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Novel Quantum Emitters monolithically grown on Si, Ge and III-V substrates

Periodic Reporting for period 2 - 4PHOTON (Novel Quantum Emitters monolithically grown on Si, Ge and III-V substrates)

Reporting period: 2019-01-01 to 2021-06-30

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. 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.
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 inter‐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 forged a research and training network between the leading European groups working on the next generation of solid state QIT devices based on novel photonic materials. 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. In particular, 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 unify the efforts of world-leading research and industrial EU groups in a well-structured research and training program in order to keep Europe at the highest level in the highly competitive field of nano-science and nano-technology.
In summary, 4PHOTON project pursues the following goals:
1. From the scientific and technological side to fabricate single and entangled photon sources for quantum information and quantum communication exploring innovative fabrication methods and physical properties of low dimensionality materials
2. The educational goal to provide a multidisciplinary training program for a new generation of European researchers capable to develop Quantum Technologies to the level of real-world applications.
The scientific program focused on the development of four key scientific and technological goals (KST)
KST1: Realization of on demand single and entangled photon sources relying on as-grown, droplet epitaxy, symmetric QDs
Quantum cryptography and optical computation schemes are based on the manipulation of indistinguishable and entangled photons. Fundamental understanding and consequent unprecedented control of the growth process of semiconductor quantum dots, also embedded in nanowires, has been obtained. The outcome has been the ability to fabricate GaAs quantum dots and telecom O-Band entangled photon emitters quantum photonics and quantum cryptography.
KST2: Non-classical light storage for quantum optical circuits using a deterministic single-photon sources
A quantum network consists of a coherent quantum system at each node, with each node coupled together via single photons, which must be created on demand, stored and later recreated. 4PHOTON young researchers were able to develop extremely low-noise single photon sources based on droplet epitaxy growth techniques, able to match the stringent requests for working quantum networks.
KST3: Nano-engineering of quantum confined carrier states and spin
A new class of materials, characterized by a reduced dimensionality, are now on the spot for advanced quantum technological applications. The optical and electrical properties of quantum emitters in 2D materials (e.g. MoS2) have to be widely tunable and controllable for realistic device applications. Several advances, in the understanding of fundamental properties of the excitonic emission of the mono-multilayers, also coupled to dielectric antennas, have been obtained within the project.
KST4: Fabrication of quantum integrated circuits and quantum photonic devices on silicon
An innovative path towards the integration of high efficiency quantum emitters on silicon has been studied by 4PHOTON network young researchers. It consists in the fabrication, by dewetting process, of nanoscale Mie dielectric resonators. These structures would provide self-assembled photonic cavities for the enhancement of photon extraction from quantum emitters embedded in the cavity itself.
The young researchers were trained, through research activities also performed during secondments and formal training. During the project the network organized three schools Introduction to 1- Quantum Information; 2- Quantum Dots: from growth to fundamental properties; 3- Nano Photonics and three workshops 1 - Droplet based Quantum Nanostructures and Devices; 2- Quantum Optical Devices and Circuits; 3- Quantum Optical Devices and Circuits. The final 4PHOTON conference will take place within the framework of the 8th Semiconnano web workshop.
In addition to excellent research training, ESRs received training in complementary skills through network-wide training (1- Becoming excellent and impactful communicators; 2- Collaborations across borders Quantum Communication Technology; 3- Researchers of the future) provided by Think Ahead (led by Sandrine Soubes). The ESRs YouTube videos explaining their research to non-specialists are available on the 4photon web site (
4PHOTON published 27 papers co-authored by the ESRs, all proceeding beyond the state of the art in the respective research fields and including a Nature Materials and several Nature Communications and Applied Physics Letters and Scientific Reports. The 4PHOTON outcomes were presented to around 40 international conferences.
It is possible to identify two main scientific outcomes of the 4PHOTON project. First, the knowledge developed by the project established droplet epitaxy, for the self-assembly of semiconductor quantum dots, as the leading fabrication methods, in EU as well as Japan, Korea and China, to obtain high quality single photon emitters in a wide range of wavelengths. Second, the studies conducted on the 2D materials properties as emitters and the use of Mie resonators self-assembled on Silicon to integrate single photon emitters within CMOS technology, are relevant advances that could lead to the development of innovative quantum technologies in the near future.
However, the fundamental outcome of the 4PHOTON network is the training of 15 Early Stage Researchers (with PhD degree) that will be able to contribute to the development of research in Quantum Technologies to the level of device applications. EU is strongly investing in this area, pursuing fundamental research as well as the turning of such basic finding into applications, the task that will be carried out by researchers trained within 4PHOTON and similar training initiatives.
4-Photon group photo