A Quantum Dot Source of On-Demand Entangled Photons for Space-Based Quantum Networking

Icarus Quantum, the University of Illinois Urbana-Champaign (UIUC), and the National Institute of Standards and Technology (NIST) propose to build the most efficient entangled photon source with high entanglement fidelity. This source is based on GaAs quantum dots (QDs) that can generate entangled photons at drastically higher rates than other products in the market, enabling satellite-based quantum networking.  During Phase I, our team successfully grew these dots in pristine conditions using Molecular Beam Epitaxy. We also designed and fabricated the building blocks of a QD-based entanglement generator: deterministic charge control structures and optical cavities. We measured the QD emission at a single-photon level, achieving emission wavelengths at 780 nm within 10 nm, a 1.4 MHz emission rate without cavities, and a purity of 0.992. In addition, we proposed a novel scheme to generate post-selected entangled photons with efficiencies up to 50% by using a QD as a single-photon source and entangling two consecutively emitted photons with a linear optical circuit. In Phase II, we will integrate all the pieces demonstrated individually in Phase I to build an efficient entangled-photon source suitable for space-based quantum communications. We will finalize our growth parameters and charge control circuits, and embed QDs in optical cavities fabricated by our team, to build an entangled photon generator with efficiencies > 10% and entanglement fidelities > 0.9. We will also demonstrate our post-selected scheme in an intermediate step as a landmark for the quantum communications field. We will demonstrate single-device entanglement swapping and heralded entanglement generation, showing the "swappability" of our photons as a preliminary step to interface multiple devices in Phase III. Finally, we will deliver our efficient entanglement generator device to AFRL/RDSS and work with the Starfire Optical Range (SOR) team to test our devices in AFRL facilities. Our team consists of industry (Icarus), academia (UIUC), and a national lab (NIST). Icarus is the only US-based quantum company that develops QD technologies. Icarus has demonstrated success in prototyping a QD-based single-photon source. Icarus is a spinout of the Quantum Nanophotonics Group at NIST Boulder, which has more than two decades of experience in growing high-quality QDs and fabricating structures around them. Finally, we are partnering with the Kwiat Group at UIUC, the academic leader in space-based quantum networking in the United States. Our interdisciplinary team has all the expertise on both device and system levels needed to successfully accomplish the tasks proposed in this Phase II project. The results of this project are the only solution for scaling quantum networks in rates and range, enabling even intercontinental entanglement distribution and secure quantum communications.