Quantum Simulation of One-Dimensional Fermions

Quantum simulation is the art of emulating a target quantum system with another, more programmable quantum system. For example, atoms in potential energy landscapes controlled by laser light can be used to simulate the behavior of electrons in exotic materials. A scientific benefit of quantum simulation is that new knowledge about dynamics in the target system can be learned in the near term from a dedicated quantum simulator apparatus with tunable parameters. This approach is complimentary to building a more universal programmable digital quantum computer, which is a more expensive and long-term challenge. This project, in particular, will utilize a dedicated quantum simulator apparatus with ultracold spin 1/2 atoms confined to one dimension to serve as an emulator for electrons in nanowires such as those found in DNA and carbon nanotubes, as well as in certain molecular conductors and new types of superconductors. A quantum simulator apparatus based on ultracold fermionic lithium atoms will be improved and utilized to explore the impact of several tunable parameters, such as atom-atom interaction strength, lattice hopping energy costs, ensemble temperature, density, dimensionality, geometry, and spin polarization, to learn more about phases of matter and the dynamics of excitations in model systems that are relevant for condensed matter physics. Because the Fermi surfaces exhibited by these low-dimensional systems are highly restricted, they are also highly correlated, so unlike the usual Fermi liquids in 3D, the 1D liquids have linear dispersion relations at low energies, which are separate for the charge-density wave compared to the spin-density wave. Experimental methods used in this project such as Bragg spectroscopy and rf spectroscopy will enable new investigations of the low-energy excitations of model Hamiltonians, including the Tomonaga-Luttinger liquid (repulsive interactions), the Luther-Emory liquid (attractive interactions), and the 1D Hubbard model. This experiment will also study the role of Quantum Criticality and the FFLO effect. This is important for the progress of science because understanding new forms of superconductivity can lead to advances in condensed mater physics, new applications for quantum simulators, and opportunities for new technology development. For example, a superconductor that is robust against an internal magnetic field may have important applications for high field magnets. In addition to connections to superconductivity, FFLO physics may also be relevant to quark matter that is speculated to occupy the cores of neutron stars. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.