Developing indistinguishable heralded single-photon sources in silicon photonics
December 13, 2018 @ 3:00 pm
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High visibility quantum interference between multiple single-photons is a key prerequisite for linear optical quantum computing, networking and relevant technologies. To date, numerous experiments have investigated the interference between multiple on-chip silicon photonics sources, but all have been restricted to the generation of a single path-entangled photon pair as 2-fold coincidence measurements . Interfering heralded singles photons generated from independent sources as 4-fold coincidence measurements—a true measure of indistinguishability—has been limited to waveguide sources [2-3]. However, the indistinguishability of heralded single photons from micro-ring resonators has not been measured in any photonic platform including silicon. Resonant enhancement in micro-ring resonators naturally enables brighter, purer and more indistinguishable single photon productions without any tight spectral filtering compared to waveguide sources. Here we report on-chip indistinguishability measurements of heralded single-photons at telecom wavelengths from independent micro-ring resonator sources. We take an important step in the realization of integrated linear optical quantum computing by combining on-chip generation, spectral demultiplexing and interference of heralded single-photons from independent sources. We measured the raw heralded two-photon interference fringe visibility as 72±3% from the 4-fold coincidences . A low resolution joint spectral intensity measurement estimates the upper bound of purity to be 96% which agrees with our simulation. We found that the multi-pair emission is the primary cause of visibility degradation. In addition, we have measured the purity and indistinguishability of waveguide sources as a function of spectral filtering achieving 86±1% raw indistinguishability. Using these measurements, we compared and identified pathways to improve nanowire waveguides and micro-ring resonators single photon sources in terms of brightness, purity and indistinguishability.
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