Data-Gouv-ML/pcri-erc-participations-et-projets-laureats huggingface dataset:
Projet ERC : HAMP-vQED (Horizon 2020, appel 2020, Advanced grants)
Domaine scientifique : Physical Sciences and Engineering
Panel : Physical and analytical chemical sciences
Entité participante : Centre national de la recherche scientifique — Pays : France — Rôle : PI
Acronyme de l'entité : CNRS
Type d'entité : Recherche
Financement ERC de l'entité : 1929658.0 €

Quantum chemical calculations are today in a position where they not only assist, but may also challenge experiment, at least for molecules containing light atoms only. When heavy atoms are present, achieving the same accuracy becomes more challenging, not only because of relativistic effects, but also because the larger number of electrons and the often complicated electronic structures make the electron correlation problem harder. When surveying the physics that has to be included in order to establish a reliable computational protocol for heavy-element chemistry, the role of quantum electrodynamics (QED) should at least be considered. Studies so far indicate that QED-effects reduce relativistic effects by about 1%. However, such investigations have been mostly limited to valence properties, since there are currently no reliable tools for general molecules to study the core region where the QED-effects are generated. The HAMP-vQED project aims to fill this gap by providing a computational machinery allowing highly accurate calculations of molecular properties, with particular focus on properties that probe electron density in the core region, such as NMR parameters. I insist on a variational approach to QED using the local, finite basis sets of quantum chemistry. In short, I want to do QED without diagrams. This allows me to verify the domain of validity of currently used effective QED-potentials and provide a more consistent formulation of relativistic quantum mechanics. QED has been called the last train from physics to chemistry. The HAMP-vQED project provides a train back to physics in the form of highly accurate calculations which, combined with experiment, will allow the exploration of nuclear structure, the standard model of the universe and beyond. An even more tantalizing perspective is that such a variational scheme to QED may inspire progress in other quantum field theories, such as quantum chromodynamics, where perturbation theory is more problematic.

Mots-clés : relativistic molecular calculations,molecular properties,quantum electrodynamics,coupled cluster theory
Projet ERC : SiMS (Horizon 2020, appel 2018, Starting grants)
Domaine scientifique : Physical Sciences and Engineering
Panel : Condensed matter physics
Entité participante : Chalmers University of Technology — Pays : Suède — Rôle : PI
Type d'entité : Enseignement supérieur ou secondaire
Financement ERC de l'entité : 1926263.0 €

Quantum computation using topologically protected Majorana bound states is a promising direction towards scalable quantum architectures due to their inherent noise immunity provided by the nonlocal storage of quantum information. Thus far, Majorana states have mostly been investigated in superconductor-semiconductor heterostructures which rely on induced superconductivity in a quasi-one-dimensional conductor. However, despite tremendous efforts in material development, these devices are still limited by uncontrolled local fluctuations due to disorder and it is unclear if future developments will solve these problems. Furthermore, disorder may even mimic the transport signatures of topological ordering, hindering an unambiguous identification of the Majorana states. Here I propose a way to overcome these limitations: I will work towards the direct quantum simulation of the one dimensional topological superconductor with Majorana bound states. I will use chains of semiconductor quantum dots, which is an emerging platform to simulate exotic many-body electron states. Building on this platform, I will be able to demonstrate for the first time the emergence of coherent, non-local superconducting states bound to the entire device similarly to the Kitaev chain model of topological superconductivity. To demonstrate quantum coherence of the chain, we will build the first Andreev molecule quantum bit, which, while not topologically protected, will already combine advantages of superconducting and semiconductor qubits. Going one step further, we will investigate the simulated Kitaev chain. Upon establishing the presence of the simulated Majorana states, we will work towards a simple braiding protocol to demonstrate the non-Abelian nature of the edge modes. This research direction, combining the scalability of semiconductor structures and the topological protection of Majorana states, will open new avenues towards universal quantum computation.

Mots-clés : superconductivity,quantum simulation,quantum dot,semiconductors,majorana states,topological states of matter
Projet ERC : QAFA (Horizon 2020, appel 2018, Consolidator grants)
Domaine scientifique : Physical Sciences and Engineering
Panel : Computer science and informatics
Entité participante : Phasecraft limited — Pays : Royaume-Uni — Rôle : Partner
Acronyme de l'entité : Phasecraft
Type d'entité : Organismes privés (hors enseignement)
Financement ERC de l'entité : 1005330.31 €

Quantum computers are designed to use quantum mechanics to go beyond the power of any standard computer based only on classical physics. Following intensive experimental efforts, it is predicted that a demonstration of so-called "quantum computational supremacy" will occur in the near future. However, many urgent questions remain regarding the usefulness of quantum computers for problems of real practical interest, and the timescale on which such usefulness will be achieved. The overall goal of this project is to address the most significant near-term and long-range theoretical challenges involved in bringing quantum algorithms to practical applications. The project comprises three programmes of work, with the following goals: - Design quantum algorithms that accelerate general classical algorithmic frameworks; develop efficient quantum communication protocols; and characterise the features of problems that allow a quantum speedup; - Demonstrate larger quantum-classical separations than previously known, and enable rigorous verification of quantum computational supremacy experiments; - Find new quantum algorithms for key problems in quantum physics, including learning and testing algorithms for large quantum systems. Simulation of quantum-mechanical systems is considered the most important application area for quantum computers, yet current algorithms are still beyond the reach of near-term devices. A unique feature of this project is its approach encompassing the full spectrum of quantum algorithms research, from underpinning mathematics through to detailed analysis of applications. Making progress on the foundations will enable progress on the more technically challenging aspects of applications, while having particular applications in mind will raise interesting new foundational questions.

Mots-clés : quantum algorithms,quantum computational complexity,theory of computation
Projet ERC : COHEGRAPH (Horizon 2020, appel 2015, Starting grants)
Domaine scientifique : Physical Sciences and Engineering
Panel : Condensed matter physics
Entité participante : Commissariat à l’énergie atomique et aux énergies alternatives — Pays : France — Rôle : PI
Acronyme de l'entité : CEA
Type d'entité : Recherche
Financement ERC de l'entité : 1500000.0 €

Quantum computing is based on the manipulation of quantum bits (qubits) to enhance the efficiency of information processing. In solid-state systems, two approaches have been explored: • static qubits, coupled to quantum buses used for manipulation and information transmission, • flying qubits which are mobile qubits propagating in quantum circuits for further manipulation. Flying qubits research led to the recent emergence of the field of electron quantum optics, where electrons play the role of photons in quantum optic like experiments. This has recently led to the development of electronic quantum interferometry as well as single electron sources. As of yet, such experiments have only been successfully implemented in semi-conductor heterostructures cooled at extremely low temperatures. Realizing electron quantum optics experiments in graphene, an inexpensive material showing a high degree of quantum coherence even at moderately low temperatures, would be a strong evidence that quantum computing in graphene is within reach. One of the most elementary building blocks necessary to perform electron quantum optics experiments is the electron beam splitter, which is the electronic analog of a beam splitter for light. However, the usual scheme for electron beam splitters in semi-conductor heterostructures is not available in graphene because of its gapless band structure. I propose a breakthrough in this direction where pn junction plays the role of electron beam splitter. This will lead to the following achievements considered as important steps towards quantum computing: • electronic Mach Zehnder interferometry used to study the quantum coherence properties of graphene, • two electrons Aharonov Bohm interferometry used to generate entangled states as an elementary quantum gate, • the implementation of on-demand electronic sources in the GHz range for graphene flying qubits.
Projet ERC : MECTRL (Horizon 2020, appel 2014, Starting grants)
Domaine scientifique : Physical Sciences and Engineering
Panel : Fundamental constituents of matter
Entité participante : Aarhus University — Pays : Danemark — Rôle : PI
Acronyme de l'entité : AU
Type d'entité : Enseignement supérieur ou secondaire
Financement ERC de l'entité : 1499406.0 €

Quantum control is an ambitious framework for steering dynamics from initial states to arbitrary desired final states. It has over the past decade been used extensively with immense success for control of low- dimensional systems in as varied fields as molecular dynamics and quantum computation. Only recently have efforts been initiated to extend this to higher-dimensional many-body systems. Most generic quantum control schemes to date, however, put quite heavy requirements on the controllability of either the system Hamiltonian or a set of measurement operators. This will in many realistic scenarios prohibit an efficient realization. Within this proposal, I will develop a new quantum control scheme, which is minimalistic on system requirements and therefore ideally suited for the efficient and reliable optimization of many-body control problems. The fundamentally new ingredient is the total quantum evolution dictated by a combination of fixed many-body time evolution and the precise knowledge of the quantum back-action due to repeated quantum non-destruction (QND) measurements of a single projection operator. The main focus of this proposal is theoretical and experimental quantum engineering of the dynamics in systems, which are sufficiently small to calculate the measurement back-action exactly and sufficiently large to have interesting many-body properties. Recent experimental advances in single site manipulation of bosons in optical lattices have enabled the high fidelity preparation exactly such mesoscopic samples of atoms (5-50). This forms an ideal starting point for many-body quantum control, and we will i.a. demonstrate engineering of quantum phase transitions and preparation of highly non-classical Schödinger cat states. Finally, using the results from an online graphical interface allowing users of the internet to solve quantum problems we will attempt to build next-generation optimization computer algorithms with a higher level of cognition built in.

Mots-clés : quantum control,non destructive quantum measurements,optical lattices,quantum engineering
Projet ERC : UniRand (Horizon 2020, appel 2020, Starting grants)
Domaine scientifique : Physical Sciences and Engineering
Panel : Fundamental constituents of matter
Entité participante : Max Planck Society — Pays : Allemagne — Rôle : PI
Acronyme de l'entité : MPG
Type d'entité : Recherche
Financement ERC de l'entité : 1497701.0 €

Quantum information theory points to new ways of classifying matter. Instead of focusing on microscopic correlation functions, it hinges on global properties of quantum states such as the presence and scaling of entanglement entropy. This general strategy relates systems of vastly different scales, for example black hole physics to information propagation in microscopic quantum systems. UniRand will realize a new, widely applicable approach to measuring global quantum state properties using ultracold atoms. At the heart of the protocol are random unitary transformations, which are applied to a quantum state before measurement. The fluctuating outcomes of measurements under random transformations encode global properties of the density matrix, including Renyi entropies and state overlaps. We are specifically interested in systems of mobile particles in optical lattices. Random unitary protocols will give access to new physics: (1) The dynamics of information scrambling as quantified by out-of-time-order correlators and (2) the order parameter-independent characterization of quantum phase transitions through measurements of fidelity. We will probe both aspects in one-and two-dimensional bosonic Hubbard systems. Our approach will be realized on a new, high-performance quantum simulator that assembles many-body systems from individually laser-cooled atoms with a high repetition rate. Protocols based on random unitaries in ultracold atom systems will open a new toolbox for system-level measurement and enable direct links between quantum information theory and experimental quantum science.

Mots-clés : optical lattices
Projet ERC : QUANTMATT (Horizon 2020, appel 2015, Starting grants)
Domaine scientifique : Physical Sciences and Engineering
Panel : Condensed matter physics
Entité participante : KTH Royal Institute of Technology — Pays : Suède — Rôle : PI
Acronyme de l'entité : KTH
Type d'entité : Enseignement supérieur ou secondaire
Financement ERC de l'entité : 1409785.37 €

Quantum matter is condensed matter which properties are dominated by the quantum nature of its constituents. The two most fundamental properties of quantum mechanics are interference and entanglement. How do these properties, and their derivatives, show up in an experiment? And how does one control them? These are the fundamental questions addressed in this proposal. The study is divided into three main parts: many-body localization, topological insulator nanowires, and topological semimetals. Many-body localization is concerned with the interplay of interference and entanglement and is central to questions about quantum thermalization. I aim to understand experimental signatures of many-body localization as well as devising simulation schemes that allow us to conduct numerical experiments on many-body localization for larger system sizes than has been so far possible. The interplay of interference, topology and geometry is the central theme of the topic of topological insulator nanowires. I have in the past theoretically demonstrated the signatures of fundamental quantum phenomena in these systems, including perfectly transmitted mode and Majorana fermions. The major goal of this part of the project is to collaborate closely with experimental groups seeking to verify my past theories, by providing new and more detailed predictions for these systems. This requires to further understand experimental details, develop certain theoretical devices and simulation techniques based on them. The final part on topological semimetals is particularly timely in view of recent experimental realizations of Dirac semimetals and the impending realization of Weyl semimetals, which both can be roughly thought of as 3D analogs of graphene. I seek to understand their unique transport signatures and the interplay of disorder with 3D Dirac fermions. The three parts feed into and from each other both through unified concepts and common methodology.
Projet ERC : MajoranasAreReal (Horizon 2020, appel 2018, Advanced grants)
Domaine scientifique : Physical Sciences and Engineering
Panel : Condensed matter physics
Entité participante : Leiden University — Pays : Pays-Bas — Rôle : PI
Type d'entité : Enseignement supérieur ou secondaire
Financement ERC de l'entité : 1952759.0 €

Quantum mechanics teaches that electrons have a complex wave function, characterized by an amplitude and a phase. As first theorized by Majorana, it is possible in principle for a charge-neutral particle to have a real wave function. Such real fermions, or Majorana fermions, could be robust carriers of quantum information, insensitive to charge noise and other sources of dephasing. With recent experimental developments in topological superconductivity this idea is becoming a reality. Our objective is to design methods to control the flow of quantum information encoded in "flying" qubits based on Majorana fermions propagating unidirectionally (chirally) in the edge modes of a topological superconductor. We aim for tools to control the phase, charge, and fermion parity of the chiral Majorana modes, on both two-dimensional and three-dimensional platforms, to enable the computational applications of entanglement, braiding, and quantum state transfer. The impact of this project is that it will provide the basic building blocks for the integration of localized and flying Majorana qubits in the architecture of a topological quantum computer. The key high-risk/high-reward deliverable is a method to exploit the chiral motion of flying Majorana qubits to facilitate braiding operations, as a demonstration of non-Abelian exchange statistics.

Mots-clés : majorana fermions,topological superconductors
Projet ERC : SEQUNET (Horizon 2020, appel 2015, Starting grants)
Domaine scientifique : Physical Sciences and Engineering
Panel : Condensed matter physics
Entité participante : RWTH Aachen University — Pays : Allemagne — Rôle : PI
Acronyme de l'entité : RWTH
Type d'entité : Enseignement supérieur ou secondaire
Financement ERC de l'entité : 1500000.0 €

Quantum networking would enable the connection of quantum processing nodes to increase computing power, long distance intrinsically secure communication, and the sharing of quantum resources over wide networks. Fully realizing these prospects requires local nodes with many coupled qubits connected by photonic links. Currently, qubits with good prospects for scaling to large numbers provide no optical interface, while optically addressable systems appear difficult to scale. This project aims to establish the fundamentals for quantum networks consisting of potentially scalable semiconductor spin qubits in gated GaAs quantum dots. These electrically controlled qubits have been proven viable for quantum computing, but so far have not been interfaced coherently with photons. To achieve the latter, we plan to use local electric fields generated by gate electrodes on both sides of a quantum well to create bound exciton states in a semiconductor structure that also hosts quantum dot qubits. These hybrid devices will make results from semiconductor quantum optics and self-assembled quantum dots applicable to gate-defined quantum dots. Besides laying the foundations for our technological goal, such a connection of two very active subfields will open a broad range of new possibilities. Building on the capability to optically address our qubits, we plan to implement a protocol to transfer their quantum state to a photon. In addition, we plan to implement exchange-based two-qubit gates for two-electron spin qubits, which promise a much higher fidelity than the demonstrated Coulomb-coupled gates. Such high fidelity entangling gates are essential for quantum information processing. We then aim to integrate a photon interface into a two-qubit device in order to entangle a photonic flying qubit and a scalable semiconductor qubit. Finally, two such devices will be used to entangle separate semiconductor qubits via a photonic link, thus demonstrating a minimal network.

Mots-clés : quantum information,semiconductor spin qubits,quantum optics,quantum communication
Projet ERC : PINQS (Horizon 2020, appel 2016, Consolidator grants)
Domaine scientifique : Physical Sciences and Engineering
Panel : Fundamental constituents of matter
Entité participante : University of Münster — Pays : Allemagne — Rôle : Partner
Acronyme de l'entité : WWU
Type d'entité : Enseignement supérieur ou secondaire
Financement ERC de l'entité : 1867312.5 €

Quantum processors are envisioned to conquer ultimate challenges in information processing and to enable simulations of complex physical processes that are intractable with classical computers. Among the various experimental approaches to implement such devices, scalable technologies are particularly promising because they allow for the realization of large numbers of quantum components in circuit form. For upscaling towards functional applications distributed systems will be needed to overcome stringent limitations in quantum control, provided that high-bandwidth quantum links can be established between the individual nodes. For this purpose the use of single photons is especially attractive due to compatibility with existing fibre-optical infrastructure. However, their use in replicable, integrated optical circuits remains largely unexplored for non-classical applications. In this project nanophotonic circuits, heterogeneously integrated with superconducting nanostructures and carbon nanotubes, will be used to realize scalable quantum photonic chips that overcome major barriers in linear quantum optics and quantum communication. By relying on electro-optomechanical and electro-optical interactions, reconfigurable single photon transceivers will be devised that can act as broadband and high bandwidth nodes in future quantum optical networks. A hybrid integration approach will allow for the realization of fully functional quantum photonic modules which are interconnected with optical fiber links. By implementing quantum wavelength division multiplexing, the communication rates between individual transceiver nodes will be boosted by orders of magnitude, thus allowing for high-speed and remote quantum information processing and quantum simulation. Further exploiting recent advances in three-dimensional distributed nanophotonics will lead to a paradigm shift in nanoscale quantum optics, providing a key step towards optical quantum computing and the quantum internet.

Mots-clés : nanophotonics,optomechanics,carbon photonics