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.

We develop integrated spontaneous photon sources in silicon photonics simultaneously satisfying all requirements for large-scale photonic quantum computing: 0:9904 ± 0:0006 spectral purity, 0:985 ± 0:002 indistinguishability, > 90% heralding efficiency, and 0:96 ± 0:02 on-chip heralded quantum interference visibility.

Reliable randomness is a core ingredient in algorithms and applications ranging from numerical simulations to statistical sampling and cryptography. The outcomes of measurements on entangled quantum states can violate Bell inequalities [1], thus guaranteeing their intrinsic randomness. This constitutes the basis for certified randomness generation, which applies to untrusted devices [2,3]. However, this certification requires several spacelike separated devices, making it unfit for a compact apparatus [4]. Here we provide a general method for certified randomness generation on a small-scale application-ready device and perform an integrated photonic demonstration combining a solid-state emitter and a glass chip. In contrast to most existing certification protocols, which in the absence of spacelike separation are vulnerable to loopholes inherent to realistic devices [5], the protocol we implement accounts for information leakage to be compatible with emerging compact scalable devices. We demonstrate a 2-qubit photonic device that achieves the highest standard in randomness yet is cut out for real-world applications. The full 94.5-hour-long stabilized process harnesses a bright and stable single-photon quantum-dot based source, feeding into a reconfigurable photonic chip, with stability in the milliradian range on the implemented phases and consistent indistinguishably of the entangled photons above 93%. Using the contextuality framework [6], we robustly certify the highest standard of private randomness generation, i.e. cryptographic security even in the presence of quantum side information. This is a prototype for the controlled alliance of quantum hardware and protocols to reconcile practical limitations and device-independent certification.