Description du sujet de thèse

This thesis is built on a deceptively simple question: what are the ultimate limits of classical physics within quantum territory?

Quantum and statistical physics appear, at first glance, to be separate kingdoms. Our goal is to map their true borderlands by aggressively extending the domain of the classical. The motivation is twofold: fundamental understanding and raw technical power. Whenever we successfully "classicalize" a quantum phenomenon, we unlock a vast arsenal of analytical and numerical tools—Monte Carlo, mean-field theory, stochastic PDEs—that can dissect the model far beyond the reach of brute-force quantum simulation. Conversely, when such a reduction fails, we have likely isolated a genuinely, irreducibly quantum feature.

Diffusive quantum transport serves as the perfect testing ground for this agenda. Diffusion typically arises from noise, disorder, or coupling to an environment—precisely the mechanisms that breed decoherence and classicality. This begs the question: Is diffusion, at its core, a classical phenomenon? If not, what are the unambiguous experimental signatures of quantum diffusion?

Depending on student interest, the thesis may also explore two further frontiers:

1) Can classical Markov processes simulate coherent quantum dynamics? A recent mapping promises exactly this, but at a strange cost: it forces the use of "negative probabilities." We will investigate whether these negative probabilities can be given a physical interpretation, or whether they represent a fundamental boundary for the classical description of quantum coherence.

2) The "rough phase" of the quantum wavefunction. Consider a quantum system subjected to frequent, strong measurements, constantly nudging it toward a classical state. Its wavefunction begins to resemble a disordered interface from statistical physics, potentially exhibiting a phase transition between a "rough" and a "smooth" regime. The role of the quantum phase in this analogy remains mysterious. We propose to explore this frontier—to understand when and how a quantum wavefunction behaves like a classical surface.

In short, this work is an exercise in boundary-testing. By seeing how much of quantum mechanics we can recast in classical terms, we hope not to diminish quantum theory, but to clarify where its true magic lies.

Contexte de travail

The position will be supervised Tony Jin https://sites.google.com/view/tonyjin/home?authuser=0 at the Nice physics institute, université Côte d'Azur and is funded by a "young researcher grant" from the French national funding agency (ANR). The expected starting date is fall 2026 but is flexible. The position comes with funding for computer hardware as well as travel funds for attending schools and conferences. There will also be opportunities for teaching.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.