Generation of quantum-certified random numbers using on-chip path-entangled single photons from an LED

Single-photon entanglement is a peculiar type of entanglement in which two or more degrees of freedom of a single photon are correlated quantum-mechanically. Here, we demonstrate a photonic integrated chip able to generate and manipulate single-photon path-entangled states, using a commercial red LED as light source.A Bell test, in the Clauser, Horne, Shimony, and Holt(CHSH) form, is performed to confirm the presence of entanglement, resulting in a maximum value of the CHSH correlation parameter equal to 2.605 ± 0.004.This allows us to use it as an integrated semi-device independent quantum random number generator able to produce certified random numbers. The certification scheme is based on a Bell’s inequality violation and on a partial characterization of the experimental setup, without the need of introducing any further assumptions either on the input state or on the particular form of the measurement observables. In the end a min-entropy of 33% is demonstrated.

Do different kinds of photon-pair sources have the same indistinguishability in quantum silicon photonics?

In the same silicon photonic integrated circuit,we compare two types of integrated degenerate photon-pair sources(microring resonators and waveguides)using Hong–Ou–Mandel(HOM)interference experiments.Two nominally identical microring resonators are coupled to two nominally identical waveguides,which form the arms of a Mach–Zehnder interferometer.This is pumped by two lasers at two different wavelengths to generate,by spontaneous four-wave mixing,degenerate photon pairs.In particular,the microring resonators can be thermally tuned in or out of resonance with the pump wavelengths,thus choosing either the microring resonators or the waveguides as photon-pair sources,respectively.In this way,an on-chip HOM visibility of 94%with microring resonators and 99%with straight waveguides is measured upon filtering.We compare our experimental results with theoretical simulations of the joint spectral intensity and the purity of the degenerate photon pairs.We verify that the visibility is connected to the sources’indistinguishability,which can be quantified by the overlap between the joint spectral amplitudes(JSA)of the photon pairs generated by the two sources.We estimate a JSA overlap of 98%with waveguides and 89%with microring resonators.