Generation of modal and path-entangled photons using a domain-engineered integrated optical waveguide device

TL;DR

This paper presents a novel integrated optical waveguide device that generates highly entangled photon pairs with modal and path entanglement, advancing quantum information and metrology applications.

Contribution

It introduces a domain-engineered lithium niobate waveguide scheme for simultaneous phase matching of two SPDC processes, enabling generation of complex entangled states.

Findings

Achieves near-maximal entanglement over a wide parameter range

Produces a NOON state for N=2 in the degenerate case

Potential for generating hyperentangled and multipath-entangled states

Abstract

Integrated optical devices are expected to play a promising role in the field of quantum information science and technology. In this paper, we propose a scheme for the generation of nondegenerate, copolarised, modal, and path- entangled photons using a directional coupler and an asymmetric Y-coupler geometry in type 0 phase-matched domain engineered lithium niobate(LN) waveguide. The nonlinearity in LN is tailored in such a way that quasi phase matching conditions for two different spontaneous parametric down conversion processes are obeyed simultaneously, leading to a modal and path-entangled state at the output. Assuming typical values of various parameters, we show, through numerical simulations, that an almost maximally entangled state is achievable over a wide range of waveguide parameters. For the degenerate case, the scheme gives a NOON state for N = 2. The generated entangled photon pairs should have potential applications in quantum information schemes and also in quantum metrology. By appropriate domain engineering and component designing, the idea can be further extended to generate hyperentangled and two-photon multipath-entangled states, which may have further applications in quantum computation protocols.