Indistinguishable deterministic quantum dots for quantum networking

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Microelectronics; Quantum Science; Space Technology; Advanced Materials OBJECTIVE: This topic seeks to develop a scalable technology for single photon sources that demonstrates indistinguishability between various single photon sources allowing a interference between the various Quantum Dot emitters in integrated photonic circuits. DESCRIPTION: In this topic, epitaxial quantum dots will be produced and characterized to determine the statistics associated with the fabrication process. This include parameters such as emission wavelength, lifetime and purity. Ideally, these single photon emitters should be coupled to a photonic cavity which will demonstrate full, on-chip entanglement of distinct sources and generate the correlation matrix for the process as well as determine the visibility of the entanglement. All this information should be used to assess problems in the scale up of this technology to large number of single photon sources. Using the epitaxial quantum dots, efforts to assess ability to align single-photon-emitters to other structures (waveguides, optical cavities for Purcell enhancement, etc.) are essential for scalable quantum photonic networks. PHASE I: This topic is intended for mobile robotic manipulator technology proven ready to move directly into a Phase II. Therefore, a Phase I award is not required. The offeror is required to provide detail and documentation in the Direct-to-Phase-II proposal which demonstrates accomplishment of a Phase I-like effort, including a feasibility study. This topic is intended to scale recent demonstrations in mesa-topped single-quantum-dot emitters or droplet-formed epitaxial quantum dots, which show order-of-magnitude improvements to spectral emission uniformity across a wafer. Traditional self-assembled epitaxial quantum dots are stochastically created, which causes a variety of quantum dot sizes across the wafer. The spectral behavior is determined by the quantum dot geometry, which causes large differences in spectral emission between disparate quantum dots (greater than 30 nanometer), thus inhibiting entanglement between them. However recent progress using the aforementioned techniques have dramatically reduced the size uniformity such that the emission from the quantum dots are very similar (often less than 1nanometer) across large areas of the semiconductor wafer). These smaller spectral differences are well within typical tuning techniques such as thermal- and Stark-tuning. Therefore proposers should be able to demonstrate their ability to generate uniform emission across many quantum dots. PHASE II: Eligibility for D2P2 is predicated on the offeror having performed a Phase I-like effort predominantly separate from the SBIR Programs. Under the phase II effort, the offeror shall sufficiently develop the technical approach, product, or process in order to conduct a small number of relevant demonstrations. Identification of manufacturing/production issues and or business model modifications required to further improve product or process relevance to improved sustainment costs, availability, or safety, should be documented. These Phase II awards are intended to provide a path to commercialization, not the final step for the proposed solution. The effort should: 1. Demonstrate Molecular Beam Epitaxy (MBE) growth of Quantum Dots with p-i-n junctions, demonstrating emission linewidths less than 800 Megahertz. 2 Optical Cavity Fabrication: Forming a top-down cavity and characterization of the optical cavity and demonstrating a quality factor greater than 10,000. 3 Quantum Dot-Cavity Integration: Embed MBE-grown Quantum Dots inside optical cavities with tunability. 4 Single-Photon Generation (a) Measuring a single-photon rate greater than 10 Megahertz. (b) Measuring a single-photon purity greater than 0.99. 5 Entanglement Generation (a) Measuring a photon pair rate > 10 Megahertz. (b) Measuring entanglement fidelity greater than 0.9. 6 Integration into Air Force Facilities: Ship a device to the Air Force generate and measure entanglement at Air Force facilities. 7 Reporting: Comply with reporting requirements of the Air Force. PHASE III DUAL USE APPLICATIONS: The contractor will pursue commercialization of the various technologies developed in Phase II for transitioning expanded mission capability to DARPA QuanNEt and AFRL Information Directorate, as well as a broad range of potential government and civilian users and alternate mission applications. Direct access with end users and government customers will be provided with opportunities to receive Phase III awards for providing the government additional research & development, or direct procurement of products and services developed in coordination with the program. REFERENCES: 1. J. Vac. Sci. Technol. B 32, 02C106 (2014), https://doi.org/10.1116/1.4863680 2. Yang et al. Light: Science & Applications (2024)13:33, https://doi.org/10.1038/s41377-024-01384-7 3. Optics Express Vol. 24, Issue 26, pp. 29955-29962 (2016), https://doi.org/10.1364/OE.24.029955 KEYWORDS: single photon source; quantum network; entanglement distribution; epitaxial quantum dot