Tuning quantum correlations with intracavity photonic crystals

Abstract

We show how to tune quantum noise in nonlinear systems by means of periodic spatial modulation. We prove that the introduction of an intracavity photonic crystal in a multimode optical parametric oscillator inhibits and enhances light quantum fluctuations. Furthermore, it leads to a significant noise reduction in field quadratures, robustness of squeezing in a wider angular range, and spatial entanglement. These results have potential benefits for quantum imaging, metrology, and quantum information applications and suggest a control mechanism of fluctuations by spatial modulation of interest also in other nonlinear systems.

Spatial fluctuations in an optical parametric oscillator below threshold with an intracavity photonic crystal

“…The main difference with respect to a generic OPO [39,41] is that in a PCOPO, the intracavity photonic crystal gives rise to a spatial modulation of the cavity detunings 0,1 (x) [38]. This constitutes a breaking of the translational symmetry of the system, with deep consequences both in the macroscopic field dynamics and in the correlations between fluctuations.…”

“…1 of Ref. [38]. The intracavity dynamics of this PCOPO can be described in terms of continuous boson spatial modes 0,1 (x,t) at frequencies ω 0,1 , x ∈ R 2 .…”

“…In Ref. [38], numerical results about quantum effects both below and above threshold were reported, based on a simulation of the quantum-field dynamics in the Q representation. From the methodological point of view, this description, as discussed in Ref.…”

“…[38], we presented a study based on the numerical analysis of quantum fluctuations using a Langevin treatment valid both above and below threshold [39]. We showed that the quantum correlations can be tuned by means of this PC, obtaining noise reduction in field quadratures, robustness of squeezing in a wider angular range, and, most remarkably, an improvement of entanglement above threshold [38]. In this paper, we present analytical results valid below the parametric threshold and based on linear and few-mode approximations in good agreement with numerical simulations of the full model.…”

“…II, we present the model of a PCOPO using linear and few-mode approximations for the light fluctuations below threshold giving the output signal field in terms of the input one. We also introduce a set of nonlinear Langevin equations [38,39] that we numerically simulate to test our approximations. In Sec.…”