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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - 4PHOTON (Novel Quantum Emitters monolithically grown on Si, Ge and III-V substrates)

Teaser

Summary

4PHOTON addresses the major disruptive technology of the near future: the Quantum Information Technology (QIT). 4PHOTON outcomes directly impact on the viability of QIT by providing fundamental know-how and trained researchers to this expanding field. The researcher profile required by QIT is extremely multi-specialized, being required to tackle problems in fundamental quantum physics, optics, photonics and device fabrication (growth and processing). Thus interâ€disciplinary and intersectoral training of ESRs is needed for the future development of the technology, with strong interlink between academia and business. Three main targets are considered fundamental, by industries active in the field, to pave the way to a successful impact of QIT on industry and society: (1) Nurture new skills and roles; (2) Expand quantum computing education programs; (3) Increase open innovation between academia and business. With these goals in mind, 4PHOTON will forge a research and training network between the leading European groups working on the next generation of solid state QIT devices based on novel materials for photonics. It is a vast and novel research area that lies at the crossroads of photonics, material science, quantum physics and nano-scale device fabrication. It combines challenges in the fabrication and understanding of efficient quantum emitters with tailored properties, in the development of new scientific equipment enabling advanced experiments and devices at the single/multiple quantum level. Very recent technological, experimental and theoretical breakthroughs, many by members of 4PHOTON, have demonstrated potential for rapid progress in this field.

Work performed

During the period of 01/01/2017 to 31/12/2018 fifteen ESRs have been recruited and enrolled in PhD courses. The School â€œIntroduction to Quantum Informationâ€ was organized in Basel in February 2018 and the Workshop â€œQuantum Optical Devices and Circuitsâ€ was organized in Eindhoven in September 2018. Think Ahead has implemented the Training Needs Analysis and Career Development Plans in collaboration with all the ESRs. All the ESRs have been trained about health/safety procedures.
Seven ESRs were involved in the different tasks related to the growth of quantum. In particular the fabrication of quantum dots of GaAs and InAs by droplet epitaxy, by droplet etching and by the insertion of a quantum dot in a nanowire has been studied to obtain single and entangled photon emitters and structures suitable for quantum memory applications. Different photonic cavities and resonators were studied and integration tests were performed. Monolithic integration of quantum nanostructures capable of single photon emission on Silicon and Germanium substrate were also studied with different approaches: quantum emitter embedded in AlGaAs deposited on Ge islands fabricated by dewetting and quantum dots embedded in nanowires fabricated directly on Si substrate.
Nine ESRs worked on the characterization of the samples and on the theory development. These activities were focused on having a feedback to develop improved samples for single and entangled photon emitters. Optical characterizations were performed to measure the linewidth and the fine structure splitting of the quantum dots and to prove the quantum properties of the emitted photons. Light emission was measured and characterized by micro photolminescence for quantum emitters embedded in AlGaAs grown on Ge island. Hanbury-Brown and Twiss , time resolved photoluminescence and entanglement experiments were performed on InAsP quantum dots embedded in InP nanowire waveguides. From the theoretical side, theory to better understand single photon devices and to improve their design is under development. A study about the modeling of the shape of GaAs quantum dots to achieve more realistic structures were performed to understand the effect of shape anisotropy on the fine structure splitting. Theoretical calculations of optical properties, anisotropy of electronic magnetic moments, excitonic properties of localized states and strong coupling of electron and nuclear spins through hyperfine interaction in quantum dots were also performed.
Eight ESRs worked on the development of devices and applications. By investigating and optimizing the device design and the experimental parameters, it was possible to embed droplet epitaxy quantum dots inside a light emitting diode capable of electrical generation of entangled photon pairs on demand. A resulting entanglement fidelity of up to 84% was measured. Investigations on GaAs nanobeam photonic crystal cavities were also performed in order to characterize the properties of quantum dots by using a fast superconducting nanowire single photon detector.

Final results

The main motivation of 4PHOTON is to train young researchers for better career perspectives in QIT in the European Research Area (ERA). ERA needs a creative, adaptable, diverse and networked workforce with the right balance of skills to ensure it benefits from new opportunities in quantum technologies. As a matter of fact, a shortage of skills is no small challenge for any new technology adoption and QIT will not be an exception. Once the technical and economic challenges of quantum computers are overcome, the third greatest obstacle will be finding people to design, build, manage and operate these new machines. Entirely new roles will emerge around necessary skill sets, not only variations of quantum scientists and engineers, but also managers and even entrepreneurs. The 4PHOTON extensive network will provide the starting key point for future employability in QIT of the young researchers through their significant exposure to a truly multi-national, multidisciplinary and inter-sectoral environment in QIT related Key Enabling Technologies (KETs).
As a matter of fact, QIT is an area of cutting-edge scientific research that has the potential to deliver huge benefits for the European economy. 4PHOTON research area is on the development and application of opto-electronic based QIT. The quantum techniques used by 4PHOTON partners provide an innovative approach which allow responding to current demands from industry. Based on the recent progress in quantum photonic devices achieved due to the work of the network beneficiaries in this domain, 4PHOTON target is to unify efforts of world-leading research and industrial EU groups in a well-structured research and training programme in order to keep Europe at the highest level in the highly competitive field of nano-science and nano-technology. 4PHOTON will thus facilitate future research and training excellence within the ERA by: (i) increasing research group sizes of consortium beneficiaries; (ii) increasing interactions with colleagues and improved working relationships between participants; (iii) providing an effective research platform to effectively deal with competitors in Asia and the USA; (iv) spreading best practice and strengthening individual teams from different disciplines, sectors, and countries; (v) building improved training programs, seminar series and conferences, which will further promote excellence of the individual teams; (vi) providing strong support for new funding for applied and fundamental research training; (vii) profiling these institutions as attractive working places for other researchers and particularly young scientists.