Engineering multipartite entangled states in doubly pumped parametric down-conversion processes

TL;DR

This paper demonstrates the generation and control of multipartite entangled states in optical parametric down-conversion processes driven by two pump modes, with potential applications in quantum information processing.

Contribution

It introduces methods to produce and manipulate 3- and 4-partite entangled states in specific nonlinear optical setups using dual pump configurations.

Findings

Multipartite entangled states emerge as bright spots in the generated light.

State properties can be controlled by adjusting the relative pump intensities.

Two realistic experimental setups successfully produce and control these entangled states.

Abstract

We investigate the quantum state generated by optical parametric down-conversion in a $\chi^{(2) } $ medium driven by two noncollinear light modes. The analysis shows the emergence of multipartite, namely 3- or 4-partite, entangled states in a subset of the spatio-temporal modes generated by the process. These appear as bright spots against the background fluorescence, providing an interesting analogy with the phenomenology recently observed in two-dimensional nonlinear photonic crystals. We study two realistic setups: i) Non-critical phase-matching in a periodically poled Lithium Tantalate slab, characterized by a 3-mode entangled state among hot spots. ii) A type I setup in a Beta-Barium Borate crystal, where the spatial walk-off between the two pumps can be exploited to make a transition to a quadripartite entangled state. In both cases we show that the properties of the state can be controlled by modulating the relative intensity of two pump waves, making the device a versatile tool for quantum state engineering.