Research

The Mpemba effect, where a system initially farther from equilibrium relaxes faster than one closer to equilibrium, has been extensively studied in classical systems and recently explored in quantum settings. While previous studies of the quantum Mpemba effect (QME) have largely focused on isolated systems with global symmetries, we argue that the QME is ubiquitous in generic, non-integrable many-body systems lacking such symmetries, including U(1) charge conservation, spatial symmetries, and even energy conservation. Using paradigmatic models such as the quantum Ising model with transverse and longitudinal fields, we show that the QME can be understood through the energy density of initial states and their inverse participation ratio in the energy eigenbasis. Our findings provide a unified framework for the QME, linking it with classical thermal relaxation and phenomena such as prethermalization and weak ergodicity breaking.

Here is a poster about this work: Poster

The quantum description of a black hole predicts that quantum information hidden behind the event horizon can be teleported outside almost instantaneously. In this work, we demonstrate that a chiral spin-chain model, which naturally simulates a binary black hole system, can realise this teleportation process. Our system captures two essential components of this protocol: Hawking radiation, which generates the necessary entanglement between the black holes, and optimal scrambling, which enables high-fidelity teleportation on short timescales. Through numerical simulations, we quantify the key timescales governing the process, including the Page time, radiation time, scrambling time, and butterfly velocity, showing their universal dependence on the chiral coupling strength. Our results establish the feasibility of simulating quantum properties of black holes within condensed matter systems, offering an experimentally accessible platform for probing otherwise inaccessible high-energy phenomena.

Lattice gauge theories, the discretized cousins of continuum gauge theories, have become an important platform for the exploration of non-equilibrium phenomena beyond their original scope in the Standard Model. In particular, recent works have reported the possibility of disorder-free localization in the lattice Schwinger model. Using degenerate perturbation theory and numerical simulations based on exact diagonalization and matrix product states, we perform a detailed characterization of thermalization breakdown in the Schwinger model including its spectral properties, the structure of eigenstates, and out-of-equilibrium quench dynamics. We scrutinize the strong-coupling limit of the model, in which an intriguing, double-logarithmic-in-time, growth of entanglement was previously proposed from the initial vacuum state. We identify the origin of this ultraslow growth of entanglement as due to an approximate Hilbert space fragmentation and the emergence of a dynamical constraint on particle hopping, which gives rise to sharp jumps in the entanglement entropy dynamics within individual background charge sectors. Based on the statistics of jump times, we argue that the entanglement growth, averaged over charge sectors, is more naturally explained as either single-logarithmic or a weak power law in time. Our results thus suggest the existence of a single ergodicity-breaking regime due to Hilbert space fragmentation, whose properties are reminiscent of conventional many-body localization within the numerically accessible system sizes.

Here is a poster about this work: Poster 

Generic quantum systems thermalize as entanglement builds up between a subsystem and its complement. Performing measurements on a complementary subsystem, however, can reveal finer nuances in the system’s ability to thermalize. We show here that systems that look ‘thermal’ under the lens of the Eigenstate Thermalization Hypothesis (ETH) can be highly ‘nonthermal’ when probed deeper. We illustrate this finding on several constrained models that describe slow relaxation in quantum glasses and quantum many-body scars in Rydberg atom arrays.

Here is a poster about this work: Poster

We investigate the effect of band geometric quantities on nonlinear magnetoresistivity, which dictates the quadratic dependence of the nonlinear voltage generated by the applied current. We propose that the interplay of the Berry curvature, the orbital magnetic moment, and the Lorentz force can induce a finite nonlinear resistivity in two-dimensional systems in the presence of a perpendicular magnetic field. The induced nonlinear magnetoresistivity scales linearly with the magnetic field and is purely quantum mechanical in origin. Our proposed transport signature can be used as an additional experimental probe for the geometric quantities in intrinsically time reversal symmetric systems.

I worked with Dr. Tommaso Roscilde (ENS de Lyon) to study the dynamics of entanglement generation in a Rydberg atom system. The aim was to study entanglement witnesses made from global and experimentally accesible observables. This was followed by a study of the thermalization (or it's lack thereof) of the system, revealing a breakdown of the Eigenstate Thermalization Hypothesis, which was mapped across the phase diagram of this system.

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