Driving of an open quantum system at finite temperature across first- and second-order quantum phase transitions

TL;DR

This paper investigates how driving an open quantum system of qubits at finite temperature across quantum phase transitions can improve ground state preparation fidelity, using nonperturbative dynamics with a heat bath.

Contribution

It introduces a nonperturbative approach to analyze driven open quantum systems at finite temperature near quantum phase transitions, highlighting the role of avoided crossings and heat bath effects.

Findings

Heat bath can enhance ground state fidelity during driving.

Specific driving paths influence the effectiveness of state preparation.

Avoided crossings affect the dynamics around phase transitions.

Abstract

An open fully connected system of qubits at nonzero temperature is driven within a finite time interval along various paths in the space of its control parameters. The driving leads across finite-size precursors of first- and second-order quantum phase transition from factorized to entangled ground-state phases, aiming at the preparation of the complex ground state of the system at the final parameter point with maximal fidelity. During the drive, the system is coupled to a heat bath at a constant temperature, the dynamics being determined in a nonperturbative way by the method of Hierarchical Equations of Motion. It is shown that the presence of the heat bath in combination with specific patterns of avoided crossings affecting the ground and excited states in the parameter region around the quantum phase transition may considerably improve the fidelity of preparation of the target ground state.