Detection of single ions in a nanoparticle coupled to a fiber cavity

TL;DR

This paper demonstrates the detection of single erbium ions in nanoparticles within a tunable fiber cavity, advancing quantum hardware for long-distance quantum communication by enabling efficient single-photon emission at telecom wavelengths.

Contribution

It introduces a fully fiber-integrated, tunable cavity system for detecting single solid-state ions, with enhanced emission and interaction potential at nanometer scales.

Findings

Detection of individual spectral features with saturation behavior

Uncorrected g^{(2)}(0) of 0.24 confirms single emitter presence

Ions confined in a volume two orders of magnitude smaller than previous work

Abstract

Many quantum information protocols require the storage and manipulation of information over long times, and its exchange between nodes of a quantum network across long distances. Implementing these protocols requires an advanced quantum hardware, featuring, for example, a register of long-lived and interacting qubits with an efficient optical interface in the telecommunication band. Here we present the Purcell-enhanced detection of single solid-state ions in erbium-doped nanoparticles placed in a fiber cavity, emitting photons at 1536 nm. The open-access design of the cavity allows for complete tunability both in space and frequency, selecting individual particles and ions. The ions are confined in a volume two orders of magnitude smaller than in previous realizations, increasing the probability of finding ions separated only by a few nanometers which could then interact. We report the detection of individual spectral features presenting saturation of the emission count rate and linewidth, as expected for two-level systems. We also report an uncorrected $g^{(2)} \left ( 0 \right )$ of 0.24(5) for the emitted field, confirming the presence of a single emitter. Our fully fiber-integrated system is an important step towards the realization of the initially envisioned quantum hardware.