Speaker
Dr
Uwe-Jens Wiese
(University of Bern)
Description
Besides lattice QCD in particle physics, strongly coupled gauge theories arise,
for example, in the condensed matter physics of spin liquids, or in the quantum
information theory of Kitaev's toric code, which is a Z(2) lattice gauge theory.
Numerical simulations of gauge theories on classical computers, in particular,
at high fermion density or in out-of-equilibrium situations, suffer from severe
sign problems that prevent the importance sampling underlying Monte Carlo
calculations. Quantum simulators are accurately controllable quantum devices
that mimic other quantum systems. They do not suffer from sign problems,
because their hardware is intrinsically quantum mechanical. Recently, trapped
ions, following a laser-driven stroboscopic discrete time evolution through a
sequence of quantum gate operations, have been used as a digital quantum
simulator for particle-anti-particle pair creation in the Schwinger model.
Analog quantum simulators, on the other hand, follow the continuous
time-evolution of a tunable model Hamiltonian. Using ultra-cold atoms in
optical lattices, analog quantum simulators have been designed for Abelian and
non-Abelian lattice gauge theories. Their experimental realization is a
challenge for the foreseeable future, which holds the promise to access the
real-time dynamics of string breaking, the out-of-equilibrium decay of a false
vacuum, or the evolution of a chiral condensate after a quench, from first
principles. Quantum link models which realize gauge theories including QCD not
with classical fields but with discrete quantum degrees of freedom, are ideally
suited for implementation in quantum matter. For example, alkaline-earth atoms,
whose nuclear spin represents an SU(N) degree of freedom, naturally embody
fermionic rishon constituents of gluons. CP(N-1) models, which are toy models
for QCD, can be quantum simulated in a similar way via SU(N) quantum spin
ladders.