arXiv subjects

Chaitali Shah

Publications and source records attributed to Chaitali Shah.

4 recordsLinked to original sources

arXiv2026

Quantum Correlations in Frustrated Three-Body Systems

Many physical systems are not understood from first principles due to the presence of multi-body quantum correlations. The effort taken to simulate such systems on classical computers increases exponentially with increase in the system size. We study simple, yet non-trivial, three-body frustrated systems that can help in understanding the underlying quantum correlations. First we investigate the ground state of helium-like atoms using the variational method and physically meaningful ansatze, revealing how quantum entanglement arises due to frustration in the system. Next we consider another frustrated three-body system, the hydrogen molecular ion, and analytically demonstrate the nature of its wavefunction arising from the quantum tunneling phenomenon. Finally, we extend these results to model yet another physically important system, the hydrogen bond.

quant-ph↗

arXiv2026

Tunable Mpemba Effect in a Prethermal Many-Body Spin Network

Relaxation in an interacting system is determined not only by its initial distance from equilibrium, but also by the relaxation modes populated by the initial state. Here we experimentally observe and control the Mpemba effect, in which a state farther from equilibrium overtakes one initially closer, in an extended, disordered $^{13}$C nuclear-spin network in diamond. Field cycling allows us to prepare distinct spatial polarization profiles by independently controlling hyperpolarization and defect-mediated relaxation. We then track their evolution under Floquet driving, which stabilizes a long-lived prethermal regime. We observe reproducible Mpemba crossings and tune the crossing time over several orders of magnitude, from late-time thermalization into the prethermal plateau. Semiclassical simulations show that randomly positioned paramagnetic defects create fast-relaxing regions and defect-poor regions that support the slowest collective relaxation mode. The Mpemba crossings are set by the initial state overlap with this mode. Our results demonstrate anomalous relaxation within a prethermal many-body regime and identify disorder, transport, and mode-selective state preparation as resources for controlling relaxation in extended spin networks.

quant-ph↗

arXiv2026

Breakdown of Disorder-Suppressed Floquet Heating under Two-Frequency Driving

Periodic (Floquet) driving enables Hamiltonian engineering and nonequilibrium phases, but interacting systems eventually heat by absorbing energy from the drive. Disorder can greatly delay this process, yielding long-lived prethermal plateaus. Here we show that this protection can fail when pulse-train control introduces a second driving frequency and when the disorder fluctuates. Using a natural-abundance 13C nuclear-spin network in diamond, we observe sharp peaks in the late-time heating rate at the double- and triple-spin-flip resonance conditions predicted by bimodal Floquet interference, and track their evolution with drive frequency. A switching-noise model attributes the resonant absorption to stochastic electron-spin dynamics that intermittently tune rare nuclear clusters into multi-photon resonance. Our results reveal a resonance-activated limit for disorder-stabilized Floquet phases and suggest new routes to DC-field quantum sensing based on an abrupt breakdown of prethermalization.

quant-ph↗

arXiv2025

Emergent Decoherence Dynamics in Doubly Disordered Spin Networks

Elucidating the emergence of irreversible macroscopic laws from reversible quantum many-body dynamics is a question of broad importance across all quantum science. Many-body decoherence plays a key role in this transition, yet connecting microscopic dynamics to emergent macroscopic behavior remains challenging. Here, in a doubly disordered electron-nuclear spin network, we uncover an emergent decoherence law for nuclear polarization, $e^{-\sqrt{R_{p}t}}e^{-R_{d}t}$, that is robust across broad parameter regimes. We trace its microscopic origins to two interdependent decoherence channels: long-range interactions mediated by the electron network and spin transport within the nuclear network exhibiting anomalous, sub-diffusive dynamics. We demonstrate the capacity to control--and even eliminate--either channel individually through a combination of Floquet engineering and (optical) environment modulation. We find that disorder, typically viewed as detrimental, here proves protective, generating isolated electron-free clusters that localize polarization and prolong coherence lifetimes. These findings establish a microscopic framework for manipulating decoherence pathways and suggests engineered disorder as a new design principle for realizing long-lived quantum memories and sensors.

quant-ph↗