The extent to which the intense light generated by an unseeded, high-gain optical parametric ampli®er retains the desired quantum statistical properties of the individual photon pairs generated by spontaneous parametric downconversion is analysed. It is shown that certain but not all of these properties are retained, with important implications for applications of quantum optics.

It was recently suggested [1] that parametric resonance during the reheating phase of an inflationary Universe [2–4] may lead to an exponential amplification of superHubble scale gravitational fluctuations. If true, this would affect the usual predictions of inflationary models for observables such as the matter power spectrum and the spectrum of cosmic microwave anisotropies. In particular, it...

The purpose of this report is to place in proper perspective the role that the modern semiconductor diode lownoise amplifier and converter have in the amplification of extremely small signals. There is a discussion of the fundamental principles of parametric amplification, and a quantitive treatment which is valid in the limit of very high Q diodes. Design formulas from the literature are given...

We study the adiabatic density perturbation in the oscillating inflation, proposed by Damour and Mukhanov. The recent study of the cosmological perturbation during reheating shows that the adiabatic fluctuation behaves like as the perfect fluid and no significant amplification occurs on super-horizon scales. In the oscillating inflation, however, the accelerated expansion takes place during the...

In conventional quantum nondemolition measurements, the interaction between signal and probe preserves the measured variable. Alternatively, it is possible to restore the original value of the variable by feedback. In this paper, we describe a quantum nondemolition measurement of a quadrature component of the light field using a feedback compensated beam splitter. The noise induced by the vacuu...

*Correspondence: [email protected] Department of Physics, ETH Zürich, Zürich, 8093, Switzerland Abstract One of the central challenges in the development of parametric amplifiers is the control of the dynamic range relative to its gain and bandwidth, which typically limits quantum limited amplification to signals which contain only a few photons per inverse bandwidth. Here, we discuss the c...