On-demand generation of entangled photons pairs in the telecom O-band from nanowire quantum dots

TL;DR

This paper reports the development of a high-fidelity, on-demand entangled photon pair source in the telecom O-band using site-controlled nanowire quantum dots, advancing quantum communication technologies.

Contribution

The authors demonstrate a scalable, deterministic entangled photon source in the telecom O-band with high fidelity and efficiency, expanding quantum dot applications beyond visible and NIR-I windows.

Findings

Maximum fidelity of 85.8% to Bell state

Concurrence of 75.1% achieved

Source efficiency estimated at 12.5%

Abstract

On-demand entangled photon pairs at telecom wavelengths are crucial for quantum communication, distributed quantum computing, and quantum-enhanced sensing and metrology. The O-band is particularly advantageous because of its minimal chromatic dispersion and transmission loss in optical fibers, making it well-suited for long-distance quantum networks. Site-controlled nanowire quantum dots have emerged as a promising platform for the on-demand generation of single and entangled photons, offering high extraction efficiency and the potential for scalable fabrication in large uniform arrays. However, their operation has been largely restricted to the visible and first near-infrared (NIR-I) windows. Here, we demonstrate an on-demand bright source of entangled photon pairs with high fidelity in the telecom O-band based on site-controlled nanowire quantum dots. We measure a fine-structure splitting of 4.6 $\mu$eV, verifying the suitability of the quantum dot for generating high-fidelity polarization-entangled photon pairs. Full quantum state tomography of the two-photon state generated by the biexciton\hyph exciton cascade reveals a maximum fidelity of $85.8\% \pm 1.1\%$ to the $\Phi^+$ Bell state, and a maximum concurrence of $75.1\% \pm 2.1\%$. We estimate the source efficiency at the first lens to be 12.5$\%$. This bright, scalable, and deterministic source of entangled photons in the telecom range represents a valuable step forward in advancing practical quantum applications at telecom wavelengths.