Hi, I'm Stefan Aimet.

About

After completing a BSc in Theoretical Physics and MSc in Quantum Fields and Fundamental Forces at Imperial College London, I have embarked on an exciting journey as a PhD student with Prof. Jens Eisert at the Dahlem Center for Complex Quantum Systems, Freie Universität Berlin. In my PhD, I work on a project on realising genuine quantum thermal machines with ultracold quantum gases giving rise to quantum fields. You can reach me at stefan.aimet@fu-berlin.de.

My research interests are in Quantum Thermodynamics, Quantum Information and Many-body physics.

Papers

Engineering a heat engine purely driven by quantum coherence

The question of whether quantum coherence is a resource beneficial or detrimental to the performance of quantum heat engines has been thoroughly studied but remains undecided. To isolate the contribution of coherence, we analyze the performance of a purely coherence-driven quantum heat engine, a device that does not include any heat flow during the thermodynamic cycle. The engine is powered by the coherence of a multiqubit system, where each qubit is charged via interaction with a coherence bath using the Jaynes-Cummings model. We demonstrate that optimal coherence charging and hence extractable work is achieved when the coherence bath has an intermediate degree of coherence. In our model, the extractable work is maximized when four copies of the charged qubits are used. Meanwhile, the efficiency of the engine, given by the extractable work per input coherence flow, is optimized by avoiding the coherence being stored in the system-bath correlations that is inaccessible to work. We numerically find that the highest efficiency is obtained for slightly lower temperatures and weaker system-bath coupling than those for optimal coherence charging.


Gravity mediated entanglement between light beams as a table-top test of quantum gravity 

Over the past century, a large community within theoretical physics has been seeking a unified framework for quantum gravity. Yet, to date, there is still no experimental evidence of any non-classical features of gravity. While traditional experimental proposals would usually require immensely challenging Planck scale experiments, recent table-top protocols based on lowenergy quantum control have opened a new avenue into the investigation of non-classical gravity. An approach that has sparked high interest, both in terms of experimental feasibility and of theoretical implications, is the indirect witnessing of non-classical gravity through the detection of its capacity to act as an entangling channel. Most discussions have been centred on the entanglement generation between two gravitationally coupled massive systems. In this work, we instead examine the entangling capacity of the gravitational interaction between two light pulses, we explain the main experimental and theoretical advantages of having a photonic protocol, and lay out the steps leading to the determination of the entangling phase, using the path integral formalism and linearised gravity. We establish a closed form formula for the entangling phase and provide an estimated order of magnitude of the average photon number required for the generation of appreciable phase. 

Experimentally probing Landauer's principle in the quantum many-body regime 

Landauer’s principle bridges information theory and thermodynamics by linking the entropy change of a system during a process to the average energy dissipated to its environment. Although typically discussed in the context of erasing a single bit of information, Landauer’s principle can be generalized to characterize irreversibility in out-of-equilibrium processes, such as those involving complex quantum many-body systems. Specifically, the relation between the entropy change of a system and the energy dissipated to its environment can be decomposed into changes in quantum mutual information and a difference in the relative entropies of the environment. Here, we experimentally probe Landauer’s principle in the quantum many-body regime using a quantum field simulator of ultracold Bose gases. Employing a dynamical tomographic reconstruction scheme, we track the temporal evolution of the quantum field following a global mass quench from a massive to a massless Klein–Gordon model and analyse the thermodynamic and information-theoretic contributions to a generalized entropy production for various system–environment partitions of the composite system. Our results verify the quantum field theoretical calculations, interpreted using a semi-classical quasiparticle picture. Our work demonstrates the ability of ultracold atom-based quantum field simulators to experimentally investigate quantum thermodynamics.

For a full list of my publications, see my Google Scholar profile.