# Driving controlled entanglement in coupled flux qubits

## TL;DR

This paper investigates how periodic external magnetic fields can be used to control quantum entanglement in coupled flux qubits, demonstrating the creation and destruction of entanglement through tuning near multiphoton resonances.

## Contribution

It introduces a method to manipulate entanglement in flux qubits using external fields and provides an analytical lower bound for concurrence based on Floquet states.

## Key findings

- Entanglement can be controlled by tuning system parameters near multiphoton resonances.
- Capacitive coupling offers more robust entanglement control via ac fluxes.
- An analytical lower bound for concurrence is derived from Floquet state analysis.

## Abstract

We study the manipulation of quantum entanglement by periodic external fields. As an entanglement measure we compute numerically the concurrence of two flux qubits coupled inductively and/or capacitively, both driven by a dc+ac magnetic flux. Also we find an analytical lower bound for the concurrence, where the dominant terms correspond to the concurrence in the Floquet states. We show that it is possible to create or destroy entanglement in a controlled way by tuning the system at or near multiphoton resonances. We find that when the driving term of the Hamiltonian does not commute with the qubit-qubit interaction term, the control of the entanglement induced by the driving field is more robust in parameter space. This implies that capacitively coupled two flux qubits are more convenient for controlling entanglement through ac driving fluxes.