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In our experiments we study nonclassical light, whose behavior is essentially quantum and cannot be understood in the framework of classical optics. The bright squeezed vacuum and entangled photons are both typical examples. Both are generated through the nonlinear process of parametric down-conversion.

Entangled photons are famous for disproving Einstein’s phrase ‘God does not play dice’. Each photon of an entangled pair, generally, does not have any particular frequency, momentum, or polarization before the measurement. It is therefore similar to a die before it is thrown. However, there is strict correlation between the photons of a pair. This property is used in metrology, communications, and imaging.

Bright squeezed vacuum appears when there are so many entangled photon pairs that they overlap. Surprisingly, large groups of photons will still manifest nonclassical properties. We try to learn how to better measure them and to apply their properties in quantum information, imaging, and metrology.