Nonclassical two-photon interferometry and lithography with high-gain parametric amplifiers - art. no. 043802

Optical parametric amplification is a process that leads to the generation of quantum states of light. In the limit of low single-pass gain, this proc ess is often referred to as parametric down conversion, and produces entang led two-photon states. Such states have played a key role in recent studies of quantum optical effects such as quantum teleportation. As the gain of t he parametric amplification process is increased, the generated light field still possesses strong quantum correlations. but not of the sort associate d with two-photon states. Here we present an analysis of the output state o f a parametric amplifier as a function of the single-pass gain, and we find certain signatures of quantum light (such as the vanishing of the coincide nce rate in a Hong-OuMandel interferometer) disappear in the high-gain limi t, whereas others (such as the existence of two-photon interference fringes ) remain. Consequently, the intense light field generated by a high-gain pa rametric amplifier can be utilized in such applications of quantum optics.