Dynamics of an inhomogeneous quantum phase transition

TL;DR

This paper demonstrates that inhomogeneous driving of a second order quantum phase transition can suppress quasiparticle excitations, potentially improving adiabatic quantum computing by controlling the propagation velocity of the critical point.

Contribution

It provides a general theoretical prediction and analytic support that inhomogeneous quenches can reduce excitations in quantum phase transitions, with implications for quantum computing.

Findings

Excitations are suppressed when the critical point propagates below a threshold velocity.

Analytic solution in the quantum Ising chain supports the general prediction.

Inhomogeneous driving can enhance adiabaticity in quantum computers.

Abstract

We argue that in a second order quantum phase transition driven by an inhomogeneous quench density of quasiparticle excitations is suppressed when velocity at which a critical point propagates across a system falls below a threshold velocity equal to the Kibble-Zurek correlation length times the energy gap at freeze-out divided by $\hbar$. This general prediction is supported by an analytic solution in the quantum Ising chain. Our results suggest, in particular, that adiabatic quantum computers can be made more adiabatic when operated in an "inhomogeneous" way.