« Information is physical » : by postulating the physical nature of information in 1961, Landauer was solving the paradox of Maxwell’s demon and successfully merging thermodynamics and information sciences. Of particular relevance is Landauer’s limit, which sets the smallest possible amount of work necessary to erase one bit of information, whereas reversibly, one bit of information can be converted into useful work (Szilard’s engine). Later in the nineties, the developments of quantum information shed novel light on entanglement, which appeared as a resource allowing to communicate more securely and to compute more efficiently than in the classical world. Recently, the peculiarities of quantum information started to be explored within a thermodynamical paradigm. Oddly enough, it was shown that the erasure of a bit could produce work provided that the observer is quantum, a drastic difference with respect to classical information. Owing to the progresses of nanotechnologies, Landauer’s limit and Szilard’s engine have recently been experimentally demonstrated with classical bits. However, thermodynamics of quantum information has remained restricted to theoretical investigations so far, involving rather abstract notions of small systems, thermal baths and batteries. The purpose of the present project is to give a physical identity to these notions, and to suggest and model experiments in this new field, in close interaction with experimental groups. Feasibility studies will be conducted for two different systems, both having already shown outstanding results in the domain of quantum information processing, namely Josephson qubits in circuit QED (case 1) and solid-state emitters in optomechanics (case 2). As a first step, we will build the conceptual and modeling tools to describe a heat engine operating at the single quantum level. We will particularly focus on extensively characterizing the work produced by the machine, that will either consist of tiny electromagnetic (case 1) or phononic fields (case 2). This is drastically new with respect to former estimations of the thermodynamical quantities, so far based solely on measurements performed on the small working system itself. This approach relies on the ability to monitor continuously such environments as transmission lines or phononic fields, an ability that we plan here to exploit for the first time in a thermodynamical context. This study should lead to the first direct measurement of Landauer’s limit. As a second step, we will study the potential of each system as a platform to investigate new physical effects related to quantum information and entanglement. In this perspective, heat engines involving two quantum bits will be modeled. In particular, we will explore to which extent the useful energy extracted from the engine can be used to quantify the strength of the correlations between the two qubits. A final product of these fundamental investigations could be a heat engine working as entanglement witness. The success of the present project will contribute to create an important synergy between a wide range of scientific communities : quantum optics, quantum information, thermodynamics, circuit QED and optomechanics. It will benefit from the collaboration with a high level team working on theoretical aspects of the thermodynamics of quantum information, and aims at developping a local think tank around these groundbreaking ideas, in direct connection with experimentalists. From a deeper point of view, this project will bring out the first building blocks for the comprehension of information/energy conversion at the nanoscale, a fundamental issue in our society of information.

Devices based on the control of quantum states will revolutionize information and communications technologies. It is now possible to fabricate and isolate individual quantum objects that can be prepared in any superposition of quantum states. Several implementations of the quantum bit (Qubit), i.e. the building block for systems targeting quantum-enabled functionalities, were already demonstrated. Approaches based on all-superconducting materials provide the most advanced solid-state platform to date but one of their drawbacks is that they must rely on magnetic effects for control and operation, which is not an industry standard for devices. This starts already to be an issue in large scale circuits. On the other hand, approaches fully based on semiconductors provide spin Qubits with long coherence times that are electrically tunable and addressable. They are very promising for large scale integration because they are based on mainstream industry technologies. But fast quantum state readout will require their co-integration with superconducting resonators. To bridge the gap between these two approaches, I propose the integration of a gapless two-dimensional semiconductor, graphene, in the key element of superconducting quantum circuits: the Josephson junction, a weak link between two superconducting electrodes. It will create an electrically tunable Josephson element. The resulting quantum circuits will gain electrical tunability, a breakthrough for control and future integration. Assisted by a strong theoretical support, several pivotal elements of quantum technologies will be demonstrated during the project: an electrically tunable Qubit, an electrically pumped quantum limited Josephson parametric amplifier and an electrically controlled coupler between Qubits that will be a major step for future scaling. Beyond those demonstrations, the unique properties of a graphene based Josephson element will be used to build a topologically protected Qubit, i.e. a Qubit that is intrinsically immune to decoherence, an outstanding problem in quantum computation. Graphene, which can now be grown on wafer scale while maintaining high electron mobilities, is only one atom thick and can be combined in a simple manner with mainstream technologies by using recently developed transfer techniques. This is a fundamental asset for future developments and a clear advantage compared to competing technologies based on III-V semiconductor nanowires or two-dimensional electron gas.

Quantum theory is certainly one of the most successful theories, and has so far never been contradicted by any experiment. However, a clear understanding of its foundations is still missing; the intriguing question of why the world follows such puzzling rules as those of quantum theory is, after a hundred years, still begging for an answer. Recent progress on quantum foundations has nevertheless been made possible by the emergence of quantum information. By revolutionizing the way we perceive and manipulate information, this young and very dynamic field of research has already led to a vast number of significant results, and to the development of important applications and technological advances, with a great impact on society. Quantum information has also brought major insights on quantum foundations, and has a great potential to lead to even more discoveries. This project makes the most of these prospects. Specifically, we will revisit one of the fundamental concepts of quantum theory, namely the celebrated Heisenberg uncertainty principle, with an innovative approach and new techniques developed in the field of quantum information. One implication of the uncertainty principle is the concept of complementarity, which says that some properties of a quantum system—like for instance the location and speed of a particle—are incompatible and cannot be measured at the same time. It is however still possible to approximate a joint measurement of both properties, and gain some partial information on each of them. We will quantify precisely the optimal trade-off between the information one can obtain on each incompatible property. Although this is a very natural way of presenting the uncertainty principle and the concept of complementarity, such trade-offs have yet never been properly analysed. Determining the amount of information obtainable through a measurement will allow us to reconsider the very limits imposed by quantum theory, and will shed a new light on its foundations. To gain more insights, we will question how much of quantum theory can be reconstructed from the concept of complementarity, taken as a fundamental axiom, and which other axioms are necessary to fully reconstruct the theory. This will give clues on why Nature chose quantum theory among other possible theories, and will offer an original perspective to the quest of the Holy Grail of quantum foundations, namely the derivation of quantum theory from more physical axioms than its standard ad hoc ones. In addition to this specific research programme, our objective is also to launch a new research activity and establish quantum foundations as a full-fledged research domain at the Institut Néel. The Institute hosts a number of world-class experimental groups already conducting experiments in quantum information, whose know-how could directly benefit quantum foundations. This project aims at establishing a think tank to stimulate new ideas and create a fruitful synergy between our expertise in quantum foundations and the experimental capabilities already present at the Institut Néel. This will lead to the realisation of exciting and significant thought experiments testing the foundations of quantum theory, questioning our interpretations of the theory, and challenging our best understanding of the physical world.

This project is focused on the correlation of Transmission Electron Microscopy (TEM) based techniques with optical and electrical characterization on the same unique semi conductor nanowire (NW). Robust sample preparation methods will be developed to perform such correlated measurements routinely and perform in-situ biasing experiments in the TEM. Furthermore the TEM sample holder that allows such measurements will be improved, either by further development of a home-made sample holder, or by acquisition of a commercial holder. The new holder should also permit cooling of the specimen to allow transport measurements in the TEM. The aim is to study the effect of nm scale structural and chemical properties of the NW on the electrical and optical properties. The nm scale properties that could be studied involve the crystalline phase and growth direction, the presence of crystallographic defects, the surface roughness or facets, the analysis of heterostructures regarding the interface abruptness and chemical composition, the doping concentration and interface abruptness in a p-n junction and the properties and interface of metal contacts on the nanowire (NW). This projects aims to combine competences in TEM, optics and electron transport in a single person, being M.I. den Hertog, the Project Initiator (PI), and her future research group. This is possible because of the unique environment in the Grenoble area where leading experts are present in the field of nanowire growth, TEM, optics and transport on NWs. The PI has strong competences in TEM based techniques and can gather competences in optics and electron transport through collaborations with scientists working in various groups at the Institut Néel and CEA Grenoble. In the fist stage of the project different approaches will be developed for sample preparation suitable for correlated measurements. In the second stage of the project these different approaches will be tested on GaN - AlN NW heterostructures to correlate optical and transport characteristics with TEM characterization on the same single NW. In a third stage of the project the electrical contacts applied to the NWs will also be used to bias the NW in-situ in the microscope. One goal is to propagate a semiconductor metal phase into a silicon NW and actively design the source, drain and channel length of a transistor with atomic resolution. Furthermore the contacts could allow quantitative dopant characterization using electron holography by in-situ reverse biasing of the junction.

Catalysis is one of the most effective and economic technologies to control air pollution problems. Catalysts reduce pollution by facilitating the conversion of a harmful pollutant to a less-harmful material. The catalysis business is also a growing market in the energy and environmental segments. However, the key issue is the availability of industry-relevant high-performance technical catalysts. The technical catalysts are relatively large multicomponent bodies in which the research catalysts, the small active laboratory-developed catalytic materials, are distributed within their porous microstructure. Despite the tremendous importance in industry, the understanding of the complex structure-property-function of technical catalysts is largely neglected, and the main focus of academic research is still the research catalysts. This is due mainly to industry secrecy and to limitations of the state-of-the-art characterization techniques. To revert this scenario, ASTeCa will develop a novel 3D hyperspectral non-destructive nanoimaging technology capable to simultaneously provide the morphology of the internal microstructure of technical catalysts, the mass density distribution of each sample components, and the chemical information of the catalyst's contaminants or additives. This will be implemented based on a combination of X-ray ptychography, spectroscopic methods and computed tomography. The project objectives are to: develop two 3D hyperspectral nanoimaging modalities, which are (1) the high-resolution 3D resonant ptychographic imaging, and (2) the X-ray near-edge structure ptychographic imaging; (3) implement an innovative 3D reconstruction method for thick samples of catalysts; validate the proposed methodology by (4) application to industry-relevant technical catalysts. In contrast to the classical XAS methods or microscopy methods, this new technology will allow us to correlate for the first time the catalysis activity and morphology of the technical catalyst, at multiple length scales, and to distinguish the different regions within the sample. ASTeCa will deliver an innovative characterization methodology that will assist the design and optimization of technical catalysts that can potentially solve major challenges in energy production and reduction of pollution-related global warming. The anticipated achievements will bring laboratory developments much closer to industry.