Dynamics of Interacting Atoms in Optical Lattices

Ultracold atoms in optical lattices offer a powerful platform for quantum simulation of interacting many-body systems. Canonical spin and Hubbard-type models can be faithfully realized thanks to the clean environment and long coherence times offered by the platform. Optical lattices also have access to external tools such as laser driving, which enable augmentation or tuneability of the realized systems. In this thesis, we explore the utility of such tools for realizing more tuneable systems, and for applications such as entanglement generation. We first study the use of spin-orbit coupling, generated by driving the atoms with lasers, to tune the dynamics of an optical lattice loaded with fermionic atoms with two flavors in the Mott insulating limit. The conventional antiferromagnetic superexchange interactions between the atoms are shown to be dressed by the laser, generating a more complex spin-1/2 XXZ model that can be controlled by the drive strength and spin-orbit coupling phase. This model is shown to be useful for generating cluster states for measurement-based quantum computation, which leverage the parallel nature of the atomic interactions to front-load entanglement generation. We also consider the use of the model for spin-squeezing, which can enable quantum-enhanced metrology by generating an entangled state before performing measurements. Going beyond spin physics, we study a resonant regime where atoms can move in the insulating limit due to the interplay between tunneling, spin-orbit coupling and interactions. We show that an effective kinetically constrained picture emerges, derive effective rules for the atomic motion, and demonstrate interesting self-binding properties that the atoms exhibit. We also show that the system can be used to emulate a synthetic magnetic field piercing a lattice. The response of this system to this effective field is described using the kinetic constraints. An analogous model for atoms with more than two internal levels is also derived, and the resonant response to the field is characterized. Aside from spin-orbit coupling, we also consider the use of excited band states to further control atomic dynamics. We first show that such band states can be used to robustly encode quantum information in a decoherence-free subspace insensitive to external noise. We then discuss the utility of excited bands for accessing p-wave interactions. An explicit scheme for measuring both on-site and cross-site interactions is provided. An experiment that successfully measures the on-site portion is also discussed.</p

Estimating non-flow effects in measurements of directed flow of protons with the HADES experiment at GSI

Centrality dependence of the directed flow of protons in Au+Au collisions at the beam energy of 1.23A GeV collected by the HADES experiment at GSI is presented. Measurements are performed with respect to the spectators plane estimated using the Forward Wall hodoscope. Biases due to non-flow correlations and correlated detector effects are evaluated. The corresponding systematic uncertainties are quantified using estimates of the spectators plane from various forward rapidity regions constructed from groups of Forward Wall channels and protons reconstructed with the HADES tracking system.Comment: Proceedong for the LXX International conference "NUCLEUS - 2020. Nuclear physics and elementary particle physics. Nuclear physics technologies

Spin squeezing in mixed-dimensional anisotropic lattice models

We describe a theoretical scheme for generating scalable spin squeezing with nearest-neighbour interactions between spin-1/2 particles in a 3D lattice, which are naturally present in state-of-the-art 3D optical lattice clocks. We propose to use strong isotropic Heisenberg interactions within individual planes of the lattice, forcing the constituent spin-1/2s to behave as large collective spins. These large spins are then coupled with XXZ anisotropic interactions along a third direction of the lattice. This system can be realized via superexchange interactions in a 3D optical lattice subject to an external linear potential, such as gravity, and in the presence of spin-orbit coupling (SOC) to generate spin anisotropic interactions. We show there is a wide range of parameters in this setting where the spin squeezing improves with increasing system size even in the presence of holes.Comment: 13+9 pages, 8+1 figure

Quantum computation toolbox for decoherence-free qubits using multi-band alkali atoms

We introduce protocols for designing and manipulating qubits with ultracold alkali atoms in 3D optical lattices. These qubits are formed from two-atom spin superposition states that create a decoherence-free subspace immune to stray magnetic fields, dramatically improving coherence times while still enjoying the single-site addressability and Feshbach resonance control of state-of-the-art alkali atom systems. Our protocol requires no continuous driving or spin-dependent potentials, and instead relies upon the population of a higher motional band to realize naturally tunable in-site exchange and cross-site superexchange interactions. As a proof-of-principle example of their utility for entanglement generation for quantum computation, we show the cross-site superexchange interactions can be used to engineer 1D cluster states. Explicit protocols for experimental preparation and manipulation of the qubits are also discussed, as well as methods for measuring more complex quantities such as out-of-time-ordered correlation functions (OTOCs).Comment: 10+7 pages, 6+1 figures. Advanced Quantum Technologies (2020

Spin Squeezing with Itinerant Dipoles: A Case for Shallow Lattices

Entangled spin squeezed states generated via dipolar interactions in lattice models provide unique opportunities for quantum enhanced sensing and are now within reach of current experiments. A critical question in this context is which parameter regimes offer the best prospects under realistic conditions. Light scattering in deep lattices can induce significant decoherence and strong Stark shifts, while shallow lattices face motional decoherence as a fundamental obstacle. Here we analyze the interplay between motion and spin squeezing in itinerant fermionic dipoles in one dimensional chains using exact matrix product state simulations. We demonstrate that shallow lattices can achieve more than 5dB of squeezing, outperforming deep lattices by up to more than 3dB, even in the presence of low filling, loss and decoherence. We relate this finding to SU(2)-symmetric superexchange interactions, which keep spins aligned and protect collective correlations. We show that the optimal regime is achieved for small repulsive off-site interactions, with a trade-off between maximal squeezing and optimal squeezing time.Comment: 4.5+5.5 pages, 4+4 figure

Spin squeezing with itinerant dipoles: a case for shallow lattices

Physic