Polarization entangled state measurement on a chip

TL;DR

This paper demonstrates an integrated photonic device capable of measuring polarization-entangled states on a chip, advancing quantum optics integration with femtosecond laser waveguide technology.

Contribution

It introduces a femtosecond laser written directional coupler supporting polarization qubits and demonstrates quantum interference and entanglement measurement on a chip.

Findings

Successful quantum interference with polarization entangled states

Support for arbitrary polarization states in waveguide device

Effective singlet state projection on a chip

Abstract

The emerging strategy to overcome the limitations of bulk quantum optics consists of taking advantage of the robustness and compactness achievable by the integrated waveguide technology. Here we report the realization of a directional coupler, fabricated by femtosecond laser waveguide writing, acting as an integrated beam splitter able to support polarization encoded qubits. This maskless and single step technique allows to realize circular transverse waveguide profiles able to support the propagation of Gaussian modes with any polarization state. Using this device, we demonstrate the quantum interference with polarization entangled states and singlet state projection.