It is a fundamental challenge in quantum optics to deterministically generate indistinguishable single photons through non-deterministic nonlinear optical processes, due to the intrinsic coupling of single- and multi-photon-generation probabilities in these processes. Actively multiplexing photons generated in many temporal modes can decouple these probabilities, but key issues are to minimize resource requirements to allow scalability, and to ensure indistinguishability of the generated photons. Here we demonstrate the multiplexing of photons from four temporal modes solely using fibre-integrated optics and off-the-shelf electronic components. We show a 100% enhancement to the single-photon output probability without introducing additional multi-photon noise. Photon indistinguishability is confirmed by a fourfold Hong–Ou–Mandel quantum interference with a 91±16% visibility after subtracting multi-photon noise due to high pump power. Our demonstration paves the way for scalable multiplexing of many non-deterministic photon sources to a single near-deterministic source, which will be of benefit to future quantum photonic technologies.

An interesting feature of microstructured optical fibers (MOFs) is that their properties can be adjusted by filling or coating of the holes. Some applications require selective filling or coating, which has proved experimentally demanding. We demonstrate selective coating of MOFs with metal and use it to fabricate an in-fiber absorptive polarizer.

Photonic chip based time-bin entanglement has attracted significant attention because of its potential for quantum communication and computation. Useful time-bin entanglement systems must be able to generate, manipulate and analyze entangled photons on a photonic chip for stable, scalable and reconfigurable operation. Here we report the first time-bin entanglement photonic chip that integrates time-bin generation, wavelength demultiplexing and entanglement analysis. A two-photon interference fringe with an 88.4% visibility is measured (without subtracting any noise), indicating the high performance of the chip. Our approach, based on a silicon nitride photonic circuit, which combines the low-loss characteristic of silica and tight integration features of silicon, paves the way for scalable real-world quantum information processors.Entanglement is at the heart of photonic quantum technologies such as secure communication [1], super-resolution metrology [2], and powerful computation [3]. Photons are usually entangled in one of three degrees of freedom: polarization, optical path, or time bin. On-chip polarization entangled photon sources have been reported [4,5], but only the components for photon generation were on-chip due to the difficulty of integrating polarization analysis devices. Chip-scale optical path entangled photon generation and analysis [6], and teleportation [7] have seen rapid development, aiming for on-chip quantum computation. Time-bin entanglement is of particular interest because it (i) can be extended to higher dimensions for computation [8]; (ii) is insensitive to polarization fluctuation and polarization dispersion, and therefore very promising for long distance quantum key distribution (QKD) [1]; and (iii) is naturally compatible with integrated optics: photons can be generated in nonlinear waveguides, entangled and analyzed using on-chip unbalanced Mach-Zehnder interferometers (UMZIs) [9,10].For time-bin entanglement to be useful in the real world, the onchip integration of the entire entanglement system is essential. The high performance of the entanglement system not only relies on photon generation, but also hinges on the compactness, scalability and reconfigurability of the photonic circuit that generates the time bins, demultiplex the photons and analyze the entanglement. Refs [9] and [10] reported photon generation from compact silicon devices, but the wavelength demultiplexing was off chip, and entanglement analysis was based on silica waveguides, which have large bending radii due to their low index contrast. These features are incompatible with high density integration.In this paper we report, for the first time, a time-bin entanglement photonic chip that integrates time-bin generation, wavelength demultiplexing and entanglement analysis. Our demonstration was based on a high index contrast silicon nitride (Si3N4) circuit. The waveguide bending radii were reduced from millimeter (for silica) to micrometer scale while maintaining low losses, making high density integration possibl...

Rectocele depth is associated with symptoms of obstructed defecation. A "clinically significant" rectocele may be defined as a diverticulum of the rectal ampulla of ≥15 mm in depth, although poor test characteristics limit clinical utility of this cut-off.