Thesis and Dissertation Defenses
Entanglement with neutral atoms in the simulation of nonequilibrium dynamics of one-dimensional spin models
Presented by Anupam Mitra
In this dissertation, we study the generation and role of entanglement in the dynamics of many-body spin-1/2 models, both for design of quantum gates for general purpose quantum computation and for quantum simulation of interacting spin models. We introduce the neutral atom Mølmer-Sørensen gate involving rapid adiabatic Rydberg dressing passages interleaved in a spin-echo sequence, for entanglement generation. We show that the adiabatic Rydberg dressing paradigm leads to a robust gate which can be extended to regimes beyond the Rydberg blockade and can achieve the fundamental bounds of entanglement generation for neutral atoms using interactions between Rydberg states. The findings provide a path towards Rydberg mediated entanglement between neutral atoms in future experiments in large arrays of atoms, and sufficient laser power to harness the interactions between Rydberg states. In the context of quantum simulation, we consider critical behavior in quench dynamics near a dynamical quantum phase transition in transverse field Ising models. Using matrix product states to calculate the dynamics, we find that not only the order parameters, but also the critical point and critical exponents can be estimated using modest bond-dimension. We also relate the approximation of local observables to chaos and equilibration in the quench being studied, finding that local observables are well approximated either due to low entanglement in the global wavefunction or the proximity of local marginal states to the maximally mixed state. These findings highlight the challenge of identifying relevant quantum phenomena that remain inaccessible to classical descriptions. Chaotic evolution, while making classical simulation of the exact many-body state intractable at long times and large system sizes, scrambles information and makes macro-properties more amenable to classical simulation.
4:00 pm, Wednesday, March 27, 2024
PAIS-2540, PAIS
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