Quantum noise of ultrastable bright twin beams

摘要

We investigate experimentally the number and phase quantum noises of the light emitted by an ultrastable nondegenerate optical parametric oscillator (OPO) above threshold. Strong intensity correlations at the photon level - number-difference squeezing or twin beams - have already been observed by several groups. We have recently observed the twin-beam interference of a classically phase-locked OPO and have shown that the phase-difference is antisqueezed, as expected from the number-phase Heisenberg (in)equality. In this paper we describe the realization of a stable classical measurement of the joint quadratures of an OPO, as part of our ongoing effort to generate ultrastable EPR light beams simultaneously squeezed in number difference and phase sum.