Spectrally pure heralded single photons by spontaneous four-wave mixing in a fiber: reducing impact of dispersion fluctuations

Mitigating indistinguishability issues in photon pair sources by delayed-pump intermodal four wave mixing

Large arrays of independent, pure and identical heralded single photon sources are an important resource for linear optical quantum computing protocols. In the race towards the development of increasingly ideal sources, delayed-pump intermodal four wave mixing (IFWM) in multimode waveguides has recently emerged as one of the most promising approaches. Despite this, fabrication imperfections still spoil the spectral indistinguishability of photon pairs from independent sources. Here we show that by tapering the width of the waveguide and by controlling the delay between the pump pulses, we add additional spectral tunability to the source while still inheriting all the distinctive metrics of the IFWM scheme. This feature is used to recover spectral indistinuishability in presence of fabrication errors. Under realistic tolerances on the waveguide dimensions, we predict >99.5% indistinguishability between independent sources on the same chip, and a maximum degradation of the heralded Hong-Ou-Mandel visibility <0.35%.

Multiple modal and wavelength conversion process of a 10-Gbit/s signal in a 6-LP-mode fiber

We demonstrate experimentally a simultaneous threefold modal and wavelength conversion process of a 10-Gbit/s On/Off keying signal in a 1.8-km long graded-index 6-LP-mode fiber. The principle of operation is based on a phase-matched inter-modal four-wave mixing phenomenon occurring between the fundamental mode and 3 higher-order modes of the fiber. The converted signals show well-opened eye-diagrams and error-free processing.

Shape-preserving and unidirectional frequency conversion by four-wave mixing

In this work, we investigate the properties of four-wave mixing Bragg scattering driven by orthogonally polarized pumps in a birefringent waveguide. This configuration enables a large signal conversion bandwidth, and allows strongly unidirectional frequency conversion as undesired Bragg-scattering processes are suppressed by waveguide birefringence. Moreover, we show that this form of Bragg scattering preserves the (arbitrary) signal pulse shape, even when driven by pulsed pumps.