the high quality factor of a micro-ring resonator built on a silicon-oninsulator (SOI) platform to achieve high photon-pair generation rates based on spontaneous four-wave mixing (SFWM). Active control of the pair emission wavelength allows preparing photons that fall within the bandwidth of an atomic frequency comb (AFC) carved into the inhomogeously-broadened absorption line of an Erbium-doped Lithium Niobate crystal. The AFC quantum memory stores input photonic quantum states for a fixed storage time, after which it emits a socalled photon echo, so that non-classical correlations between the stored quantum state and its pair can be evaluated. Techniques to increase the spectral overlap between source and memory, as well as to improve the memory storage efficiency are defined in the roadmap. The demonstration of such an integration step will pave the way towards a quantum repeater architecture that finds applications both in ground and space links.