Nanopost cavity device emits high-quality photons on demand with widely tunable bandwidth

Photonic structures that extract light from quantum dots over a broad range of wavelengths are key features for scaling up optical quantum technologies. Nanopost cavities have shown promise because of their wide operational bandwidth, efficient extraction, and ability to enhance the quantum dot (QD)’s spontaneous emission rate.

Gaignard et al. have developed a nanopost device that emits indistinguishable single photons on demand. It uses a self-assembled quantum dot embedded in a nanoscale Fabry-Pérot optical resonator built with a short segment of photonic wire, closed by a bottom gold mirror and a flat-top facet mirror. The resulting device’s quasi-resonant laser pulse features demonstrate its ability to cleanly emit high-quality photons that are quantum-mechanically identical, or indistinguishable, on demand.

“This is the first time a QD in a nanopost is excited with quasi-resonant laser pulses and is shown to emit indistinguishable photons,” said author Julien Claudon. “With further improvements, we anticipate that QDs in nanoposts will play a key role in the development of advanced sources of quantum light for photonic quantum technologies, such as broadly tunable single-photon sources, sources of entangled photon pairs, and other sources of multiphoton entangled states.”

Most QD single-photon sources involve microcavities with high quality factors, which accelerate the QD’s spontaneous emission but over a narrow operational bandwidth.

By measuring intensity fluctuations between detectors, the group found their device exhibited excellent single-photon purity, deviating from the ideal value by 2.3%. Two-photon quantum interference measurements between consecutive photons showed a wavepacket overlap of 46%, which defines a new state-of-the-art value among single-photon sources built with nanowires.

The group is working on the next generation of nanopost-based devices, aiming to demonstrate a widely-tunable source emitting identical single photons.

Source: “Indistinguishable single photons from a quantum dot in a nanopost cavity,” by Maxime Gaignard, Lorenzo De Santis, Mackrine Nahra, Saptarshi Kotal, Alberto Artioli, Yann Genuist, Niels Gregersen, Jean-Michel Gérard, Jean-Philippe Poizat, and Julien Claudon, APL Quantum (2026). The article can be accessed at https://doi.org/10.1063/5.0336317 .

This paper is part of the Quantum Nanophotonics Collection, learn more here .