We report the first demonstrations of both quadrature squeezed vacuum and
photon number difference squeezing generated in an integrated nanophotonic
device. Squeezed light is generated via strongly driven spontaneous four-wave
mixing below threshold in silicon nitride microring resonators. The generated
light is characterized with both homodyne detection and direct measurements of
photon statistics using photon number-resolving transition edge sensors. We
measure 1.0(1)~dB of broadband quadrature squeezing (∼4~dB inferred
on-chip) and 1.5(3)~dB of photon number difference squeezing (∼7~dB
inferred on-chip). Nearly-single temporal mode operation is achieved, with raw
unheralded second-order correlations g(2) as high as 1.87(1) measured
(∼1.9~when corrected for noise). Multi-photon events of over 10 photons
are directly detected with rates exceeding any previous quantum optical
demonstration using integrated nanophotonics. These results will have an
enabling impact on scaling continuous variable quantum technology.Comment: Significant improvements and updates to photon number squeezing
results and discussions, including results on single temporal mode operatio