Christopher Monroe

Title

Quantum Magnetism from the Bottom up

Abstract

Crystals of laser-cooled atomic ions are standards for quantum information science, with psuedospins within each atom representing qubits that have unsurpassed levels of quantum coherence and can be measured with near-perfect efficiency. When spin-dependent optical dipole forces are applied to a collection of atomic ions, their Coulomb interaction is modulated in a way that allows the tailoring of spin-spin interactions that are found in theories of quantum magnetism. Recent experiments have implemented variable-range Ising interactions with up to 16 trapped ion spins, the largest system of qubits assembled to date. Direct measurements of spin-spin correlations has shown the emergence of antiferromagnetic order in this highly frustrated system as well as coherent nonequilibrium dynamics following a quench. Soon the number of spins will be high enough where no classical computer can predict the behavior of such a fully-connected quantum magnet, allowing a direct quantum simulation of the murky behavior of quantum spin liquids and spin glasses, the measurement of entanglement near a quantum phase transition, and investigations in the thermalization of a closed quantum system.