Polarization-entangled Bell state generation from an epsilon-near-zero metasurface

Area of Science:

• Quantum optics and photonics
• Materials science and nanotechnology

Background:

• Polarization-entangled photons are crucial for quantum technologies like communication, computation, and imaging.
• Generating complex entangled states is limited by natural material nonlinearities, requiring complex setups.
• Existing methods often need additional coherent superposition or postselection steps.

Purpose of the Study:

• To demonstrate a new method for generating polarization-entangled photon pairs.
• To utilize a plasmonic metasurface coupled with an epsilon-near-zero (ENZ) material for enhanced photon generation.
• To achieve direct control over quantum states in a compact platform.

Main Methods:

• Experimentally demonstrated photon pair generation using a plasmonic metasurface strongly coupled to an ENZ material.
• Engineered a resonance at the pump wavelength to leverage ENZ field enhancement.
• Utilized the metasurface's engineered anisotropic second-order nonlinear susceptibility for state manipulation.

Main Results:

• Achieved a substantial boost in photon pair generation efficiency compared to unpatterned films.
• Successfully generated polarization-entangled photon pairs, including a Bell state, without extra components.
• Demonstrated versatile manipulation of the nonlinear susceptibility tensor for quantum state control.

Conclusions:

• The ENZ metasurface platform offers a compact and efficient solution for generating polarization-entangled photons.
• This approach simplifies the generation of complex quantum states, overcoming limitations of natural materials.
• Enables simultaneous photon pair generation and quantum state engineering, advancing quantum technology development.