Physics (Internal)

Counterdiabatic and inhomogeneous driving in lattice gauge quantum computing and heat engines

This event is part of the Condensed Matter Theory Seminar Series.

We present a coherent counter-diabatic quantum protocol to prepare ground states in the lattice gauge mapping of all-to-all Ising models (LHZ) with considerably enhanced final ground state fidelity compared to a quantum annealing protocol. We make use of a variational method to find approximate counter-diabatic Hamiltonians that has recently been introduced by Sels and Polkovnikov [Proc. Natl. Acad. Sci. 114, 3909 (2017)]. The resulting additional terms in our protocol are time-dependent local on-site y-magnetic fields. A single free parameter is introduced which is optimized via classical updates. The protocol consists only of local and nearest-neighbor terms which makes it attractive for implementations in near term experiments. We further present an inhomogeneous driving protocol in LHZ with modified transverse fields with improved ground state fidelity and enlarged minimal energy gaps. The inhomogeneously driven transverse field introduces an additional time-dependent parameter that improves the efficiency of the method. For the 2D lattice gauge model LHZ we analytically derive the free energy term and numerically verify it. At last, the application of these counter-diabatic terms in the field of quantum heat engines to speed up a quantum Otto heat engine will be presented.