AQC 2016 - Inhomogeneous Quasi-adiabatic Driving of Quantum Critical Dynamics

A Google TechTalk, June 27, 2016, presented by Masoud Mohseni (Google) ABSTRACT: We introduce an inhomogeneous protocol to drive a weakly disordered quantum spin chain quasi-adiabatically across a quantum phase transition and minimize the residual energy of the final state. The number of spins that simultaneously reach the critical point is controlled by the length scale of the inhomogeneity in which the magnetic field is modulated, introducing an effective size that favors adiabatic dynamics. The dependence of the residual energy on this length scale and the velocity at which the magnetic field sweeps out the chain is shown to be non-monotonic. We determine the conditions for an optimal suppression of the residual energy of the final state and show that inhomogeneous driving can outperform conventional adiabatic schemes based on homogeneous control fields by several orders of magnitude. Presented at the Adiabatic Quantum Computing Conference, June 26-29, 2016, at Google's Los Angeles office.