Generation of Tunable Entanglement from Thin-Film Lithium Niobate

TL;DR

This paper introduces a new thin-film lithium niobate source for generating tunable polarization-entangled photon pairs at telecom wavelengths, compatible with existing fabrication technologies and capable of producing various entangled states.

Contribution

The work presents a novel lithium niobate-based entangled photon source that requires no extra optical elements and enables tunable entanglement states through crystal symmetry.

Findings

Demonstrated generation of polarization-entangled photon pairs at telecom wavelengths.

Achieved tunable entanglement states, including Bell and separable states.

Utilized the three-fold rotational symmetry of lithium niobate for state control.

Abstract

Entangled photon pairs play a major role in various modern technologies such as quantum imaging, communication, and computing. Conventional photon-pair sources are often based on spontaneous parametric down-conversion in bulk nonlinear crystals. Recent advances have also shown entangled photon-pairs from transition metal dichalcogenide thin-films, however, these materials are not widely available and are not compatible with existing fabrication capabilities. We present a new thin-film lithium niobate source of polarization-entangled photon pairs at the telecom wavelength that requires no additional optical elements for entanglement generation and allows for easy application using the existing lithium niobate fabrication technologies. We demonstrate tunable entanglement generation using the three-fold rotational crystal symmetry of lithium niobate, allowing the generation of different maximally entangled Bell states or completely separable states depending on the polarization of the pump beam.