Research project QUANCOM

Doctoral training

QUANCOM is a competitive Doctoral Training Unit (DTU) supported by the research funding scheme PRIDE of the Luxembourg National Research Fund (FNR).

Doctoral projects

Multiscale modeling in materials science and physics

The overarching goal of the QUANCOM DTU is to develop fundamental theories for the description of dynamics and measurement in realistic many-body quantum systems, developing ab-initio tools to model dynamical dispersion forces and better understand decoherence process, from the microscopic to the macroscopic limit. Understanding the complexity of quantum dynamics will be the basis to develop quantum algorithms for quantum optimization.

For this, 8 doctoral candidates will develop a research project on theory, computation, and experimental quantum physics, as detailed in the doctoral projects.

As a whole, this programme aims to further our understanding of fundamental phenomena defining dynamical material functions and push the development of materials and algorithms for quantum technologies.

QUANCOM DTU Coordinator: Aurélia Chenu (DPhyMS).

The aim of the doctoral project is to go beyond the Gaussian description of the environment and derive a description of the open dynamics through a master equation at all coupling strengths, which can interpolate between the Forster and Redfield limits. This will be done by finding the basis that is physically relevant to capture the system and treat perturbatively the rest. In particular, we will focus on non-Markovian effects and systems coupled to a structured environment. The latter will be first modeled with colored noise, which is an extension of the methods currently being developed in the QDC group.

Supervised by A. Chenu in collaboration with M. Esposito and A. del Campo.

How to apply

Send your CV and a motivation letter to:

We will use group theory (more specifically permutation invariance) to provide dynamical and thermodynamic descriptions of open quantum systems in the thermodynamic limit. This would generalize to quantum systems’ recent work on the macroscopic limit of stochastic thermodynamics. This will be used to better characterize the role of quantum effects in nonequilibrium phase transitions and of nonequilibrium dispersive forces.

Supervised by M. Esposito in collaboration with A. del Campo and A. Tkatchenko.

How to apply

Send your CV and a motivation letter to:

This project targets the quantum dynamics of nuclei in condensed matter, taking into account non-adiabatic effects together with the influence of long-range (including van der Walls and Casimir dispersion) interactions, with their pairwise and many-body description. Modern experiments and corresponding industrial applications require theoretical tools accounting for non-adiabatic effects—beyond the Born-Oppenheimer (BO) approximation. We will consider the three general cases: (i) molecules on the surface of condensed matter, where the approach developed for molecular systems can be directly applied; (ii) dynamics of defects within condensed matter, which treatment is close to that of molecular systems but requires involving an environment; (iii) dynamics of nuclei within crystal lattices, including its phonon description (again including non-adiabatic effect in the corresponding equation of motion for such quasiparticles).

Supervised by A. Tkatchenko in collaboration with T. Schmidt and A. Chenu

How to apply

Send your CV and a motivation letter to:

Optical excitations and their coherent quantum dynamics play a key role for many quantum-technologies. These excitations can take place at specific defect sites in wide band gap semiconductors (e.g., hexagonal boron nitride) hexagonal boron nitride (where they have been shown to be potential single-photon emitters). Or they take place in the form of strongly bound excitons, e.g., in 2D materials where excitonic effects are particularly pronounced. Accurate calculation methods for the time-development of these excitations are still in their infancy. Exact exciton-phonon coupling needs to be calculated to understand luminescence lineshapes and decoherence phenomena. Building upon our previous works, we will develop time-dependent many-body perturbation theory to follow the excitation of materials with a specifically shaped laser pulse in real time. We will take into account the coupling to a “phonon bath” and thus gain information about decoherence processes. Our simulations will accompany the experimental work of PhD7.

Supervised by L. Wirtz in collaboration with D. Brida

How to apply

Send your CV and a motivation letter to:

This theory project will focus on semiclassical and quantum dynamics in materials with topologically nontrivial band structures. Regarding materials, we will focus on two-dimensional materials, e.g., van der Waals heterostructures of transition metal dichalcogenides as well as graphene-like systems with induced spin-orbit coupling. These systems offer interesting condensed-matter analogs to relativistic systems because the low-energy electron dispersion relations are identical to those of relativistic fermions. In particular, we aim to study how slow space- and time-dependent perturbations, generated by electric and magnetic fields as well as strains and temperature gradients, can be described using general relativistic models with curved spacetimes. Since some of these perturbations give rise to “tilted” Dirac spectra in materials, the resulting nontrivial electron dynamics can allow one to design “tiltronics” devices, where position- and time-dependent tilts can be used to steer an electron current. In this project, we will further study this topic by starting the investigation from the semiclassical dynamics of wave packets and proceeding to a fully quantum mechanical description.

Supervised by T. Schmidt in collaboration with A. Tkatchenko and L. Wirtz.

How to apply

Send your CV and a motivation letter to:

Salient applications of quantum computing are focused on quantum optimization, for use cases such as portfolio optimization and protein folding. The latter are under exhaustive investigation worldwide using variational quantum algorithms, that reduce such problems of industrial and societal interest, to finding low-energy configurations of a given problem Hamiltonian. Recent research has shown that heuristic quantum algorithms for quantum optimization such as the Quantum Approximate Optimization Algorithm (QAOA) can be improved in combination with techniques developed in the context of Shortcuts To Adiabaticity, aimed at speeding up the dynamics of quantum systems. The application of these techniques to many-body systems has been pioneered by the PI. In particular, accumulated evidence indicates that variational quantum algorithms can be improved by the use of Digitized counter-diabatic driving to enhance the operator pool of the ansatz used in the underlying parameterized quantum circuit. Such algorithms still rely on classical optimizers for their implementation. However, the need for the latter is not necessary and can be removed. The thesis aims at developing a new class of quantum algorithms for quantum optimization using the counterdiabatic driving with Krylov subspace methods.

Supervised by A. del Campo in collaboration with A. Tkatchenko, and P. Ryan and P. Roenne at SnT.

How to apply

Send your CV and a motivation letter to:

By illuminating matter with extremely short pulses of light it becomes possible to observe the dynamics induced by photon absorption at the level of the fundamental quantum interactions and at the temporal scale at which they occur. In this context, the doctoral student will employ advanced techniques that make use of a multi-pulse approach to access several temporal and frequency dimensions for the observation of quantum interactions in materials like 2D chalcogenides. It will be possible to investigate how excitons, phonons, carriers and spins interact in complex band-structure landscapes. The main samples for the experimental studies will be layered semiconductors and heterostructures where the excitation leads to dynamical phenomena connected to quantum many-body interactions. The interest to perform these experiments lays on the potential use of these novel materials for quantum technology applications. The project finds a natural interaction with the theoretical description and modeling of time-domain phenomena in complex systems.

Supervised by D. Brida in collaboration with L. Wirtz and A. Tkatchenko DB.

How to apply

Send your CV and a motivation letter to:

Truly quantum behaviour can be witnessed by correlation functions that are non-Gaussian, i.e. that have no classical equivalence. Current theories of quantum measurement are based on Glauber theory, which has been successful to shed light into the relations between the classical and quantum theories of light. We aim to extend the theory of quantum measurement for strongly interacting systems, in order to quantitatively describe how strong or long-range interactions affect observables and correlation functions. This will be looked for using field-theory, based on experimentally accessible correlators. We consider the use of quantum trajectory methods, to unravel for parameter estimation including the effect of quantum measurement. This formalism can lead to the development of protocols to control quantum matter using feedback.

Supervised by A. Chenu in collaboration with A. del Campo, A. Tkatchenko.

How to apply

Send your CV and a motivation letter to:

Career development

Training and career development

The QUANCOM doctoral candidates will be trained as quantum physicists with a very solid foundation of condensed matter physics, especially in (i) ab-initio calculations, (ii) quantum optics and quantum information and (iii) statistical mechanics with a specific strength in understanding nonequilibrium quantum properties in different models (integrable, chaotic, low-dimensional, molecular) across the different time scales. The training will be structured among 3 pillars: i) doctoral school training, mainly for transferable skills, ii) DTU in-house tailored training and career development, and iii) DTU tailored training by external partners.

Doctoral schools and doctoral program

The doctoral candidates in the DTU will be enrolled into the Doctoral School in Science and Engineer (DSSE). The DSSE offers 7 programs including the Physics and Material Sciences (DPPM). The program offers specialized modules in disciplinary training, interdisciplinary training and transferable skills, detailed in the table below. The DTU training program will be included in the course program with the corresponding ECTS.

QUANCOM training

Our training strategy aims to provide doctoral candidates with a solid foundation of theory and experiments. In addition to the individual research project, the candidates will have the opportunity to exchange through weekly quantum forums to encourage discussion on the research questions, challenges and approaches. This weekly meeting will gather the QUANCOM doctoral candidates, who will start with a 5-min round table each on their weekly updates, and 1 PI of the DTU (rotating each week). The follow-up discussion will revolve around lectures and workshops featuring prominent experts throughout the duration of the DTU program. A retreat will be held annually for all PIs and doctoral candidates.

Training of multifaceted physicists

The training programme aims to build a framework for the quantum-smart workforce through rigorous training on fundamental theory (non-adiabatic dynamics, quantum transport, control techniques, nonequilibrium phase transition, complexity
of quantum dynamics), computational tools (ab-initial calculations, machine learning, many-body perturbation theory, large deviation techniques, path integral, random matrices theory, etc), and experience on an optical setup (ultrafast laser pulses). The common courses will form the students in modern physics; in addition, a second-phase training will offer demand-driven courses which are tailored to skills needed by the group of students. These will be identified from the weekly meetings and discussed in the midterm retreat before being implemented.

Career development

Luxembourg offers a unique environment for doctoral students to grow as researchers. UniLu offers transferable skills, including career development, lecturing and teaching, proposal writing, presentation and communication skills, project management, academic best practices, open science, IP management, as well as entrepreneurship training. FNR, Luxinnovation and Research Luxembourg offer workshops on grant writing, events for science communication, training on spin-offs and business skills and various opportunities to engage in public outreach (Chercheurs à l’école, Scicom events, etc.). There are also mentor programs for researchers, such as ADVANCE. QUANCOM’s goal is to build competent and resilient researchers who bridge the gap across different physics disciplines, constituting a cohort of solid, creative physicists capable of shaping the second quantum revolution.

Doctoral courses

  • Aim & workload

    Number of ECTS: 1
    In-person course workload (hrs): 12
    Homework workload (hrs): 8

    Introduction of the tools to describe the dynamics of quantum systems interacting with an environment.

  • Organiser

    AC, ME

  • Aim & workload

    Number of ECTS: 1
    In-person course workload (hrs): 15
    Homework workload (hrs): 10

    This course will give an introduction to quantum optics: quantization of the electromagnetic field,
    quantum states of light and their representation, atom-field interaction, cavity QED, Jaynes-Cummings model, squeezed light, optical master equation.

  • Organiser

    AC + group

  • Aim & workload

    Number of ECTS: 1
    In-person course workload (hrs): 10
    Homework workload (hrs): 6

    Introduction to the different hardwares for quantum platforms, including SC qubits, topological qubits, colored centers.

  • Organiser

    AdC, DB, AC

  • Aim & workload

    Number of ECTS: 1
    In-person course workload (hrs): 15
    Homework workload (hrs): 10

    This course will introduce the basics of quantum computation and information and its intersection with cryptography. It includes presenting the positive aspect of quantum computation in cryptographic applications (such as quantum key distribution protocols) and presenting the negative aspect of quantum computation to classical cryptographic constructions due to period finding quantum algorithms (Shor’s algorithm).

  • Organiser

    AdC, ME, SnT

  • Aim & workload

    Number of ECTS: 1
    In-person course workload (hrs): 15
    Homework workload (hrs): 10

    Foundations of the statistical approach to quantum mechanics first for closed systems: full counting statistics, laws of thermodynamics, fluctuation theorems, Jarzynski equality for closed quantum systems, and then for open systems using master equations and path integral approaches (Redfield equation, Keldysh contour techniques). Applications to quantum optics.

  • Organiser

    ME group

  • Aim & workload

    Number of ECTS: 1
    In-person course workload (hrs): 15
    Homework workload (hrs): 10

    Path integrals for fermionic and bosonic fields, field theoretical approaches for quantum Hall systems and superconductors (Chern-Simons theory, Ginzburg-Landau theory), topological field theory.

  • Organiser

    TS

  • Aim & workload

    Number of ECTS: 1
    In-person course workload (hrs): 15
    Homework workload (hrs): 10

    The content of the course includes the description of the fundamental concepts necessaries to observe phenomena at the femtosecond scale and beyond. The course will introduce the experimental techniques and what can be observed in experiments.

  • Organiser

    DB