Spectral multiplexing of telecom emitters with stable transition frequency

TL;DR

This paper demonstrates a highly stable, spectrally multiplexed quantum emitter system at telecommunication wavelengths, achieving enhanced photon emission and coherence times suitable for quantum networks.

Contribution

It introduces a novel nanophotonic resonator setup that stabilizes erbium emitters' spectral properties, enabling multiplexed quantum communication at telecom wavelengths.

Findings

Photon emission enhanced up to 70-fold

Spectral stability < 0.2 MHz over long term

Optical coherence time of 0.11 ms

Abstract

In a quantum network, coherent emitters can be entangled over large distances using photonic channels. In solid-state devices, the required efficient light-emitter interface can be implemented by confining the light in nanophotonic structures. However, fluctuating charges and magnetic moments at the nearby interface then lead to spectral instability of the emitters. Here we avoid this limitation when enhancing the photon emission up to 70(12)-fold using a Fabry-Perot resonator with an embedded 19 micrometer thin crystalline membrane, in which we observe around 100 individual erbium emitters. In long-term measurements, they exhibit an exceptional spectral stability of < 0.2 MHz that is limited by the coupling to surrounding nuclear spins. We further implement spectrally multiplexed coherent control and find an optical coherence time of 0.11(1) ms, approaching the lifetime limit of 0.3 ms for the strongest-coupled emitters. Our results constitute an important step towards frequency-multiplexed quantum-network nodes operating directly at a telecommunication wavelength.