[Paper Review] Polarization-entangled photon pair generation from an epsilon-near-zero metasurface

Wenhe Jia, Grégoire Saerens+6 more|arXiv (Cornell University)|May 6, 2024

Metamaterials and Metasurfaces Applications5 citations

TL;DR

The paper demonstrates a nanoscale source of polarization-entangled photon pairs using a plasmonic metasurface coupled to an epsilon-near-zero material, enabling direct Bell-state generation without extra components.

ABSTRACT

Polarization-entangled photon pair sources are essential for diverse quantum technologies, such as quantum communication, computation, and imaging. However, the generation of complex polarization-entangled quantum states has long been constrained by the available nonlinear susceptibility tensor of natural nonlinear crystals, necessitating a cumbersome and intricate setup for additional coherent superposition or post-selection. In this study, we introduce and experimentally demonstrate a nanoscale polarization-entangled photon pair source utilizing an artificially-engineered metamaterial platform. This platform is based on a plasmonic metasurface that is strongly coupled to an epsilon-near-zero (ENZ) material. By precisely engineering resonances at both pump and signal/idler wavelengths, and leveraging the field enhancement provided by the ENZ effect, the photon pair generation efficiency of the 68-nm-thick metasurface is significantly boosted. More notably, the ENZ metasurface platform facilitates versatile manipulation of the system's anisotropic second-order nonlinear susceptibility tensor, enabling direct control over the polarization states of the photon pairs, which leads to the generation of a polarization-entangled Bell state without the need for additional components. Our approach opens a new avenue for the simultaneous photon pair generation and quantum state engineering in a compact platform.

Motivation & Objective

• Motivate the need for compact, integrated polarization-entangled photon sources for quantum technologies.
• Propose a metamaterial platform that combines plasmonic metasurfaces with epsilon-near-zero materials to enhance nonlinear generation.
• Show experimentally that the ENZ metasurface enables direct generation of polarization-entangled photon pairs without post-selection or additional optics.

Proposed method

• Engineer a plasmonic metasurface strongly coupled to an ENZ material to enhance field strengths at pump and signal/idler wavelengths.
• Tune resonances at pump and signal/idler wavelengths to boost photon-pair generation via nonlinear processes.
• Exploit the anisotropic second-order nonlinear susceptibility tensor to manipulate polarization states and generate entanglement.
• Demonstrate generation of a polarization-entangled Bell state directly from the metasurface without auxiliary components.

Experimental results

Research questions

• RQ1 Can an ENZ-assisted metasurface directly generate polarization-entangled photon pairs without post-selection or extra optical elements?
• RQ2 How does the engineered anisotropic second-order nonlinear susceptibility tensor enable control over Bell-state generation?
• RQ3 What is the impact of metasurface thickness and resonance tuning on photon-pair generation efficiency?

Key findings

• A 68-nm-thick metasurface enables polarization-entangled photon-pair generation.
• The ENZ metasurface allows direct control over the polarization states to produce a Bell state without additional components.
• Resonances at pump and signal/idler wavelengths are engineered to enhance nonlinear generation through field amplification.
• The platform demonstrates simultaneous photon-pair generation and quantum state engineering in a compact form factor.