Frequency upconversion of squeezed vacuum states of light

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Squeezed states of light are at the very heart of quantum physics, a fact which is e.g. revealed by the presents of entanglement between their sideband fields. In many proof-of-principle experiments in particular squeezed vacuum states of light have been used to reduce the photon counting noise (shot-noise) in quantum metrology. Whereas squeezed light at near infra-red wavelengths can efficiently be generated by parametric downconversion in nonlinear crystals, this approach fails for efficient squeezed light generation at visible or even at UV wavelengths. Shorter wavelengths, however, are desirable in metrology, because they provide a higher phase signal and also a higher signal-to-shot-noise-ratio for a given light power. In this project squeezed vacuum states of light will be generated at 532nm by frequency upconverting a squeezed field at 1550nm for the first time. The light will be used to demonstrate a table-top laser interferometer at 532nm with a sensitivity better than the shot-noise limit. A quantitative analysis of the interferometer will prove that the absolute displacement sensitivity is better than the sensitivity of an identical interferometer operated with the same laser power and the same squeezing factor, but at a larger wavelength. The results of this project will also have applications in quantum information science since the frequency upconversion of nonclassical light may provide the interface between telecommunication wavelengths and quantum storage devices.