Terahertz research has undergone breakthroughs over the past 20 years, both for fundamental science and industrial applications. Despite extremely promising applications, THz radiation is still a challenging spectral domain in need of technological and conceptual advances. The main aim of the HYPSTER proposal is to investigate innovative 3D lens-less techniques, to extract amplitude and phase information, with performances well beyond the current state-of-the-art in real time. To this end, we will transfer to the THz range, wavefront concepts and tools developed in the optical domain. Potential applications range from non-destructive testing of plastics, composites, electronic devices, and ceramics up to the biomedical field. To do so, the objectives of the HYPSTER project are to perform multispectral THz holography and ptychographic imaging systems to improve phase retrieval and surpass the resolution limit. We will use state of the art real-time camera illuminated by a high power multispectral QCL source. The proposal aims to create and understand 3D diffractive imaging thanks to the leadership of 2 academic experienced research institutes gathered in an interdisciplinary and complementary consortium. The success of the research program relies on shared experience at a high level of specialization from these well-established internationally renowned laboratories.

In PhotonicQRC we will implement a disruptive photonic quantum reservoir computer for the first time. Quantum reservoir computing combines novel machine learning with quantum physics: a complex, un-optimized coherent quantum state (the reservoir) is linearly transformed to emulate a target quantum system. The key advantage is that the exponentially scaling dimensionality of quantum physics can be exploited under relaxed, hence more hardware friendly conditions. Based on the unique expertise of the 4 partners, we will experimentally demonstrate networks of >10 electrically-tuned semiconductor quantum dots (TUB) coherently coupled via integrated photonic waveguides using the latest 3D additive fabrication (FEMTO-ST). Comprehensive theoretical investigations on the required coherence-level (Uni Bremen) will be experimentally confirmed based on demonstrated entangled photon sources (SU). PhotonicQRC will investigate fundamental questions and realize a first of its kind quantum computer.

We propose to design, fabricate and measure a new hybrid qubit that combine bosonic and fermionic degrees of freedom in order to realize more robust quantum states.

The goal of the project is to study the potential of optical semiconductor microcavities as THz detectors and emitters. We propose here to explore the possibility of detecting and generating THz radiation in semiconductor microcavities by using THz radiative transitions between polaritonic states. Polariton physics is now well known and especially well mastered by the three project partners (LKB, LPA, LPN). The investigated polariton states are separated in energy by typically a few meV (i.e. in the THz range). If the THz radiative transitions between the polariton branches are normally forbidden by the selection rules, different theoretical proposals open the way for engineering the band structure to allow the absorption or radiative emission of THz photons. A particularly interesting aspect of this project lies in using the peculiar properties of polaritons to avoid the low temperature constraint usually required by thermodynamics principles. The objective of the project is the realization of THz detectors operating at liquid nitrogen temperature with high detectivity in compact geometries, compatible with the development of semiconductor based devices. Conversely and in similar schemes, we will study the potential of such semiconductor microcavities for THz emission by using the bosonic stimulation regime (polariton lasing).. Different strategies proposed by the theory to allow THz radiative transitions will be implemented in the design and fabrication of a new family of semiconductor microcavities and micropillars. These structures will then be studied in the field of optics and THz using methods controlled by three partners: - LPA brings its expertise and experimental facilities in the field of THz spectroscopy, optical spectroscopy and theory - LKB brings its expertise and experimental facilities in the optical study of polaritons under "two-photon" and non-linear excitation of the polariton states - LPN provides expertise on the sample fabrication as well as its expertise on polariton lasers.

Over the past decade, the field of quantum computing has become a major driving force for both fundamental physics and engineering, with impressive milestones demonstrated on several competing platforms. But today, even for an expert in the field, it is still hazardous to predict which physical system will be the most successful implementation in 10 years’ time, because achieving large-scale universal operations on a quantum computer requires not only world-class engineering, but also major conceptual breakthroughs. Optical quantum computers, and in particular nanophotonic circuits, are among the leading candidates due to their high scalability and small footprint. However, implementing universal operations on scalable nanophotonic platforms requires deterministic nonlinearities at the single-photon level, and so far, no known approach has been able to implement it reliably. The CoCoON project proposes to solve this critical problem by using quantum nano-emitters efficiently coupled to a nanophotonic waveguide, a nanofiber, to mediate deterministic nonlinear interactions between photonic qubits. With its original approach, the project bridges the gap between nanophotonics (usually limited to the discrete-variable approach) and the continuous-variable regime, through the generation of non-gaussian states. In doing so, I will answer fundamental questions about the amount of nonlinearity and quantumness contained in the light-matter interaction described by the Jaynes Cummings model, and that is required to achieve scalable universal photonic quantum computing.