While integrated photonics is a robust platform for quantum information processing, architectures for photonic quantum computing place stringent demands on high quality information carriers. Sources of single photons that are highly indistinguishable and pure, that are either near-deterministic or heralded with high efficiency, and that are suitable for massmanufacture, have been elusive. Here, we demonstrate on-chip photon sources that simultaneously meet each of these requirements. Our photon sources are fabricated in silicon using mature processes, and exploit a dual-mode pump-delayed excitation scheme to engineer the emission of spectrally pure photon pairs through intermodal spontaneous fourwave mixing in low-loss spiralled multi-mode waveguides. We simultaneously measure a spectral purity of 0.9904 ± 0.0006, a mutual indistinguishability of 0.987 ± 0.002, and >90% intrinsic heralding efficiency. We measure on-chip quantum interference with a visibility of 0.96 ± 0.02 between heralded photons from different sources.

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Silicon photonics is a technology based on fabricating integrated optical circuits by using the same paradigms as the dominant electronics industry. After twenty years of fervid development, silicon photonics is entering the market with low cost, high performance and mass-manufacturable optical devices. Until now, most silicon photonic devices have been based on linear optical effects, despite the many phenomenologies associated with nonlinear optics in both bulk materials and integrated waveguides. Silicon and silicon-based materials have strong optical nonlinearities which are enhanced in integrated devices by the small cross-section of the high-index contrast silicon waveguides or photonic crystals. Here the photons are made to strongly interact with the medium where they propagate. This is the central argument of nonlinear silicon photonics. It is the aim of this review to describe the state-of-the-art in the field. Starting from the basic nonlinearities in a silicon waveguide or in optical resonator geometries, many phenomena and applications are described—including frequency generation, frequency conversion, frequency-comb generation, supercontinuum generation, soliton formation, temporal imaging and time lensing, Raman lasing, and comb spectroscopy. Emerging quantum photonics applications, such as entangled photon sources, heralded single-photon sources and integrated quantum photonic circuits are also addressed at the end of this review.

In this paper, we investigate the impact of Ge-enrichment coupled to N-or C-doping in Ge 2 Sb 2 Te 5 based materials on low-resistance state (LRS or SET) performance combined with high-resistance state (HRS or RESET) high-temperature data retention (HTDR) in Phase-Change Memories (PCM). These innovative materials have been integrated in state-of-the-art memory cell prototypes. For the first time, a focus on the trade-off between SET stability (which is affected by resistance drift) and RESET HTDR is proposed. This aspect has been extensively characterized. Through physico-chemical analysis and electrical characterization we demonstrate the need for a specific "programming-current-vs-time-profile" to finally achieve an LRS stable at high-working temperature with programming times compatible with industrial applications. Finally, the reliability of the HRS and the LRS obtained with our optimized programming procedure has been demonstrated through Reflow Soldering Temperature Profile (RSTP) tests. The last result fully enables PCM for embedded applications, in which data integrity after the peak temperature of reflow soldering must be ensured.