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arXiv:1903.10074 · Physical Review A

Zero supermode-based multipartite entanglement in χ(2) nonlinear waveguide arrays

David Barral, Kamel Bencheikh, Nadia Belabas, Juan Ariel Levenson

Published May 7, 2019• 11 citations
arXivHTMLPDF

Abstract

We show that arrays of ${\ensuremath{\chi}}^{(2)}$ nonlinear waveguides in the second-harmonic generation regime are a promising source of continuous-variable entanglement. We indeed demonstrate analytically that optical arrays with an odd number of waveguides injected with the zero-eigenvalue fundamental supermode entangle this fundamental supermode with a collective harmonic field. Moreover, the fundamental individual modes are multipartite entangled and their entanglement grows with propagation length. The device is scalable, robust to losses, does not rely on specific values of nonlinearity and coupling, and is easily realized with current technology. It thus stands as an unprecedented candidate for generation of multipartite continuous-variable entanglement for optical quantum information processing.

DOI
10.1103/physreva.99.051801

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We show that arrays of \ensuremathχ(2){\ensuremath{\chi}}^{(2)}\ensuremathχ(2) nonlinear waveguides in the second-harmonic generation regime are a promising source of continuous-variable entanglement. We indeed demonstrate analytically that optical arrays with an odd number of waveguides injected with the zero-eigenvalue fundamental supermode entangle this fundamental supermode with a collective harmonic field. Moreover, the fundamental individual modes are multipartite entangled and their entanglement grows with propagation length. The device is scalable, robust to losses, does not rely on specific values of nonlinearity and coupling, and is easily realized with current technology. It thus stands as an unprecedented candidate for generation of multipartite continuous-variable entanglement for optical quantum information processing.
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Multimode entanglement is an essential resource for quantum networks. Continuous-variable encoding of quantum information in the optical domain has recently yielded large temporal and spectral entangled states instrumental for quantum computing and quantum communication. We introduce a protocol for the generation of spatial multipartite entanglement in a monolithic photonic device: the array of quadratic nonlinear waveguides. We theoretically demonstrate the generation of large multipartite entangled states in the spontaneous parametric downconversion regime. Our protocol is remarkably simple and robust as it does not rely on specific values of coupling, nonlinearity or length of the sample.
We study a class of nonlinear waveguide arrays in which the waveguides are endowed with ${\ensuremath{\chi}}^{(2)}$ nonlinearity and coupled through the evanescent overlap of the guided modes. We investigate the viability of such an array as a platform for generating both bipartite and tripartite continuous-variable entanglement. We explicitly address the effect of realistic losses on the entanglement produced, discuss the possible types of nonlinear materials that could be used, and suggest solutions for the possible phase matching issues in the waveguides. The simultaneous generation and manipulation of the light on a single waveguide chip circumvents the usual bandwidth problems associated with the use of external bulky optical elements and makes this avenue promising for further investigation.