## Student Seminar Series

**Note:**Pizza will be served at 11:45am.

**Speaker:**Phil Weinberg, Boston University

**When:**December 4, 2019 (Wed), 12:00PM to 01:00PM (add to my calendar)

**Location:**SCI 328

**Hosted by:**Eric Boyers

*This event is part of the Graduate Student Council Events. *

Phil Weinberg (CMT)

Scaling and diabatic effects in quantum annealing with a D-Wave device

We discuss quantum annealing of the two-dimensional transverse-field Ising model on a D-Wave device, encoded on L x L lattices with L <= 32. Analyzing the residual energy and deviation from maximal magnetization in the final classical state, we find an optimal L dependent annealing rate v for which the two quantities are minimized. The results are well described by a phenomenological model with two powers of v and L-dependent prefactors to describe the competing effects of reduced quantum fluctuations (for which we see evidence of the Kibble-Zurek mechanism) and increasing noise impact when v is lowered. The same scaling form also describes results of numerical solutions of a transverse-field Ising model with the spins coupled to noise sources. We explain why the optimal annealing time is much longer than the coherence time of the individual qubits.