Site-controlled quantum dot arrays edge-coupled to integrated silicon nitride waveguides and devices

TL;DR

This paper demonstrates the deterministic integration of site-controlled quantum dots with silicon nitride waveguides, enabling scalable quantum photonic circuits with high-yield, reproducible single-photon sources at cryogenic temperatures.

Contribution

It introduces a method for active alignment and edge-coupling of site-controlled quantum dots to silicon nitride waveguides, improving scalability and integration in quantum photonics.

Findings

Achieved high-yield, regular arrays of single-photon sources.

Observed spectral overlap of adjacent quantum dot emitters.

Coupling efficiencies of approximately 5% between quantum dots and waveguides.

Abstract

The scalability of quantum photonic integrated circuits opens the path towards large-scale quantum computing and communication. To date, this scalability has been limited by the stochastic nature of the quantum light sources. Moreover, hybrid integration of different platforms will likely be necessary to combine state-of-the-art devices into a functioning architecture. Here, we demonstrate the active alignment and edge-coupling of arrays of ten site-controlled gallium arsenide quantum dots to an array of ten silicon nitride single-mode waveguides, at cryogenic temperatures. The coupling is facilitated by the fabrication of nanopillars, deterministically self-aligned around each quantum dot, leading to a high-yield and regular array of single-photon sources. An on-chip beamsplitter verifies the triggered emission of single photons into the silicon nitride chip. The low inhomogeneous broadening of the ensemble enables us to observe the spectral overlap of adjacent site-controlled emitters. Across the array of waveguides, the signal collected from each coupled quantum dot is consistently and reproducibly 0.17 relative to the free-space collection from the very same single-photon source. Comparing measurement with waveguide simulations, we infer that absolute coupling efficiencies of $\approx 5 \%$ are currently obtained between our quantum dots and the waveguides.