Experimental characterization of photonic fusion using fiber sources

TL;DR

This paper demonstrates fiber-based photon fusion to generate polarization entangled states, analyzing the process's efficiency and imperfections, and providing a model for practical quantum photonic applications.

Contribution

It presents the first experimental fiber-based photon fusion with detailed process characterization and a model explaining entanglement generation and imperfections.

Findings

Achieved up to 0.74 fidelity with Bell state

Success rates increased to 111.6 four-folds/sec at higher pump power

Developed a model fitting experimental results and explaining imperfections

Abstract

We report the fusion of photons from two independent photonic crystal fiber sources into polarization entangled states using a fiber-based polarizing beam splitter. We achieve fidelities of up to F = 0.74 $\pm$ 0.01 with respect to the maximally entangled Bell state \phi+ using a low pump power of 5.3mW with a success rate of 3.2 four-fold detections per second. By increasing the pump power we find that success rates of up to 111.6 four-folds per second can be achieved, with entanglement still present in the fused state. We characterize the fusion operation by providing a full quantum process reconstruction. Here a model is developed to describe the generation of entanglement, including the main causes of imperfection, and we show that this model fits well with the experimental results. Our work shows how non-ideal settings limit the success of the fusion, providing useful information about the practical requirements for an operation that may be used to build large entangled states in bulk and on-chip quantum photonic waveguides.